Black Max info?

[oldskier]

I have what the prev. owner said is a 1977 (76?) 175 Black Max. it has a straight lower unit, (I.E., as viewed from the side no 'cut in' below the cav plate.)

I have been trying to get familiar with the jargon regarding Mercs here, like displacement, 2.0, 2.5. 2.6 3.0, etc. Still don't know what this engines displacement is. Also gear ratio. The s/n is 4301631. As far as I know it is box stock.



Can someone ejumacate me?

[oldskier]

Followup question...what year parts are interchangeable for this year, such as what year powerheads and lowers fit this mid?

[Raceman]

'76 & '77 V6 Mercs were virtually identical. There was a change in the shape of the front of the gearcase somewhere back then because the blowout problem with the original '76 1750 was severe. I can't remember exactly when that change occured.

All '76 & '77 V6 Mercs were 2 liter (122 cu. in.) displacement and all had cast iron bores. These were heavy cyl's, cast in the block and made the little 2 liter motors heavier than the 2.4's that came along in '78 rated at 200 HP. The 2.4's of that era had NO cast iron or steel liners and were simply chrome plated alum. cyl's.

Any 2, 2.4, or 2.5 liter gearcase all the way up to present will bolt directly to your mid, assuming the one you're trying to interchange is the same lenght. There could be some differfences in water tube diameter if you get some of the later high perf stuff, like a late sportmaster for instance, but it's easily adaptable.

The same could be said for powerhead swaps, EXCEPT there are several different exhaust port shapes. The bolt patterns would all be the same, but the exhaust holes wouldn't line up, and the early 175's didn't match ANYTHING later on. The good news is that the two piece plates are readily available, so a powerhead switch is easy with those two additional pieces.

As far as the rest of your interchangeability questions, Merc hasn't made any 2.6 liter engines, and the 3 liter stuff is a whole different family and nothing interchanges.

[Raceman]

I may've edited it back in when I added some more interchange info, AFTER you posted again, but the early 175's were 2 liter (122 cu in).

One more thing........... the motor mounts in those engines are EXTREMELY soft/floppy. If somebody hasn't put solid mounts in it they're essential to run it on a light/fast boat like a Viper. Properly adjusted dual cable steering, foot throttle, kill switch, AND QUALITY LIFE JACKET are VERY important also. You need to spend A LOT of time in the seat of that boat before you try and find it's limits. They're a handful with a V6 and not for the inexperienced.

[rjdubiel]

sorry to aks this in your thread, but i might as well. i have a 1978 175hp merc, this is a 2.0 also correct? oldskier, i will try to get a pic of my lower. i would like to know when the change came to help prevent blowout. i would think that if my motor dies this summer i will buy a newer 200 hp. the trim is slow on my 1978 and seems that it is "loose" when compaired to a newer 3 ram clamp. also having the hp rated at the prop instead of the powerhead would be nice, as i would think a new 150 hp motor is about the same at the prop as my 1978 175hp motor at the prop:confused:

thanks
RJ

[transomstand]

The change was made in 1977 on the lower unit casting. All those engines are a problem with parts interchangeability. With the exception of the lower unit, most everything is different. If a major problem develops, it's probably best to look to a replacement, rather than try to repair. After 1982, V-6 parts become much more interchangeable, and much more plentiful.

Pete

[oldskier]

Raceman, Thanks, Yes I posted before the edit...

I'm just trying to get oriented regarding this engine and the jargon here. So this is a 2.0 cast iron block, I would assume it is an easier block to build if necessary, could be bored, no sleeves or plating needed?

If I get the boat back in the water, I'll be baselining, may do some mounts and a nosecone after I feel like it might run a few more hours. Need to run compression test to get an idea of condition. Starts easily and runs very well, no coughs sputters or cutting out, but still could be on it's last leg...

Believe me, have heeded your notes of caution, thanks again. Hot foot on the way, deadman switch and trim on wheel will go in before next launch. I'm VERY nervous about the blowout issue, but not spending money to avoid it until I know it will go blowout speeds...(60+mph?)

I guess I won't be the first fool to find out the hard way, but a cone and LWP for the old girl seems pricey until I know what she's got left in her.

At least the boat made it up to 2007 without destroying itself, didn't find any blood stains in the cockpit. No cone, no hotfoot, no steering mount trim, no plate. Does have dual opposed ride guide and a torque tab. 26 small ear.

Thanks, Bernie

[transomstand]

as i would think a new 150 hp motor is about the same at the prop as my 1978 175hp motor at the prop


I went from a 77 175, to an 85 XR2 and was dissapointed. I had the same thought about horsepower rating, but I think the old 175 was a little quicker.

Pete

[oldskier]

'Nuther idjit question, how can I determine if it has solid mounts?

[transomstand]

I guess I won't be the first fool to find out the hard way, but a cone and LWP for the old girl seems pricey until I know what she's got left in her.



No you won't:D

It blows out at about 71-72:D

The good part for me was the Ventura blows out gently, and you can feel it coming, starts to shake a little like an aircraft about to stall. I don't think the Viper is quite so forgiving.

[transomstand]

'Nuther idjit question, how can I determine if it has solid mounts?

You can see the lowers by removing the plastic covers, no such luck on the uppers, powerhead needs to come off.

[oldskier]

TS, Gee I feel MUCH more secure now! Did you have to write that in RED?

[oldskier]

I'll take the covers off again, did it for the repaint, but didn't pay attention...

[nelsoncat]

you should be able to tell by grabbing the power head and turning it side to sie. If there is movement of the motor without the steering arm moving then the mounts are rubber, the more it moves the more rotted the rubber. My problem with the solids is getting the 2 piece plate to seal around them. Every thing needs to be clean and true. I had to redo a couple due to no water pressure and exhaust in the water cavity. A one piece plate is really the way to go but more pricy and there are a few other issues relating to water routing on a fishing motor that others with more knowledge could help with.
Craig

[rjdubiel]

I went from a 77 175, to an 85 XR2 and was dissapointed. I had the same thought about horsepower rating, but I think the old 175 was a little quicker.

Pete

pete, did you go to an 85 xr2 175hp?

bernie, i am getting these low water scoops for my motor, merc number 17280A2. if the motor lives through next summer or not it will be replaced in the summer of 2009 with a 200 hopefully:D if it dies this summer i guess the good old credit card will be buying me a newer motor. then i get to give the 1978 powerhead rebuild a try:eek:

[transomstand]

pete, did you go to an 85 xr2 175hp?


XR2's were advertised as 150's, but reportly made about 165 hp at the prop.

[Raceman]

The block isn't cast iron itself, just heavy cast iron cyl's cast into the aluminum. These include the transfer ports, so there's a lot more to em than just a sleeve.

These engines are actually very durable, and I'm not exactly sure what TS is referring to with the lack of parts interchangeability. The electricals interchange as do the carbs (basically speaking on the carbs). Change the previously mentioned exhaust plates and any V6 powerhead below 3 liter is a direct bolt on.

As far as blowout, I wouldn't want any part of blowing out in a Viper with a V6 on it. I believe the earliest design V6 case will blow out on that boat somewhere in the 60's and if you don't have a lot of experience gathering an out of shape V bottom back up at speed, it may very well be ugly.

[Raceman]

A couple of comments on solid mounts:

Don't even think about just doing the lowers without doing the uppers also. Making one end rigid while letting the other end floppy will break parts, and it won't be the motormounts that break.

I've never had a problem with leakage at the uppers and don't see how it would happen UNLESS: 1. upper mounts are made slightly too big. (I have seen that with one set, but didn't use em) 2. extreeme nastyness in mount seats in the upper plates. 3. bad gasket between upper plates.

[oldskier]

if you don't have a lot of experience gathering an out of shape V bottom back up at speed, it may very well be ugly.

WELLLL, I may get the experience, maybe just a marker where I went down....

RJ, Have you done a compression check on yours yet? If you do, I'd be interested in the numbers. I plan on doing mine once it's re-rigged.

I'm gonna try to get the scoops too, before I put it in the water.

[R.I.P.]

I have a 2.5 off shore 1987 is this a black max? and what years are interchangable in the 2.5 200hp

[transomstand]

The block isn't cast iron itself, just heavy cast iron cyl's cast into the aluminum. These include the transfer ports, so there's a lot more to em than just a sleeve.

These engines are actually very durable, and I'm not exactly sure what TS is referring to with the lack of parts interchangeability. The electricals interchange as do the carbs (basically speaking on the carbs).



True, the electrics and carbs will swap, but little else, the early carbs have the round shape bowls, unlike the later squared off bowls, they are impossible to get floats for. Block, heads, exhaust plate, tuner, driveshaft housing, clamp, trim parts are all different, and no BIA bolt pattern. I don't think it's worth the effort to save one if it's in rough shape.
I did this swap just a few years ago(to a later model engine), and was suprised at how much needed to be changed.

Pete

[transomstand]

I have a 2.5 off shore 1987 is this a black max? and what years are interchangable in the 2.5 200hp
Did you mean 97? In 87 it was all still 2.4's.

[R.I.P.]

a 1987 offshore 2.5 this is what is on the cover could it be a 1989?

[geeforcem]

I went from a 77 175, to an 85 XR2 and was dissapointed. I had the same thought about horsepower rating, but I think the old 175 was a little quicker.

Pete

I put a '77 1750 powerhead onto a later model midsection and added a set of wh22 carbs. other than that it's stock. I have it on my '83 Laser LTV. It turns an ET cut 26" chopper to 6000 RPMs...

I was thinking about putting together an XR2 style 2.0... what was the difference that u felt between the 2 engines?

i do love the way the 1750 sounds with no exhaust liner...

[transomstand]

a 1987 offshore 2.5 this is what is on the cover could it be a 1989?

The first 2.5's were 90-91

[transomstand]

I put a '77 1750 powerhead onto a later model midsection and added a set of wh22 carbs. other than that it's stock. I have it on my '83 Laser LTV. It turns an ET cut 26" chopper to 6000 RPMs...

I was thinking about putting together an XR2 style 2.0... what was the difference that u felt between the 2 engines?

i do love the way the 1750 sounds with no exhaust liner...

I had hoped the XR2 would be a little faster, but I think it was slightly slower than the old 175. I changed to the heavier single ram clamp at the same time, which definitely hurt the top speed, and didn't allow a direct comparison. I think the two engines are about equal, unless you heavily modify the XR2, it's probably not worth the trouble.

Pete

[Raceman]

I changed to the heavier single ram clamp at the same time, which definitely hurt the top speed, and didn't allow a direct comparison.
Pete

Slight differences in weight won't make a measureable difference in top speed, especially when it's hung off the transom. You'll find in many cases that an extra person in the boat won't even hurt if you'll get em to go sit in the rear of the boat in the middle.;) Of course that's not true in all cases, but adding 10, 20 or 30 lbs in an engines weight woudln't be measureable in anything except ET/drag race conditions in 99.99 percent of applications.

[nelsoncat]

mine was definitely a case of an oversized solid mount, it wouldn't allow the 2 halfs to seat together. Not exactly sure what the second's problem was.

[rjdubiel]

WELLLL, I may get the experience, maybe just a marker where I went down....

RJ, Have you done a compression check on yours yet? If you do, I'd be interested in the numbers. I plan on doing mine once it's re-rigged.

I'm gonna try to get the scoops too, before I put it in the water.

bernie,
i only took the cover off the motor to get the lifting ring on and put the motor on a stand. it is all stock except a new coil the old owner said. i havent done a comp test, i will do one also this spring when the boat and motor meet again:D

[transomstand]

Slight differences in weight won't make a measureable difference in top speed, especially when it's hung off the transom. You'll find in many cases that an extra person in the boat won't even hurt if you'll get em to go sit in the rear of the boat in the middle.;) Of course that's not true in all cases, but adding 10, 20 or 30 lbs in an engines weight woudln't be measureable in anything except ET/drag race conditions in 99.99 percent of applications.


I'm going to disagree on the weight difference, after changing the clamp, I found the difference to be huge. Maybe most people wouldn't notice, but the pad rode much deeper in the water after the change.

Pete

[R.I.P.]

Sorry here is a set of pics.The guy who sold it to me said it was a 1987 200 merc offshore .
What do you guys think?

[transomstand]

It's not an 87, if it has the right cowl. That's the problem with older engines, stuff gets switched around. Looks like an early 90's 2.5 cowl.

Pete