Engine Rebuild questions 5.7l

[Incredibad]

Its an OMC set up with a GM 350 5.7l. Its time for a rebuild on the motor. I was told to run marine gaskets in the engine and I was wondering how crucial this is as opposed to running normal automotive gaskets, I know about using brass freeze plugs and other marine components when rebuilding but gaskets? Also, Will swapping in an aluminum intake and a better cam help out on the water? WOT is about 3k rpm or so, Id like to be able to give this thing a little more pep

 

[Don S]

Re: Engine Rebuild questions 5.7l

It sounds to me like you are about to go into a rebuild that you probably don't need. You should really find out why you only have 3000 max rpm BEFORE you start a rebuild. It may not help at all.
You need to do a compression test, and a leakdown test first, and if they are ok and your engine isn't knocking, then it's probably fine.
List of possible causes of low WOT (Wide Open Throttle) rpm.

In no particular order

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel
2. Propeller pitch or diameter, damaged blades
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
5. Marine growth on hull and outdrive
6. Wrong gear ratio in outdrive
7. Restricted carburetor air intake (clogged flame arrestor)
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
10. Carburetor defective, or wrong type.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
13. Engine Overheating
14. Engine timing and ignition system operation
15. Remote control cables and linkage for proper travel to open throttle plates fully.

 

[Incredibad]

Re: Engine Rebuild questions 5.7l

Not rebuilding do the the low WOT, rebuild due to extremly excessive oil burning, seems like the rings are worn... also as the motor gets warm, the oil pressure drops to zero and engine speed slowly decreases like the bearings are swelling and slowing down the rotation.

 

[Incredibad]

Re: Engine Rebuild questions 5.7l

Max WOT today was 2k then she developed a low end knock, so its definitely time for a rebuild.

 

[Don S]

Re: Engine Rebuild questions 5.7l

The good thing is, you have to take it apart, and it didn't take it's self apart first. Bet you are loosing a main or rod bearing which will explain the low oil pressure.

 

[Incredibad]

Re: Engine Rebuild questions 5.7l

Thats what my original theory was

 

[Incredibad]

Re: Engine Rebuild questions 5.7l

Now, about the cams, is it really worth it to run a bigger marine cam? as long as there is no valve overlap? or is that not an issue? I know I need to look at a low rpm range, high torque cam. I was looking at this cam, but i'm not sure if the 0 overlap is cutting it to close or what not. I have read a few posts that says putting in a larger marine cam was definitely worth it.

 

[Incredibad]

Re: Engine Rebuild questions 5.7l

no word on cams?