1988 135hp merc ob problems

[Donny Mize]

Hello all,
First time post here so any help is appreciated!
I have a 1988 searay with a 135hp ob on it. I do not know how many hours it has on it. It seems to run a bit loose, kind of like a 20 year old motor.
My problem is when at speed it looses rpms and speed. I have checked to compression and have 75psi in each cylinder when its cold, which I have read to be normal. I have good fuel flow to carbs and fuel is good.
What i just noticed is a burnt connection on my rectifier.
So my question is would this cause my problem?
Or am i looking at a doing a rebuild?

 

[j_martin]

Re: 1988 135hp merc ob problems

75 lbs compression sounds waaaay low. Are you sure your gauge is right?

Any fuel restriction will cause it to die back at WOT. It can also lean it out and cause pistons to overheat and self destruct.

Check fuel filter, pickup screen, hose and bulb, (most aftermarket are not adequate) fuel pump.

Burned connections on the rectifier happen all the time. Not good, but shouldn't cause the engine to misbehave. Check the rectifier.

Do you have a tach and does it work?


hope it helps
John

 

[Donny Mize]

Re: 1988 135hp merc ob problems

The 75lbs sounds low to me too but was explained to me due to the engine sitting for a couple weeks. I am going to run it this weekend and see how the pressure looks then. I have no reason to doubt the gauge but there was no wrench flat to tighten the hose so it does seem possible to be leaking. I beleive the compression to be ok I was worried about a blown piston and did not see any indication of that.

I am also replacing the fuel line, which has kinked on me more then once, it just seems old and in need of replacing. I also check the other fuel items whiel doing that, but how do i check the fuel pump?

I am also replacing the rectifier.

My tach has been spotty at best, there are some electrical issues with the gauges I am still trying to straighten out (the hackanic before me sucked)