Rebuilding 140HP 3.0

[myoung84]

I have an '85 boat with a 140 horse 3.0L. The boat sat for a few years before I got it and the previous owners put it on the water and supposedly overheated it. I aquired this boat at the end of last summer for free and have already put a floor in it since the old one was rotting and it has sat all winter.

Now, I did a compression test and the middle two cylinders were very low. I would have to assume that either the valves are sticking or the rings are not sealing up. I think I have decided to give this engine a minor overhaul, maybe striping down the block, having it cleaned and the cylinders honed and replace the rings and gaskets. What all is involved with this and where is a good place to get parts? I have worked on a lot of car engines but never fully rebuilt one. Does anyone have any other suggestions to help me along?

 

[cheburashka]

Re: Rebuilding 140HP 3.0

Maybe it's just me, but I'd recommend running it as-is a bit. Put some sort of penetrating oil into the cylinders and maybe Seafoam the intake to make sure that the reading you're getting isn't due to stuck rings, surface rust in the cylinders, or carbon buildup in the valves. If it hasn't run in years, I wouldn't expect it to show its true compression unless it's been properly brought back into service. You may just be throwing away your time and money. Maybe pull the head to see what's up there, but don't dive into the block unless you're sure that's what's needed.

Do you know how many hours are on it?

 

[fishrdan]

Re: Rebuilding 140HP 3.0

What were the compression numbers? Did you run a wet compression test also? Could be a bad head gasket since you said 2 adjacent cylinders are low.

 

[Don S]

Re: Rebuilding 140HP 3.0

You can not do a compression test on an engine that has been setting for years and expect the test to mean anything.
Start it up, run it for a while, wear off any surface rust and pump up the lifters and get those open valve seats cleaned off a little.
Then do the compression test. Even the next day is ok, but not after setting for years.
The link below explains how to do a compression test that means something.
http://www.boatfix.com/merc/Bullet/97/97_25.pdf

 

[Bondo]

Re: Rebuilding 140HP 3.0

What all is involved with this

Ayuh,...

I agree with everybody,... Run it on the muffs for a 1/2hr,..
Then run the Tests,...

Up in the Adults Only section at the top of the forum, you'll find factory manuals,+ a host of other important Knowledge.....

 

[chiefalen]

Re: Rebuilding 140HP 3.0

May i ask a few questions??

1- What make is the motor and drive ?

2- What else did you do before you did a compression test? Example- Changed the motor oil and filter, changed the t-stat, pulled the valve cover and bothered to look at the valves ?

3- What was the numbers from the first test ?

4- Did you put water to the drive when running the motor, and did it get hot ?

5- You didn't run the motor at all ?

 

[myoung84]

Re: Rebuilding 140HP 3.0

The compression test was done last year so I don't remember the numbers. The engine has been run. It was running hot and we finally figured out that the engine drive coupler was bad and the outdrive was not turning, so of course the impeller was not turning. We fixed that and have run the engine on muffs as well as running it on the lake for about 10 minutes. The compression test was done after all that since when I has running it on the lake with a load on the engine, it was making a weird sound, which turned out to be an engine running on 2 cylinders. I have not pulled the valve covers but plan to soon, the boat is not at my house right now.

Just trying to pool ideas together before I pull the boat to my house to start tearing into it. I wont be able to do much to it until after April, since I am getting married then. I hope to start working on it the first of May and have it back on the water ASAP. I don't want to rebuild the engine at all unless I absolutely have to.

 

[myoung84]

Re: Rebuilding 140HP 3.0

Bump

 

[chiefalen]

Re: Rebuilding 140HP 3.0

Impeller is toast and i bet the water tube is melted, and if it were my boat i would pull the riser, and check to see if it was plugged up and for the flapper to be still there or wedged in the exhaust tube.