Toolman62

I took it out Saturday and ran it with a fuel pressure gauge on it. 3800 RPM's WOT and fuel pressure stayed at 41 psi throughout entire throttle range. Engine is coming out Friday so I can find what the problem is.

kidturbo

If my guess is correct and that's a 1.26 ratio drive, there isn't an engine problem, your just running out of torque / cam.

After reading this again, I'm thinking air flow restriction somewhere. Or someone has had their fingers in the PCM and changed something like timing or fuel curve that's holding it back.

Trash

It is HIGHLY unlikely it came with a 1.26 drive. HIGHLY unlikely.

kidturbo

I would certainly agree, defiantly not 1.26 from the factory on that boat. But if all the information he provide about the prop pitch, top speed, and max rpm is correct, at 13% prop slip it equals a 1.26:1 ratio drive.

I'm thinking someone changed the drive, cause as Griff posted "Its impossible to run 57mph at 3800rpms with a 23"prop and 1.5 ratio drive."

I'd verify that what ratio is before pulling the engine. Pretty simple, put it in gear, mark the prop and engine dampener starting position with chalk, have someone rotate the crankshaft until the prop makes one complete revolution, see where the crankshaft marks fall. If it's a 1.5 ratio the mark should be exactly opposite from where you started. Or 1 and 1/2 turns on the crank equals 1 turn of the prop. 1-1/4 = 1.26 , 1-3/4 = 1.75 and so on...

I'm possibly wrong, but I run a 1.26 ratio, and plugged his info in a prop slip calculator, which shows slip to be 13% if he has that drive. More likely than having 3% prop slip as would be the case with a 1.5 ratio...

Griff

If he had a 1.26 ratio drive, he still would have picked some rpm going from his 23" prop to the 21" that he tried. He said it still ran 3800rpms.

Griff

Have you verified the igniton timing in base timing mode and veriified that the timning is advancing properly????

kidturbo

Guess I missed where he changed props. Your correct, would expect some change no matter what drive then. I just don't feel it's "internal" unless it jumped a tooth on the cam gear or something crazy like that.

Almost like there is a rev limiter on it. I'd verify every setting, sensor, throttle body movement, and anything else you can check before pulling the engine. Without seeing it in person, can't imagine what we are missing.

Randy Nielsen

iTrader: (4)

[ATTACH=CONFIG]511963[/ATTACH][ATTACH=CONFIG]511964[/ATTACH]Have you checked the timing in base timing mode? It is easy to do without a scanner just jump the A and B terminals on the diagnostic connector & set timing to specs normally. My 1999 H2X with a 385hp 454mag MPI took quite a bit to get on plane in stock form with a 23p Mirage+ & would do 68mph @ 4900 rpm with a 1.5 ratio bravo 1. If everything else has been checked that is where I would go just to physically verify it is right. If you don't jump the terminals it will run but won't have any power under load. (ask me how I know). Randy

Toolman62

Thanks Randy, I'll jump the terminals and ck the timing in the morning. I was pulling it in to my shop and pulling the engine in the morning so I'll ck that before I do anything else. If the timing is different then I'll go test run it again.

Toolman62

I just checked the timing as Randy suggested. Everything was right on...8 deg BTDC at idle (600 rpm), 20 deg @ 1500 rpm, 24 deg @ 2000 rpm. I feel like something is going on inside to cause power loss. I feel like it's running out of HP under a load. I used the trailer switch last time out and ran the prop pretty high, tach went to 4100 rpm's. I think for me to know what is going on I'm going to pull the engine. Worst thing if nothing is wrong, a gasket set to put it back. It comes out tomorrow!!