Can't get over 2k on water

[back2mylife]

1988 150 mariner. Rebuilt motor with new gaskets. Didn't pull pistons all "looked" good. Went thru break in procedure. Boat ran great for several trips. Now won't go over 2k rpm on lake. Will on muffs of course. On lake, it does if i go from WOT to idle most times. Rebuilt fuel pump, thought was fuel issue. No help. Spark is good. Compression iffy. 90 on all except 6 and 3 are 70. Will run all day as long as dont give throttle. Does that compression reading match up with my issue? If not, all help will be greatly appreciated.

 

[racerone]

Your motor needs to come apart for an honest / real rebuild !!

 

[back2mylife]

Which means what exactly?

 

[airshot]

When you do a rebuild it needs to be done thoroughly, you cant cut corners like you did. Your compression numbers show you cut corners, time to come apart and do it right this time. Dont nean to offend you, we have all learned the hard way at one time or another

 

[back2mylife]

You not going to offend me. Was my first time trying a rebuild. Any pointers will be appreciated

 

[racerone]

Take it apart.----Pistons on the bench and likely garbage.----Inspect every , nut , bolt and bearing.----Don't forget inspection / reseal of the gearbox.

 

[back2mylife]

Gotcha. How do you tell if piston is shot? Is it pretty noticeable?

 

[racerone]

I think it will be very , very clear once motor is apart.---Good compression would be around 120 PSI.----So 70 PSI tells me a story !!----You said pistons " looked good " , where / how did you look ??

 

[back2mylife]

Just visually what I could see while apart. Felt tight and walls looked good.

 

[Dukedog]

a "recently rebuilt" motor with comp that low is either one of two things.. wasn't done right (block, heads, piston, rings) and/or tha comp gauge is junk.....

one reason for low rpm may be stator.... if it runs and idle's smooth but jus won't turn any more rpm.

 

[Scott Danforth]

Now won't go over 2k rpm on lake........Compression iffy. 90 on all except 6 and 3 are 70.

Your issue is in your post. Compression 90 psi or below is a core motor to be properly rebuilt.

Have the block bored/honed, get new pistons and rings

 

[back2mylife]

Went and bought new gauge. All read between 112 and 117 with it.

 

[Dukedog]

good for you!!! seen it many times.... now check stator if fuel delivery is good..

 

[back2mylife]

good for you!!! seen it many times.... now check stator if fuel delivery is good..

OK to just check resistance with multimeter or do I need DVA?

 

[Dukedog]

sometimes it will show on jus tha resistance but better with a dva....

 

[back2mylife]

I keep finding conflicting info on testing. Can you help point me in right direction? I apologize, just want to make sure doing correctly.

 

[Dukedog]

sorry, can't help with tha 16 amp (your) stuff.. only oem manuals i have left are for tha 40 amp stuff and i sure don't trust my memory in this 'ole noggin' ta try ta explain it and its values you'll be lookin' for.... surely someone on here has all that information and can share it with ya.....

 

[back2mylife]

Lol. Thanks!

 

[Dave1027]

Are you sure you don't have a carb that is not performing under load?
Have you tried having somebody squeeze the primer bulb while it's doing it?

 

[back2mylife]

Yes, tried that. Didn't make a difference.