alpha one 3.0 won't go faster than 1800 rpm

[wolfman2004]

Hi, I have a 1998 mercruiser 3.0 and tried it out for first time this season. In neutral, I can rev it up, but in gear, it won't go past 1800 rpm. In gear, with the prop removed, I can rev it up. There is some pinging sound. It seems to take more fuel than usual. I cleaned the air filter. The spark plugs are black. The oil level is fine. I would like some input before I bring it to a dealer.<br />Thanks!

 

[jimmmy]

Re: alpha one 3.0 won't go faster than 1800 rpm

I had the same problem with a 3.0 L merc on a 16-1/2 ft Oliver I bought last year. Changed coil, dist cap, points, rotor, condensor, rebuilt carb, drained gas, found cracked head gasket and rebuilt, dropped from 19 pitch prop to 17, two marine mechanics and $1500 later still only brought the RPM marginally from 2400 to 2800. Haven't started her up this year yet but I expect the same. Same prob as you....in neutral revs to 4500 no problem but under load 2800.<br /><br />Let me know if and how you solve your problem.<br />jfielding1@cogeco.ca

 

[cobra 3.0]

Re: alpha one 3.0 won't go faster than 1800 rpm

Does the starter disengage?

 

[sculbert]

Re: alpha one 3.0 won't go faster than 1800 rpm

You might have a exhaust restriction. I would check the exhaust boot after the manifold and make sure it isn't burnt up. or something in the port. Your not putting a load on the engine when your in neutral allowing even poor flow to still rev up.

 

[wolfman2004]

Re: alpha one 3.0 won't go faster than 1800 rpm

Cobra, yes the starter engages. It goes about 15mph max. At home, I took the prop off, put engine in container full of water, engaged in forward gear and it would rev up. I didnt let it go past 4500.

 

[wolfman2004]

Re: alpha one 3.0 won't go faster than 1800 rpm

Mercury Blues, I dont have the manual yet on that engine and I am a newbie on I/O engines. What does the boot look like?

 

[Rickles]

Re: alpha one 3.0 won't go faster than 1800 rpm

whats the timing set at?Did you use the proper timing procedure?fuel pressure?

 

[wolfman2004]

Re: alpha one 3.0 won't go faster than 1800 rpm

Rickles, Havent looked at the timing. Havent touched it either. I finally decided to drop it off at a dealer. I have to wait about a week before he touches it. I will post the fix then.<br />Thank you all!

 

[cobra 3.0]

Re: alpha one 3.0 won't go faster than 1800 rpm

...that's disengage! Do you hear a whirring sound? Starters sometimes engage and do not disengage once the motor is running.

 

[wolfman2004]

Re: alpha one 3.0 won't go faster than 1800 rpm

Cobra, Sorry, misread your message. I don't know if it desengages. I remember more of a pinging sound and the motor vibrating at 1800 rpm. I dropped the boat at a dealer. I will let you know what happens.

 

[wolfman2004]

Re: alpha one 3.0 won't go faster than 1800 rpm

Well, I got the boat back from the dealer. They changed the spark plugs only. It was running on 2 cylinders instead of 4. Now it's running better than ever. Funny thing though. It used to go up to 4800 WOT. Now I got it to go to 5600 rpm. Before I brought it to the dealer, I suspected the gas and put octane booster. I wonder if it's the octane booster bringing the rpm up?

 

[Fishermark]

Re: alpha one 3.0 won't go faster than 1800 rpm

I doubt the octane booster had anything to do with the RPM increase. You mentioned you changed pitch on the prop by two inches -- that will give you about 400 RPM, plus the fact that the engine is running better. More power equals more RPMs. I would definately suggest going back to the 19 inch prop.

 

[wolfman2004]

Re: alpha one 3.0 won't go faster than 1800 rpm

Fishermark, I never changed the pitch of the prop. It's the original prop on it. You read the post from Jimmmy. Should I be concerned about the increased rpm?

 

[Fishermark]

Re: alpha one 3.0 won't go faster than 1800 rpm

Sorry about that - you're right - I looked at someone else's post. I'm not sure of the upper RPM range for that engine, but I'm sure it is supposed to be less than 5600. Probably about the 4800 that it used to be. Generally speaking, like I mentioned earlier, one inch equals about 200 RPM.

 

[Invader92]

Re: alpha one 3.0 won't go faster than 1800 rpm

Was going through this post cause I am having issues with my 3.0. I was running my boat Sat the 11th of Sept and refueled at a shoredock and all of a sudden I lost 1200 RPM's. At about 1500 RPM's it would rev to 1700 then drop back to 1500. At WOT it wouldn't get over 3800 RPM's. I'm going to do more research on it but I wanted to also say hey to Fishmark. I'm from Port Charlotte. I bet we might know some of the same people.