85HP 1989 400 RPM

[jippie98]

I am stumped....... I have completed the following repair/replacments and still cannot get over 4000 RPM?<br />Waterpump/impeller<br />Fuel pump<br />carbs cleaned and sync<br />Compresion is 125,125,130<br />spark on all cyl<br />15 pitch prop<br /><br />Could it be the Tach? I have a 18ft Mirrorcraft CC and at 4000rpm I was going 34mph? Does that sound right? Engine runs great and revs smoothly without and problems......<br />What is my next step? You guys have been very helpful in the past...Thanks

 

[Realgun]

Re: 85HP 1989 400 RPM

Do you know that the Force is a 20 pole alternator and you need a 20 pole tach?

 

[jippie98]

Re: 85HP 1989 400 RPM

It is the original tach that came with the boat when I purchased it. Never had any reason to doubt that it wanst original.

 

[eurolarva]

Re: 85HP 1989 400 RPM

The 34 mph is that off GPS or off a speedometer? IF the tach is off the speedometer is probably also wrong. Then again an 18 foot boat loaded with an 85 HP I doubt you will get much more speed out of it. IF tach is correct maybe a different pitched prop will increase RPM.

 

[jippie98]

Re: 85HP 1989 400 RPM

I was using Eagle 480df for speed..... The prop is already a 15 pitch....13pitch? have never seen one for this engine....

 

[Realgun]

Re: 85HP 1989 400 RPM

More than likely the tach is off somwhere. 34mph is about where you should be.