Top Speed Help Mercruiser 3.0

[timfives]

All-

i have a mecruiser 3.0. Last season and part of this season the boat would top between 38 and 41 mph. However this season the best i'm getting out of the old girl is 33-35 mph. So i figured some tune up would be in order. I've done the following


It has the dst ignition, which i have changed the cap and rotor along with new plugs.

I've run sea foam through the carburetor to clean out any carbon in the engine, along with adding sea foam in the gas

I've replaced the Carburetor, as the last time i had this one rebuilt I was told it was pitted pretty bad, and an new one would be in order.. I figured now would be a good time.


So after all of this, the boat runs and acts the same.

The boat will cruise at 3800 rpm at 28mph which is about where i cruised with it last year. however 34mph at 4200 revs seems is all its got in it.

The boat has power to bring it up on plane and it just seems that the engine is losing it will to push the old heap.

I have check the compression and all cylinder checked out fine.

Anyone experience a similar situation? I'd love to figure out what to do next..

thanks
Tim

 

[Don S]

Re: Top Speed Help Mercruiser 3.0

Does your 3.0L have a year or serial number? When was the last full tuneup and compression test? How about fuel filters?

 

[timfives]

Re: Top Speed Help Mercruiser 3.0

i believe the engine is post 1991. The boat has been repowered and there is no serial number on the block that i could find. It does have a dst ignition on it if that help.

The compression test and all of the parts i indicated above were complete this past week.

Fuel separator filter was put on at the beginning of the season (April)

I guess what i'm trying to establish is a sound process for trouble shooting.

Next steps?

T

 

[timfives]

Re: Top Speed Help Mercruiser 3.0

Here are some images of the block that have markings on them. Perhaps that will help identify the proper year etc of the motor. any help here would be greatly appreciated.






Thanks guys.

Tim

 

[timfives]

Re: Top Speed Help Mercruiser 3.0

Bump