RPM issue with OMC 225

[run2car]

I have a 1978 Galaxy 1000 BR with a 225 HP Chevy 305 engine. The prop 14 1/2 x 19. The engine is very flat and sluggish and I can't get over 3300 rpm's WOT and only 34 MPH by GPS. It also has a 4bbl carb. If the boat is out of gear it will tach up to about 6400. Any idea's?

 

[Bt Doctur]

Re: RPM issue with OMC 225

Did it ever run properly?
Last full tune up was when?
Throttle plates are wide open?
Wrong gear ratio in the drive?
Compression and leakdown test would be helpful.
And stop running it no-load or your wallet will go empty as fast as the rpm goes up.

 

[run2car]

Re: RPM issue with OMC 225

According to the guy I got the boat from the boat would top out around 50. It has a fresh tune on it. The outdrive is the original, 800 stringer. The throttle plates are opening as they should also but it has had a carb change as it now has a 600 holley on it. I don't know anything else about it. I did run the numbers on the engine and it showed to be a 1976-1979 305. As I said it tach out over 6000 out of gear and starts perfectly and cut off perfectly. Idle speed is right at 900 and purrs like a kitten. I just can't get the thing to turn up while running. Oh, the compression is fine also, checked it this morning.

 

[run2car]

Re: RPM issue with OMC 225

I'm running straight 30 oil. I'll check the fuel pressure and the timing and report back. Should this engine have an HEI distributor? Just curious because it does.

 

[run2car]

Re: RPM issue with OMC 225

May have found the culprit. The cams in the distributor are good and free but the vacuum pot is was frozen. I got it free but it will not hold any vacuum so I think the timing was not advancing. Can't get to to lake today, my tow vehicle dropped a valve when I started it it this morning!!

 

[WizeOne]

Re: RPM issue with OMC 225

Someone stuffed an automotive distributor in your motor. Marine distributors do not have vacumm advances.

That brings up the question, even if the advance works, does the distributor have the proper advance curve and total advance for the motor?

 

[run2car]

Re: RPM issue with OMC 225

Well, I got the vacuum pot changed out so I guess now I will have to get some specs on the vacuum curve for the engine and see how it looks. Is this distributor going to be an issue, if so I will find the right one for it. The vacuum is being pulled from the carb and not the manifold. I know in automotive it should pull at 10 inches of vacuum but in marine applications I don't have a clue.

 

[run2car]

Re: RPM issue with OMC 225

Ok, point taken. So the proper distributor will not have a vacuum advance pot, only the cams(weights). Mine has the cans inside the distributor and the vacuum pot attaches under the cams. Is it possible someone added the vacuum pot? Ans, should the proper distributor be a points style and not HEI?

 

[run2car]

Re: RPM issue with OMC 225

Ok, so if I plug the vacuum port where it pulls from the carb, should I just remove the vacuum pot from the distributor or just plug it off or leave it open? Thanks for all the advice, it really helps me out.

 

[run2car]

Re: RPM issue with OMC 225

Ok, I appreciate the help with this problem. I think I will just buy a new one for and not have to worry about for a while. Thanks again.

 

[run2car]

Re: RPM issue with OMC 225

Thanks for the info. btw, the starter on the boat was automotive but I changed it before putting it in the water as were some of the fuel lines, I don't explosions!