3.0 Mercruiser wont get above 3000 rpms?

[Jordanngfd326]

I recently purchased a 1988 Glasstream 172 Cutlass with a Mercruiser 3.0. This is my first boat and i am not mechanically inclined. The boat cranks fine, runs fine, planes out fine, but i can not get over 3000 rpms. Any suggestions?

 

[Bondo]

Re: 3.0 Mercruiser wont get above 3000 rpms?

This is my first boat and i am not mechanically inclined.
Any suggestions?

Ayuh,... Welcome Aboard,...

Find yerself a boat Mechanic,..??
Tune up,..??
Compression Test,..??
Filters,..??
Carb tune,..??
To big a prop,..??

 

[Jordanngfd326]

Re: 3.0 Mercruiser wont get above 3000 rpms?

I just replaced the carb, checked the fuel filters, and checked timing...boat still maxes out at 3000rpm... The previous owner said he put a bigger prop on in for more power, i believe it is a 19p...thinking i should drop to a 17p. Any thoughts??

 

[fishrdan]

Re: 3.0 Mercruiser wont get above 3000 rpms?

The previous owner said he put a bigger prop on in for more power, i believe it is a 19p...thinking i should drop to a 17p.

A 19P prop sounds about right. I would verify the prop pitch though, since the PO said he put on a BIGGER prop, maybe he stuck a 23P on there You need to gain 1500RPM so going with a 17P prop won't help much, if a 19P is on there. Sounds like an engine problem to me. I'd look at the ignition, see if the timing is advancing all the way, distributor weights free and snap back. Actually, you probably need to do a full tune-up, plugs, wires, cap, rotor, points, filters, if it hasn't been done all ready.

 

[ckwizard]

Re: 3.0 Mercruiser wont get above 3000 rpms?

Start with the obvious, put your shifter in the full forward wide open throttle position and then go look down the carb to verify that the plate is full open and not just partialy open.

 

[Jordanngfd326]

Re: 3.0 Mercruiser wont get above 3000 rpms?

Will check to make sure it is fully open on saturday...also going to clean the spark arrestor which looks to be a bit dirty and changing the spark plugs. Should be on the water sunday to check it out.

 

[djrilo]

Re: 3.0 Mercruiser wont get above 3000 rpms?

Check the ratio of the out dive..should be 1.98....I bought a 91Sunray E-170 w/ a 3.0 merc I/O ....Ran great.. but would'nt get over 2200 RPM...after spending $2800.00....with no fix.... I looked at the alpha one....it was a 1.50 ratio for a V-8..... went to a marine shop traded even up for mine....and bam 4500 rpm....and wow what a different boat......

 

[farmboss]

Re: 3.0 Mercruiser wont get above 3000 rpms?

had the same damn problem.... check to see if the weights in the mechanical advance are working... mine were rusted stuck.... mine would go ton 3800 ,,,, i cleaned the distributor all up and now she
ll do 5000