4.3L V-6 Timing Question

[ricky4321]

I recenty bought a 1988 searay with a 4.3L V6 175HP mercrusier. Can anyone tell me where TDC should be at what RPMs. Also can anyone tell me what might cause the engine at only WOT to slightly rev up and down. I can only get 4000 RPMs out of her and that is with a new 19 pitch prop. I did a basic tune-up, but did not check the timing yet and thought I will need to check a few more things. Can anyone give me a list of things to check as well. Thank you in advance.

 

[Boatin Bob]

Re: 4.3L V-6 Timing Question

You don't say how big the boat is, did you run it before the new prop and was it a 19 also? It could be a prop issue if you are running at 4000 a change to a 17 pitch would probably put you around 4300-4400 which is right in the middle of the WOT RPM range.

 

[ricky4321]

Re: 4.3L V-6 Timing Question

We started with a 17 and only got about 4100 RPMs and the same problem happens. With the 19 we now only get 3900-4000 RPMs and it still slightly revs up and down at WOT. Speed is max at 36MPH and the boat is 18.5ft.