Force 120 compression problem,help

[rickdevenish1]

Hi I have a force 120 hp 92 model with two cards and 4 cylinders.Compression from top to bottom.125,125,125,90.<br />I am having a hard time trying to start it in the neutral position if I give it some gas it wants to fire and I have got it to run.<br />Any way I just recently got a compression gauge and ran a check.<br />Any info as to what would cause my bottom cylinder to be at 90 and would and does this affect the staring problem that I have.<br />What to do next please.

 

[rickdb1boat]

Re: Force 120 compression problem,help

Decarb and see if that helps. Never know if you have sticking rings in that cylinder. Won't hurt and may help... Force are know to carbon up faster than other models, thereby causing the rings to stick in the piston grooves and let compression to go down, not to mention, blow more oil out the exhaust.

 

[rickdevenish1]

Re: Force 120 compression problem,help

Thanks Rick,now how do I and whats the best and most avalible product to preform the decarb.

 

[seldont]

Re: Force 120 compression problem,help

I use Seafoam. Spray it in the carbs while running until it almost dies. Then shut it down and spray liberally in each spark plug hole and let it sit a few hours(overnight?). Then take your boat out and run it like you stole it. Helped my 95 model 120 to even the compression out and picked up a few pounds in each cylinder as well. I will do again in the spring. You can also use Mercury Powertune I think is what it is called. I think it is a very similar product. Seafoam is also made as a liquid to pour in the gas.

 

[rickdb1boat]

Re: Force 120 compression problem,help

If you have a NAPA auto parts store near you, go in and ask for "Deep Crank", which is made by Seafoam and is the equivalent in spray form. Then use as seldont suggested. Follow the directions on the can as to how long to let it soak. Then Use the Seafoam liquid in your fuel tank every couple of months, to keep things on the insides clean. Let us know what happens...

 

[emckelvy]

Re: Force 120 compression problem,help

I think what you'd be looking for is called "Deep Creep". Here's the Seafoam website for more info:<br /><br /> http://www.seafoamsales.com/deepCreep.htm <br /><br />Cheers.........ed

 

[Oldsaltydog]

Re: Force 120 compression problem,help

Just a stab in the dark by a novice, but are not some models built so that one cylinder has lower pressure than the rest? According to my Clymers manual, that is the case for my Force 90. Of course, my comment does not cover the whole issue. Good luck.

 

[seldont]

Re: Force 120 compression problem,help

Oldsaltydog,<br /> I think you may be partially correct but maybe not in this case. I have heard but I cannot confirm later model 120 horse Force engines ran slightly lower compression in the top cylinder to reduce temps in that particular. Like I said I am not sure about that but my 120 has been about 5 lbs low on the top cylinder since the first time I ever checked it and that was when it was approximately 3 months old. (May just be my motor though.) In this case they are referring to number 4 I think and it should be up with the rest of them. At least within a few lbs, not 35 lbs off.

 

[WhiteHorse]

Re: Force 120 compression problem,help

That is correct. The top cylinder is usually just a hair larger than the other three in order to reduce heat. It definately would not be the other way around. <br />Decarb the motor. Also look at the spark plug from that cylinder. Is it clean or blackened? Could be a blown headgasket... <br />Before throwing up your hands on a blown powerhead, always do the decarb, then pull the head and do a visual on #4. Be sure to replace the headgasket if everything looks kosher.