performance help

[gorillapowered]

I have a 1986 200 merc blackmax on a 17 action. I have been trying some different props to get this baby to fly. The engine has bob's low water nose cone, reeds, electric fuel pump. The set up is good, cmc jack plate, ect...
I am spinning a 26 chopper and cant get over 58,5900 RPM at just shy of 80mph. That is the best I got, engine up and trimmed out. I tryed a 29 pitch SRX and did worse 5600ish RPM at 77ish mph. Just because I had it, tryed a 23pitch through the hub rapture and did 6000 rpm at 74ish mph.
The engine runs like a top and did the compression when I got home today. 121-125 all 6.
What can I do for some more power in this thing???:D

[Gorilla0178]

Well I had similar perf results with mine. I was getting 60 at 5K 70 at 6K and 75 alittle bit above that I dont have the seat time to fly it past that, the motor will turn more so Im not sure what it'll get to. I know your prop is a bit worked, mine isnt so you have better numbers. Have you had it free up and fly? I've only had it up good a few times and thats when it feels like its got more. But didnt drive it too much after that....

[gorillapowered]

I always thought that if I had better conditions or go it trimmed out more, but today I had it maxed out. The motor had nothing else, wasnt bogging down or acting funny... it just was peaked out. I am hoping that I could get some more out of it.

[transomstand]

What's your propshaft height?

[gorillapowered]

with the jack plate up the prop shaft is 1.5-2 inch above the bottom of the stern. I can get the engine too high, I have to watch the height cause I will loose water pressure.

[rhickox]

Have the heads cut for 145-150 lbs of compression and try different motor heights...the extra compression should help a lot. Also have the wide open throttle timing set to 24-25 degrees....Level the boat and the motor. Measure to the center of the propshaft from level concrete, then measure from level concrete to the center of the pad on the boat. That is the correct way to measure propshaft heighth

[gorillapowered]

Thanks, I heard alot of guys talking about having there heads cut. Makes a big difference?? What is a rough estimate on what that coasts??

[rhickox]

Give Mike Clemmons a call at Outback Outboards. Are they one piece or 2 piece heads???? If they are 2 piece heads, you would be better off putting a set of 1 piece heads on it.. Give him a call @ 706-564-6372....

[transomstand]

To give you a baseline. My boat turns a 30 Chopper about 6500 (1:87 gear), propshaft 1 1/2" above the bottom of the pad. I would expect to turn a 26 well over 7000.

Bone stock 2.4, 22 degrees of timing, stock heads, pig rich.

[HStream1]

Running a prop cal. Something doesn't compute. At 10% slip 5850 rpm's 26 pitch your top speed can't be 80 mph's. Unless your prop slip is way lower than 10% (highly unlikely). Even at 3% slip you would only see 74/75 ish.

Pitch of Prop X Engine RPM
______________________ = Theoretical Speed
Gear Ratio X 1056

So in your case;

26 X 5850 (I split the difference) = 152100
__________________________________ = 77.023 Theorectical speed

1.87 X 1056 = 1974.72

77.023 - % prop slip (10%) = (69.3 MPH vs 80)

Your 29 & 5600 rpm numbers are close (74 mph vs 77)

Your 23 & 6000 rpm numbers are off (62.9 vs 74)

In theory for every 1" of pitch you up or down you should see a RPM change of between 200/300 rpm's.

That doesn't seem to be the case here based on what you posted.

Regardless the biggest bang for the buck is heads but they alone will not have much affect on top end. They will allow you to spin a higher pitch prop. But heads alone won't give you higher RPM's that will amount to anything.

Might want to check your speedo and or tach. You can also have good compression and not so good leakdown. A poor leakdown can have negative affects on overall performance.

I'm not trying to bust you here. Just trying to understand why the numbers don't compute.

[Gorilla0178]

I did the prop slip calc on my speeds, and with a stock 26pitch chopper, I'm right at 10%, 5000 rpm is right at 60, and 6000 rpm is right at 70, so those calcs are pretty right on.

[tlwjkw]

What kinda 'lectric pump? Tha little "universal" is usually not big enough ta support tha motor at high rpm. Just went thru all that for a guy that bought a 200 from me. Good Bosch and regulator and 7500 no problem. Maybe/maybe not.............jmo

[transomstand]

Has he said this is speedometer, or GPS?

[gorillapowered]

I hear yah with the calculations, I dont know whats going on then. All 3 props are all in the seventy's per my Gaffrig speedo which is not GPS and my RPM's I cant get over 6k. I thought I would have more speed with the 29p, but the engine wouldnt spin the RPMs, you could tell it had a harder time spinning that 29 then the 26. I see and speak to some of the guys on here spinning 30p props at 7k. One day I pulled the GPS out of the car to calibrate alittle lol. It was pretty much the same as my speedo, at top speeds my speedo would be 76mph and gps would be 1 or 2 mph below speedo but not much. The fuel pump I didnt put on, it is gold in color with no name on it. If it was not getting the fuel would the engine act funny or stall? or just not go anymore?? The engine acts fine just has no more juice?

[gorillapowered]

how do I check the leakdown??

[tlwjkw]

If it was not getting the fuel would the engine act funny or stall? or just not go anymore?? The engine acts fine just has no more juice?

Not neccessarily. Usually only if its actin' stupid from tha get go. It needs ta be steady enought ta keep up whether its 5 lbs or 60 lbs. You need ta know what tha pressure is at wfo. Like said may or may not be tha problem with your stuff but just something ta consider. There's lotsa things ta look at. Might be tha boat itself! Hard ta say on a computer.................

[gorillapowered]

Ok I think a found A problem, maybe not THE problem. What do u think? I had a break in the reain and found I am running a Purolator #42S Fuel pump. I found it on line it looks like a standered universal fuel pump, talks about vans ect... does'nt say boats and I dont see a regulator. Where would you mount a regulator?? I went from the tank to the engine and didnt see anything that looked like the regulators on line. Do u think this is an issue?? The boat does suck some serious gas though...I thought

[Gorilla0178]

Poss. no regulator if the pump only pumps 6 or so psi. I looked online and the purolator is discontinued, the replacement is a mister gasket mrg 42s. It says it pumps 2-3.5 psi which is real low, and i actually looked at them in the store one tima and think there only rated for like 35gph (after friction loss through the hose its less) which at full throttle is prob not enough. Wildman on here says he use them in place of a primer ball, and didnt recommend using one by itself. I would deffinatly get a actual fuel pump, holly style with a regulator. They pump 100+gph free flow. Hope this helps

[gorillapowered]

cool... I have a primer ball on in now. What should I look at getting?? I see there are alot of options, anyone have good suggest for a set up??

[Gorilla0178]

I got a good deal on a holly style pump on ebay for like 80$ with the regulator and gauge. If not some guys say the holly red doesnt need a regulator, other guys say its better to have one any way. I hope this is your prob, but I would put a real pump on there.

[rhickox]

This is car related, but I had a holley blue which comes w a regulator. It got to where it wouldn't maintain a steady pressure after only a few passes. I also had several people tell me that regulator did the same to them. You could run a Bosch high pressure pump and a aeromotive regulator and a return line back to the tank just like a the 260,280 and drags do.. Just a thought..This would give u plenty of gpm's.This was recommended to me also by a well known engine builder on this site as well.

[gorillapowered]

thanks for all the help I will be busy on my days off.... How exactly do you run a return line back to the tank?? That sound like a good idea

[rhickox]

The instructions on the reg will tell u which is the bypass/return port. It will have 3 ports. An inlet for the high pressure, outlet for the low pressure and the port on the bottom is usually the return... If u go with the high pressure pump u gonna need at least a 3/8 return cause u gonna be bypassing a lot of fuel at low rpms and idle... You just have to find a place on top of the tank for a fitting to attatch the return line to for the bypassed fuel..

[michael_m]

Run a red holly without a reg and you'll be fine that's how my boat is done and it's plenty of fuel for what your turning..

[HStream1]

Obviousely you have a carbed motor. So you need a pump that will maintain 4 to 6 psi constantly. Thats the purpose for a regulator to maintain constant pressure and flow. If your pump produces over 6 psi a regulator is a must regardless.

If you run a HP pump like mentioned by rhickos you definataly need a regulator and the bleed down tee like the 260/280's and Drags. But IMO that is a overkill and not necessary on a carbed engine.

Even with a stock pump in good shape that engine should turn 7k with no problems as long as the rev limiter is removed.

[mrcrsr]

the lil pump won't work, i found that yrs ago on a 150 merc, use a holley red w/ no regulator or holley blue pump(comes w/ regulator) and set it for 6 psi, incidentally, auto zone on us1 carries them by the blvd. as far as the heads, steve(who lives off the blvd) can mill them for you, but you have something else going on

[Gorilla0178]

Who would be steve (who lives off the blvd)? I'm also in the area and might be interested in having them cut a tiny bit.

[mrcrsr]

he does all my machine work as well as gary(instigator), he's more geared towards omc but the merc stuff i know so i just tell him what i need done

[HStream1]

how do I check the leakdown??


You will need a leakdown tester. Good ones sell for as much as $150.00. Harbor freight sells one for around $30.00 that works just ok.

You will also need to be able to find TDC on each cylinder. If you use a TDC indicator and find the crank to rod dwell point a flywheel holder isn't necessary.

[gorillapowered]

Thanks, the local stores and people ae a big help. I know it hard to say over the computer but hat do you think is going on MRCRSR?? have any idea's

[Gorilla0178]

he does all my machine work as well as gary(instigator), he's more geared towards omc but the merc stuff i know so i just tell him what i need done

Any contact info? Or buisness info?

[gorillapowered]

just some information....didnt have much time today to do a new fuel pump, but I pulled the hose off and turned on the old fuel pump and it does work and is pumping I think a lot of fuel, but I guess it might not be enough at WOT.

[gorillapowered]

I also found out that the only mods done to the head are fiberglas reeds and electric fuel pump. At 1 time the engine would spin a 30p chopper at 6400 rpms. The engine did loose RPMs at WOT before the electric fuel pump was put on, it was told that after that pump was put on it was all good.Once upon a time..lol
What are your guys thoughts on porting carbs?? any help w/ RPM and top speed

[gorillapowered]

looking at the holly fuel pumps. Is there any more that my rig will get out of the holly blue, then the holly red besides me paying alittle more money for a blue??

[HStream1]

IMO you are possibly looking in the wrong place (fuel pump) for your problem. While the fuel pump may have issues I believe there is something else going on also. You need to also check the pressure that your fuel pump is delivering (4 to 6 psi). A low pressure/volume fuel pump will produce a lean burn condition if it hasn't already providing your fuel pump is even a issue. Watching gas shoot out of a hose doesn't simulate whats going on when the engine is running. You aren't determining if the fuel pump is actually producing the volume and pressure the engine requires under operating conditions.

Once you determine the pump is producing the required pressure you can eliminate that as a problem.

Like I posted earlier. You can have good compression numbers and still have bad leakdown numbers. A leakdown will better tell you what the internal (mechanical) condition of your engine is before you start getting into wrenching.

If you can determind that the pump is good and the engine is mechanically sound. There is only one other place to go (electrical).

Until you determine things are good or bad by process of elimination you could get cought up in expensive parts replacement and not actually pinpoint the problem(s).

As far as carb porting?? Don't think so.:nonod:

[rhickox]

Get with "Balzy "on here and see if he has any left. He just made a run ofthem but they may all be sold. They are a nice piece and come with instrictions. Only thing else you will need is a air compressor. as Hstream said, this will tell u the true health of the rings/bores.

[HStream1]

I think Mike finally sold all he had made but he can be contacted directly at: [email protected]. he may have enough to make up another one. Or here is the thread link he posted. You can send him a PM also. he only makes the mega balt now.
http://www.screamandfly.com/showthread.php?235307-Get-your-Leakdown-Testers-NOW-!!!!!&highlight=leakdown+testers

[gorillapowered]

Gotcha sounds like a good plan! I am goin to do a Holly Red just cause the pump I have is 2-3psi new so not so good. I am going to do the leak down test, I think I can get my hands on a tester..Then I will try a test run and let ya'll know...thanks:D