Force 50 compression difference

[reelfishin]

More than 10% difference in compression in any cylinder would indicate a problem to me. It could be carbon but chances are with an older motor like that your looking at bigger problems.

(Not sure how this happened but my reply is showing up as the first post here)?

 

[blueoval78]

Force 50 compression difference

Hello, I have had several posts on here concerning speed and running issues out of my '88 Bayliner Capri 1500 with Force 50. Today was my winterizing day so I figured I would do a little bit of testing before putting the boat away. After running a compression test; my top cylinder yielded 120 psi and my bottom 100. Is this acceptable? Could my motor be carbonned up? Could this cause my top speed to be 3mph slower than factory specs?

 

[jerryjerry05]

Re: Force 50 compression difference

It could be carbon or it could be a bad head gasket.What guage?Screw in type?Push in type?Push ins give terrible readings.
Squirt some oil in the cylinder and see if it improves.If it does then do a decarb.No change then spend the $ and check the head gasket.A very small hole can allow the motor to run but have low comp.
Have a good winter.I moved from Mi.Now I don't have to winterize.63` this morning.BRRR!!! J

 

[blueoval78]

Re: Force 50 compression difference

I used a screw in type gauge.

I bought this boat dirt cheap in May knowing that it had performance issues. Earlier this year I rebuilt and cleaned the fuel pump and carburator. This improved my top speed from 10mph to 25mph. According to factory specs I should be at 29mph so I figured there might be something else; which is why I checked compression. The boat starts and runs fine; it just seems to be doggy.

One note, both plugs get black, wet looking pretty quick; with the one in the 100psi cylinder being worst than the other. What does this mean?