6.2 mercrusier lacking power and won’t run more than 4400 rpms

Coy said:
When I replaced the engine I cleaned the intake out and removed throttle body and cleaned all ports out for iac. Didn’t see any issues. Is there something that I should be looking for that is a known problem? It’s very simple design just a lever and flap
Click to expand...

Does the throttle plate open fully when the throttle at the helm is pushed all the way forward?
 
Espos4 said:
Does the throttle plate open fully when the throttle at the helm is pushed all the way forward?
Click to expand...
So believe it or not when we had the factory scan tool hooked up the starboard motor was reading 87 percent on linear pid and port the one with the issue was reading 90 percent and not exceeding 4400 rpms. So the tech got down in the engine compartment while running and pushed cable all the way and it changed linear reading to 99 percent but didn’t seem to increase in speed.
 
B4DB38C5-0F8F-40E1-AA7B-A88E2ABFAA9D.jpeg
 
Assuming counterrotation is done in the drive, have you tried swapping the ignition modules, pick up sensor or even whole distributor?
The fuel smell thing gives the impression that you have an ignition problem.
 
Both motors have new oem coils and ignition modules. I have installed a brand new cam sensor that is in the distributor. I haven’t swapped the distributor it’s self. I also believe it’s a ignition timing issue not allowing it to give it full power and rpm. I swapped crank sensors between motors last week no change. From my understanding you set base timing with the distributor and then the cam and crank position delegates timing controlled by the pcm.
 
Maybe try swapping the pcm
 
The port engine is a quicksilver reman long block. It has less than 20 hours on it and is doing the exact same thing the old engine was doing to the tee.
 
Coy said:
The port engine is a quicksilver reman long block. It has less than 20 hours on it and is doing the exact same thing the old engine was doing to the tee.
Click to expand...
It has to be something that the computer is seeing that is affecting the power and rpm. I just can’t pinpoint it
 
I'd say start at the beginning, do a compression test.
Quicksilver reman is only as good as the guy building it.
Could be just a coincidence that it's 400 rpm shy like the last motor.
24 degrees total timing is just not enough.
 
I follow you but why does the other motor read the same timing and perform great? It doesn’t always read 24 that’s just at wide open throttle.
 
Never heard of a SBC running less than 30. Anyways that diz is usually a set it and forget it type, maybe not your problem, but seems odd. WOT under load, right?
 
scoflaw said:
Never heard of a SBC running less than 30. Anyways that diz is usually a set it and forget it type, maybe not your problem, but seems odd. WOT under load, right?
Click to expand...
Yes that’s rolling wide open under load. Now during acceleration it’s ranging but once you hit wide open and it stabilizes they both ready 24 btdc
 
Well strange as that is I'd move on. I'd be taking a good look at those plugs and do that compression test. Not unheard of to get a bad part when new, seems to be getting more common. You should be able to do an injector test with tool. Cylinder drop down test.

Someone mentioned a diff. prop for the CR side.
 
Well I just made a phone call to the prop shop and found out that they didnt drop the pitch on the cr prop so that could very well be my problem. Because the props aren’t stock they are 4 blade Michigan props which it would make sense why it would have done this before I bought it because when they swapped the props they never had it setup correctly so I’m gonna pull port prop and run it to the prop shop to pull some pitch out and see if that resolves this issue. I will report back when I get this completed. Thanks everyone for your recommendations!
 
Have you compared engine and exhaust temps during your testing? The engine working harder, should be running hotter.
Comparing gear box temps may also help identify a problem behind the engine.
 
Thornton69 said:
Have you compared engine and exhaust temps during your testing? The engine working harder, should be running hotter.
Comparing gear box temps may also help identify a problem behind the engine.
Click to expand...
These engines in this application run closed cooling systems so the actual engine temps stay the same around 160-165. Haven’t checked the drive to see if it’s getting hotter though. Also could possibly check manifolds them shelves.
 
Coy said:
These engines in this application run closed cooling systems so the actual engine temps stay the same around 160-165. Haven’t checked the drive to see if it’s getting hotter though. Also could possibly check manifolds them shelves.
Click to expand...
I will tell you the engine that runs great does steam more than the port motor that would indicate a hotter exhaust temp.
 
You must log in or register to reply here.

Forum statistics

Threads
113,119
Messages
1,426,564
Members
61,035
Latest member
Lukerney
Back
Top