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1993 force 70hp low compression and piston damage

Dan804

New member
Hello everyone, recently I was having issues keeping my boat running at idle when dropped in the water. I was adviced to replace head gaskets as original compression test was 100, 70, and 50. I have a 2 stroke single carb force 70hp. It runs and sounds fine on the hose and it went for a decent run on the water until we stopped and idled and then wouldnt start back up. I replaced my head gasket, upon replacement i noticed leaking into cylinder 2 and cylinder 1 has low compression. Cylinder 2 has a little damage on the piston. After replacing the head gasket my compression test improved to 90, 90, and still a 50psi on cylinder 1. Do you think the picture displayed for the damage in piston 2 is causing the low comp in cylinder 1? I will take her on the water tomorrow to test and see if she can hold a whole days worth of boating. Atleast compression improved.

Would you recommend doing an engine rebuild if you think the piston 2 is the cause? Thoughts? Ideas? Thank you so much in advance

2yulr3a.jpg

2poz255.jpg
 
I have a 1995 70 HP Force, and it runs great...now. I know this day is coming for me too. But until it does, I'm sticking with her. When that day comes, I will re-power, not rebuild.
 
The damage is only gonna get worse!!!
The compression should be about 145# on each cyl.
Get another gauge.
The cyl.walls don't look too bad(more pics) but if not taken care of you can destroy the block along with the pistons.

The rebuild isn't hard "yet $$" once the damage is done it gets harder$$, getting the blocked bored out and buying new parts.

A rebuild could be $800=1200 depending on how bad it gets.
Some charge 2-3X that .
Bring it on by I'll do the job. Add a location to your posts.

The 3cyl. with 1 carb wasn't a great idea.
If you get it rebuilt use extra oil and use a premium oil like Amsoil
 
I like to try and determine why the problem occured. It looks to me like the center piston was carbon fouled more than the other two. Definately pull it apart and deglaze the cylinder walls and measure them for proper bore and out of round. It is possible the primer was leaking allowing raw fuel to get sucked into the center cylinder causing it to load up with oil is the only thing I can think of. Adapt your primer bulb from the tank to the primer solenoid and see if it leaks when you put pressure into the input. A bad float valve is another possibility giving you a over rich condition. If the crank and connecting rod bearings are in good condition put in new rings and run it till it pukes. Rebuild the carb, fuel pump and primer and replace all the fuel lines!
 
That damage can be caused by a number of things.------------Wrong prop.---------No maintenance to water pump.---------Poor quality oil.-----------Wrong mixture.----------Plugged carburetor.-------------------Motor must be torn apart for inspection !!
 
The damage is only gonna get worse!!!
The compression should be about 145# on each cyl.
Get another gauge.
The cyl.walls don't look too bad(more pics) but if not taken care of you can destroy the block along with the pistons.

The rebuild isn't hard "yet $$" once the damage is done it gets harder$$, getting the blocked bored out and buying new parts.

A rebuild could be $800=1200 depending on how bad it gets.
Some charge 2-3X that .
Bring it on by I'll do the job. Add a location to your posts.

The 3cyl. with 1 carb wasn't a great idea.
If you get it rebuilt use extra oil and use a premium oil like Amsoil

Id love to but im in virginia haha and thank you for the info. I think I should just go straight into getting it rebuilt
 
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