Mad EFI mid

[25two.stroke]

With the engine back together I feel comfortable telling this story. It is assembled EXACTLY how Todd at Mad EFI says to do it, so if anything breaks again then he had better take responsibility.
So here it goes:
15" 300x on an allison 2003xb - 110 mph boat
Engine was assembled originally by DBR and used a cut down 20" fishin can. This setup lasted about 5 years and then the lower unit bolts backed off and with the lower unit running loose it cracked the front of the midsection across right down the center of the mounting studs where its thin. The propshaft seal had failed in the lower unit and water wiped out the propshaft needle bearing. Not sure if that cause excessive vibration that backed the mounting bolts off or if it was coincidence the two failures happened at the same time. The driveshaft was 2 piece and when the lower came down it stripped out the driveshaft at the coupler.

I replaced the driveshaft with a solid shaft cut and resplined by Chris Carson. The owner of the boat opted for a mad EFI mid since they were readily available, one piece, and had a good reputation. We didn't have to find a 20" can and have it cut.

We got the parts, and upon unboxing the mid I noticed the bolt holes where the adapter plate bolts to the driveshaft housing were not centered in the casting. The threads for one bolt were dangerously close to the driveshaft cavity to where threads were almost poppin out. I looked closer at the whole upper hole pattern and it was not centered in the casting at all. It was about 1/16" shifted over to the starboard. I thought, "thats odd, but I guess it doesn't matter. just bad casting. And if the lower bolt pattern is aligned to the upper bolt pattern then its all good."



pics above taken after we tore the engine apart...^

I looked at how the can was made and figured that it was cast and then jigged up somehow and a cnc cleaned up the inside and drilled all the holes, so the whole bolt pattern was just not centered in the casting and it would be okay. We put the powerhead on and then the lower unit. The lower unit had a tad of trouble going up the last 1/2" and I didn't think much of it cause junk on the splines and on the dowell pins cause that on almost every water pump job I do; and I do multiple daily.

Owner drove the boat two times up to 108 and put about 120 miles on it. On his third trip out he called me from the water saying he lost all his gears. He though he blew the lower unit up I put it together. I asked him if the engine started he said yes. I asked if the engine pumped water he said no. I knew immediately he snapped the driveshaft.

We pulled the powerhead that night and found a stripped driveshaft. I also noticed that the driveshaft was not coming up through the center of the hole in the adapter plate. In fact, it was rubbing on the casting of the adapter plate it was so far off center. I did not notice this on first assembly because we put the powerhead on before the lower unit. The amount that the driveshaft was off center is about the same amount the bolt pattern was off in the casting.

I thought to myself, "I wonder if when the lower backed off the first time if it warped the mating surface of the lower unit, so the lower isn't square to the powerhead anymore." To test this, I got a BRAND NEW lower unit from mercury and bolted it up to the midsection: same thing.



Driveshaft touching the one side of the adapter plate and about 1/8" away from the other side.



I called Chris Carson and asked if he ever had that experience or knew of anyone who had with a mad EFI mid. He said he had not ever heard of that with a mad EFI mid. All he could recall was 3 instances of his driveshafts stripping/breaking. One was on a welded mid and I can't recall what the other two were but it was a twin engine boat and both shafts of his stripped. In each of the 3 instances either the driveshaft was not centered or it was centered and coming up to the powerhead a few degrees off of plumb. He took me back decades in stories to when OMC had alignment issues in their fishing motors which resulted in numerous driveshafts snapping right below the water pumps. Their factory solution ended up being a type of universal joint/coupler by the water pump that would allow just enough wobble for the driveshaft to pivot around and stay engaged despite a slight misalignment. He said that back then OMC allowed a driveshaft to be like 0.002" out of center for a solid shaft to live, otherwise one of those 2 piece shafts was needed. The shafts would shatter within an hour or two of run time if an out of center lower+mid was bolted to the powerhead.

I measured the misalignment in the mad EFI mid and it was 0.019" different from one side to the other: so 0.0095" off center. THATS MORE THAN 1/16 OF AN INCH!

I called todd at mad EFI and told him what we had going and my suspicion about his cnc cutting the bolt pattern off center.

He said, "That is impossible.'
His words.
He said I was correct about how they make the mids. They cast them, make the lower unit bolt pattern, bolt the lower to a jig where the cnc scans the housing and finds center BASED OFF OF the lower unit bolt patter. So even if the casting is off, the lower unit bolts and the powerhead bolts will be dead nuts centered. He said the reason the threads were almost popping through the side is cause the total housing bolt pattern was not centered in the casting, but that would not cause any failures.

I agree, if the whole thing was off center it wouldn't really matter.

I sent him the pictures of the driveshaft coming up out of center and he said "I see nothing wrong, that is not an issue. When the powerhead is bolted to it then it will be pulled back to center and its fine. The failure was due to the driveshaft splines being weak and not heat treated like Mercury's."

^the above may be paraphrased because this conversation was more than a month ago^

However, he said misalignment is not an issue and if I put a mercury cut and welded driveshaft made by Craig Collabella then all out problems would go away. I'm a semi smart guy, I'm a marine mechanic, I was a designer/fabricator in the past and I worked in highrise construction, building litigation, etc... I've seen a lot of stuff and I know hoe stuff is built. I know that this mid aint right. However he said it is quote "impossible" for his cnc to make a mistake. Which I know is BS because I worked with CNCs for 3 years and have done autocad, drafting, 3d printing, and 3d modelling for 8 years. I know machines can make mistakes even though that is rare.

I called Chris Carson back to see his opinion and his was the same as mine, and the same as 3 or 4 other engine builders local here that I had take a look at it. We all say off center that much is not acceptable at all. However, to give Todd the benefit of the doubt, I put the whole engine back together how he said. I send the shaft to craig, got it back, built the lower and put the engine back together. We are set to do a water test in 10 days or so.

The original Chris Carson splines, sure they are softer than mercury, but I run them, everyone I know around here with 15" mids run cut and splined shafts...its never been an issue here till now. It did take 120 miles for it to fail, and sure the hard mercury splines probably will last longer. So I expect the motor to run good for 4 or 5 trips. But I am 90% sure its gonna fail again, maybe not at the powerhead splines like the first case, but its gonna snap that shaft at the weakest point: probably below the water pump like on an OMC. What is ya'lls opinion on this matter?



3.218" from the outside of the powerhead stud hole to the driveshaft on the port side

3.058" from the outside of the powerhead stud hole to the driveshaft on the starboard side

I am not one to stir up trouble, but I just kind feel like this is all garbage.

[25two.stroke]

[2thelake]

25 finally some info on what happened!!!

I had snapped my 20” shaft on my LU below the water pump. I’m not sure how that happened but I went on this site and found Craig Collabella! So happy I found him since his shop is right up the highway from Melbourne. Great guy! Texted me every single step of the way until my sporty was all rebuilt! Even invited me to have a beer with him after he closed shop for the day! Highly recommend.

After I got back I bolted my Sporty up to the motor and it looks to me like my LU is misaligned to my factory 20” mid. I don’t have any pictures, can maybe get some soon…but the grey part of the SM is not aligned with the tip of the aft part of the factory mid it’s maybe off by a 1/16 of an inch maybe even less then that.

Have you ever had that problem 25? Where the LU looks fine but when you bolt it up to the mid it snugs up fine but it isn’t centered when you look at it from the aft end of the boat looking forward. Just how much misalignment can be tolerated from the lower unit to the midsection? Are these problems of drive shafts snapping below the water pump due to midsection or a possibly bent LU? My splines were not stripped out that go into the motor. The break was so clean that it looked to me like someone to a razor blade to the shaft and cut it.

im not trying to defend or bash anyone on here as my thought was that I’m just gonna buy a new midsection and clamp and then see how she goes from there. I ran my boat like that for the rest of the summer and had no problems.

just want to know what can cause driveshafts to break below the water pump and what can cause drive shafts to despline in the powerhead? Like other then wave bashing and going airborne without throttling back what causes it? How do you even measure to tell if your mids and lowers are out of alignment?

[2thelake]

When looking at this part it looks to be off center? Is that a problem?

[2thelake]

Looks like I got a casting from your batch and one casting from another like you said after you look for that threaded hole that you pointed out!

[WaterZebra]

With the engine back together I feel comfortable telling this story. It is assembled EXACTLY how Todd at Mad EFI says to do it, so if anything breaks again then he had better take responsibility.
So here it goes:
15" 300x on an allison 2003xb - 110 mph boat
Engine was assembled originally by DBR and used a cut down 20" fishin can. This setup lasted about 5 years and then the lower unit bolts backed off and with the lower unit running loose it cracked the front of the midsection across right down the center of the mounting studs where its thin. The propshaft seal had failed in the lower unit and water wiped out the propshaft needle bearing. Not sure if that cause excessive vibration that backed the mounting bolts off or if it was coincidence the two failures happened at the same time. The driveshaft was 2 piece and when the lower came down it stripped out the driveshaft at the coupler.

I replaced the driveshaft with a solid shaft cut and resplined by Chris Carson. The owner of the boat opted for a mad EFI mid since they were readily available, one piece, and had a good reputation. We didn't have to find a 20" can and have it cut.

We got the parts, and upon unboxing the mid I noticed the bolt holes where the adapter plate bolts to the driveshaft housing were not centered in the casting. The threads for one bolt were dangerously close to the driveshaft cavity to where threads were almost poppin out. I looked closer at the whole upper hole pattern and it was not centered in the casting at all. It was about 1/16" shifted over to the starboard. I thought, "thats odd, but I guess it doesn't matter. just bad casting. And if the lower bolt pattern is aligned to the upper bolt pattern then its all good."



pics above taken after we tore the engine apart...^

I looked at how the can was made and figured that it was cast and then jigged up somehow and a cnc cleaned up the inside and drilled all the holes, so the whole bolt pattern was just not centered in the casting and it would be okay. We put the powerhead on and then the lower unit. The lower unit had a tad of trouble going up the last 1/2" and I didn't think much of it cause junk on the splines and on the dowell pins cause that on almost every water pump job I do; and I do multiple daily.

Owner drove the boat two times up to 108 and put about 120 miles on it. On his third trip out he called me from the water saying he lost all his gears. He though he blew the lower unit up I put it together. I asked him if the engine started he said yes. I asked if the engine pumped water he said no. I knew immediately he snapped the driveshaft.

We pulled the powerhead that night and found a stripped driveshaft. I also noticed that the driveshaft was not coming up through the center of the hole in the adapter plate. In fact, it was rubbing on the casting of the adapter plate it was so far off center. I did not notice this on first assembly because we put the powerhead on before the lower unit. The amount that the driveshaft was off center is about the same amount the bolt pattern was off in the casting.

I thought to myself, "I wonder if when the lower backed off the first time if it warped the mating surface of the lower unit, so the lower isn't square to the powerhead anymore." To test this, I got a BRAND NEW lower unit from mercury and bolted it up to the midsection: same thing.



Driveshaft touching the one side of the adapter plate and about 1/8" away from the other side.



I called Chris Carson and asked if he ever had that experience or knew of anyone who had with a mad EFI mid. He said he had not ever heard of that with a mad EFI mid. All he could recall was 3 instances of his driveshafts stripping/breaking. One was on a welded mid and I can't recall what the other two were but it was a twin engine boat and both shafts of his stripped. In each of the 3 instances either the driveshaft was not centered or it was centered and coming up to the powerhead a few degrees off of plumb. He took me back decades in stories to when OMC had alignment issues in their fishing motors which resulted in numerous driveshafts snapping right below the water pumps. Their factory solution ended up being a type of universal joint/coupler by the water pump that would allow just enough wobble for the driveshaft to pivot around and stay engaged despite a slight misalignment. He said that back then OMC allowed a driveshaft to be like 0.002" out of center for a solid shaft to live, otherwise one of those 2 piece shafts was needed. The shafts would shatter within an hour or two of run time if an out of center lower+mid was bolted to the powerhead.

I measured the misalignment in the mad EFI mid and it was 0.019" different from one side to the other: so 0.0095" off center. THATS MORE THAN 1/16 OF AN INCH!

I called todd at mad EFI and told him what we had going and my suspicion about his cnc cutting the bolt pattern off center.

He said, "That is impossible.'
His words.
He said I was correct about how they make the mids. They cast them, make the lower unit bolt pattern, bolt the lower to a jig where the cnc scans the housing and finds center BASED OFF OF the lower unit bolt patter. So even if the casting is off, the lower unit bolts and the powerhead bolts will be dead nuts centered. He said the reason the threads were almost popping through the side is cause the total housing bolt pattern was not centered in the casting, but that would not cause any failures.

I agree, if the whole thing was off center it wouldn't really matter.

I sent him the pictures of the driveshaft coming up out of center and he said "I see nothing wrong, that is not an issue. When the powerhead is bolted to it then it will be pulled back to center and its fine. The failure was due to the driveshaft splines being weak and not heat treated like Mercury's."

^the above may be paraphrased because this conversation was more than a month ago^

However, he said misalignment is not an issue and if I put a mercury cut and welded driveshaft made by Craig Collabella then all out problems would go away. I'm a semi smart guy, I'm a marine mechanic, I was a designer/fabricator in the past and I worked in highrise construction, building litigation, etc... I've seen a lot of stuff and I know hoe stuff is built. I know that this mid aint right. However he said it is quote "impossible" for his cnc to make a mistake. Which I know is BS because I worked with CNCs for 3 years and have done autocad, drafting, 3d printing, and 3d modelling for 8 years. I know machines can make mistakes even though that is rare.

I called Chris Carson back to see his opinion and his was the same as mine, and the same as 3 or 4 other engine builders local here that I had take a look at it. We all say off center that much is not acceptable at all. However, to give Todd the benefit of the doubt, I put the whole engine back together how he said. I send the shaft to craig, got it back, built the lower and put the engine back together. We are set to do a water test in 10 days or so.

The original Chris Carson splines, sure they are softer than mercury, but I run them, everyone I know around here with 15" mids run cut and splined shafts...its never been an issue here till now. It did take 120 miles for it to fail, and sure the hard mercury splines probably will last longer. So I expect the motor to run good for 4 or 5 trips. But I am 90% sure its gonna fail again, maybe not at the powerhead splines like the first case, but its gonna snap that shaft at the weakest point: probably below the water pump like on an OMC. What is ya'lls opinion on this matter?



3.218" from the outside of the powerhead stud hole to the driveshaft on the port side

3.058" from the outside of the powerhead stud hole to the driveshaft on the starboard side

I am not one to stir up trouble, but I just kind feel like this is all garbage.

Take a look at your top photo. The lug profiles (thickness) are different from "core shift" at the foundry. Not a big deal for MAD EFI based on numbers cast but would be unacceptable for Mercury Marine. Matching engine block stud bores to gearcase bolt patterns while keeping the driveshaft axis coaxial to prevent runout side load failures can be tricky. Mercury Marine HiPerf knows this. It would be interesting to see MAD EFI's "jig" for putting in the second set of bores and how the top and bottom end plane surfaces are kept co-planer and to what tolerance? Can the adapter plate be reworked to provide a bigger clearance bore for the driveshaft? Is there evidence of "printing" on the driveshaft O/D?

[ChrisCarsonMarine]

Just want to know what can cause driveshafts to break below the water pump and what can cause drive shafts to despline in the powerhead? Like other then wave bashing and going airborne without throttling back what causes it? How do you even measure to tell if your mids and lowers are out of alignment?
I believe shaft breakage below the pump and spline failure are usually due to two different causes,sometimes found together sometimes alone.
As OMC learned in the late 70's,the driveshaft must aim accurately at the crankshaft,allowed .002,runout,or the shaft will(may) fatigue at the point of highest flex...immediately above where the shaft is held securely in a rather robust combination of roller needle bearings and thrust bearings right below the water pump.The amount of misalighnment is directly related to the lifespan of the doomed shaft,witnessed personally many times.Prior to the two piece shaft,with a loose spline sort of CV joint,some of the shafts were thinned from 7/8 to 5/8 over most of their length to allow some easier flex spread out over the length of the shaft so as to not concentratate the flex at the pump base bearing exit,helped,but did not solve the problem.Anyway,understanding that the shaft is turning 75 times a second at a mere 4500 rpm cruiseing speed you should realize there is a lot of flexing going on,and the greater the flex,the faster the failure,which,by the way,did not occure on the test run but might take 50 or 100 or more hours.
Our MERC factory mids seem pretty well made,and usually when i find a misalighnment it's due to a lower unit being run loose,and wearing the front of the mid AND lower and causing the driveshaft to "lean"backward"...This will have to be corrected,or you'll probably break a shaft...And the only way to check is with the powerhead off and gearcase on to be sure the shaft is centered in the adapter plate hole.And realize,the shorter the shaft,the greater the out of alighnment flexes the shaft.
AS TO spline failure...Don't see it often at all...If someone says"I'vs seen lots of Chris' shaft splines fail",all I can say is I haven't heard of em...and it seems like I would have,Show me.I now know of 4.
In all 4 cases the failure occured within a couple hours and the splines were ground up,not sheared.In all cases there has been a severe (my opinion) misalighnment with the mid,either not aiming the driveshaft at the crankshaft,or not mounting the crankshaft (powerhead) perfectly perpendicular(leaning forward,aft,or to one side.This misalighnment places the load from crank splines to shaft splines on the top of one spline,and the bottom of one spline on the opposite side of the shaft.No longer is the full face of all the splines carrying the load,but the load is being carried by the ever changing top and bottom of 2 splines...instead of the desighners full faced 13 splines,and they will quickly be chipped and worn away,starting at the top and bottom,and meeting in the middle.This is not rocket science,or mysterious...just mechanical common sense.
Regarding shafts and splines...
MERC often spin welds a hardened splined steel tip to their stainless shafts,some are just splined stainless.
The flood of aftermarket shafts we are seeing now do not have hardened steel splines,and also do not appear to be heat treated/hardened...likewise with the MERC all stainless top shafts.
All the shafts I spline do get heat treated and hardened,and hold up well,however they are not as hard as the spun welded tips,and in normal and high performance use there are no problems.
Not being a "kiss and tell"sort of guy,I will not go into all the shafts I've splined for racers and service motors alike,my customers business with me does not get broadcast without permission,and frankly I'm too busy for that stuff.I'v been doing these shafts for over 15 years,lots of em.Average 2-3 a week these days,no justified
complaints.
If putting a hardened tip on the driveshaft makes it go a while,it dosen't cure the misalighnment,just hides it a while...Wouldn't be necessary if things were straight and true...proved that hundreds of times...
I have to wonder what goes next,if run long enough...Crank splines,broken shaft,bearing failure under the pump...I know MERC mids are a lot straighter than necessary,they should relax,mid being a little crooked won't hurt anything...right,Chris

[25two.stroke]

Have you ever had that problem 25? Where the LU looks fine but when you bolt it up to the mid it snugs up fine but it isn’t centered when you look at it from the aft end of the boat looking forward. Just how much misalignment can be tolerated from the lower unit to the midsection? Are these problems of drive shafts snapping below the water pump due to midsection or a possibly bent LU? My splines were not stripped out that go into the motor. The break was so clean that it looked to me like someone to a razor blade to the shaft and cut it.


just want to know what can cause driveshafts to break below the water pump and what can cause drive shafts to despline in the powerhead? Like other then wave bashing and going airborne without throttling back what causes it? How do you even measure to tell if your mids and lowers are out of alignment?

Read Chris' post about OMC snapping driveshats below the pump due to misalignment. It also happens sometimes does to bearing failure where the lower part of the driveshaft seizes up and then the powerhead shears the shaft. The snaps dies to seizing bearings typically result in a twist to a point kinda look, not a straight shear; UNLESS you keep running it and the top spinning part of the shaft grinds it back flat due to friction.

Your off-center issue I see ALL THE TIME. Even new motors from mercury don't align right at the bottom sometimes (due to casting differences). However, the appearance isn't what matters most, and mercury knows that, all that matters is that its aligned inside. I have never seen a mercury factory engine snap a driveshaft below the pump or at the powerhead except when they were abused. 250 and 300 xs motors that frequently get jumped out of the water and the drive doesn't let off the gas (most bass fishermen eager to get somewhere even in rough weather) shear all the time at the pinion gear or at the fusion weld by the crank. You can tell when that happens because its obvious it was a sudden failure, not over time like a seizing support bearing or a misalignment. The crack is all crystalline from sudden excessive force.

In your case I would not worry about it unless you snap another shaft. Then do what I did bolt a lower unit up with no powerhead and check alignment up at the ph mounting area. Measure side to side as well as the vertical angle being square to the mating surface. <Chris can tell you how to do that if and when you need to .

[25two.stroke]

Looks like I got a casting from your batch and one casting from another like you said after you look for that threaded hole that you pointed out!

Does look like you got 2 different castings...however, if it was machined right then it won't matter. Check it before you drop the powerhead on.

[2thelake]

Does look like you got 2 different castings...however, if it was machined right then it won't matter. Check it before you drop the powerhead on.

Can you repost how would you check the midsection for alignment?

do you bolt up mid and lower and take powerhead off and measure like you did from the top then put the power head on and take the lower unit off and then hold an uninstalled drive shaft in the powerheard while you measure from the bottom with the lower unit off to compare the differences in distance from the outside of the hole to the shaft?

[KIRCHNER]

I found a simple way to to check alignment. power head off, lower on. i found a 2fft piece on ss hand rail / bow rail tubing, the I.D. fit perfectly over the dr shaft splines, showing out of the adaptor plate. lay a 2' mech square across plate, front to back,side to side. mine is leaning backward, on acut 15 mid. now im at a stand still. the mis-alignment is obvious. my mid was not cut square, i dont see a cure

[25two.stroke]

I found a simple way to to check alignment. power head off, lower on. i found a 2fft piece on ss hand rail / bow rail tubing, the I.D. fit perfectly over the dr shaft splines, showing out of the adaptor plate. lay a 2' mech square across plate, front to back,side to side. mine is leaning backward, on acut 15 mid. now im at a stand still. the mis-alignment is obvious. my mid was not cut square, i dont see a cure

Well I'm glad my post helped someone already!
Yeah don't put it together crooked it will fail like this one I'm dealing with.
You can fix your mid but its a pain in the ass. Either mill it flat or weld up and drift the holes back over if side to side if thats the issue. Neither is fun.

To check center measure from the powerhead bolt holes to the driveshaft with calipers. Triangulate off multiple holes to make verify your findings. If it seems centered but you suspect the driveshaft is not square to the powerhead you can put a flat plate across the top of the mid, drill a driveshaft sized hole in it, and then get a vise-grip or magnet dial indicator and put it on the driveshaft. Spin the driveshaft and watch the dial and see how many thousandths its leaning.

[2thelake]

Well I'm glad my post helped someone already!
Yeah don't put it together crooked it will fail like this one I'm dealing with.
You can fix your mid but its a pain in the ass. Either mill it flat or weld up and drift the holes back over if side to side if thats the issue. Neither is fun.

To check center measure from the powerhead bolt holes to the driveshaft with calipers. Triangulate off multiple holes to make verify your findings. If it seems centered but you suspect the driveshaft is not square to the powerhead you can put a flat plate across the top of the mid, drill a driveshaft sized hole in it, and then get a vise-grip or magnet dial indicator and put it on the driveshaft. Spin the driveshaft and watch the dial and see how many thousandths its leaning.

I’m a newbie at this and am still trying to understand. So with just the power head off, but mid and lower bolted up tight you rotate the shaft via prop. A dial indicator is set up to be just touching the shaft right below the splines and then zeroed. Turning the shaft will tell you by dial indicator if it is off by however many thousands. That will show if the shaft is bent or if the mid is bending the shaft. The next step is what confuses me…. Are you trying to mimic the powerheads female splined end (where the drive shaft goes into the powerhead correct? So how would you just put a flat plate on there secured with vice grips and take measurements with a dial indicator. I feel like if a shaft was being bent/misaligned it would take a lot more strength then vice grips have to hold a plate there perfectly stationary to mimic the powerhead and inturn bend the shaft. Sorry for all the questions just don’t want to make costly mistakes! Want to really figure this out!

[TraceF3]

Oh ****, I feel for you guys...

...and now I have another thing to worry about

[25two.stroke]

I’m a newbie at this and am still trying to understand. So with just the power head off, but mid and lower bolted up tight you rotate the shaft via prop. A dial indicator is set up to be just touching the shaft right below the splines and then zeroed. Turning the shaft will tell you by dial indicator if it is off by however many thousands. That will show if the shaft is bent or if the mid is bending the shaft. The next step is what confuses me…. Are you trying to mimic the powerheads female splined end (where the drive shaft goes into the powerhead correct? So how would you just put a flat plate on there secured with vice grips and take measurements with a dial indicator. I feel like if a shaft was being bent/misaligned it would take a lot more strength then vice grips have to hold a plate there perfectly stationary to mimic the powerhead and inturn bend the shaft. Sorry for all the questions just don’t want to make costly mistakes! Want to really figure this out!

Chris had me all confused for 20 min while he tried to explain to me how to do this. Its hard to explain, easy to do. Dial indicator goes on the driveshaft and points straight down towards the lower unit making contact with the steel plate. If the driveshaft is at angle the dial indictor will vary as you spin the driveshaft.