no compression in 1 cylinder

I have a 1998 Force 120 with 150 compression in bottom 3 cylinders. The top cylinder is only 30!!! What does this mean? And what can I do to fix it?

Re: no compression in 1 cylinder

hello<br /> means its time to pull the cylinder head to see if you smoked a piston or blew a head gasket. then it will be time to find out why it failed. good luck and post back what ya see in the head/cylinder

Re: no compression in 1 cylinder

Ok, I pulled the head cover off and I found that the cyclinder wall of the cylinder that had low compression was scratched and scuffed, obviously due to the piston brushing against it.<br /><br />Sooo, what could have caused this? What needs to be done from this point? I would imagine the cylinder wall (is that called the head?) needs to be fixed, but how?

Re: no compression in 1 cylinder

I am somewhat of a novice but like to do my own repairs. According to your previous post you had just fueled before your trouble started. It sounds to me as though you either did not have enough oil in the gas or maybe had a healthy shot of water in the gas you bought. Oil would be my first guess. It also could have overheated. At any rate the powerhead will need to be pulled off and torn down for a complete inspection and if the scoring of the cylinder is a severe as you describe you will probably need to bore that cylinder oversize or have it sleeved and replace at least the number one piston. I do not know haw mechanically inclined you are but this can be done by most anyone with a good deal of mechanical aptitude and patience as well as a decent set of tools. I did my old Chrysler 100 HP several years ago and it was not really that hard at all. If you go this route make sure to replace the water pump impeller and at least inspect and test the thermostat so if it was heat related you do not damage your rebuilt engine.

Re: no compression in 1 cylinder

hello again<br /> no that is the cylinder wall. it is now time for an honest self eval of your mechanical skills. you now need what is called a rebuild. this will entail removing the motor from the hull. a complete tear down and inspection. you should also rebuild the carbs and fuel pump. do the water pump t-stats and relief valves as applicable. it is not super hard but does require a few special tools. mostly it will require meticulous attention to details and a lot of patience. good luck and keep posting

Re: no compression in 1 cylinder

Well... that sucks! But I think I am up to it. I once pulled an engine out of a subaru XT and put another one in and it worked fine. All I referred to was a Chiltons book. Oh, and I also write software fulltime so I am pretty good with detail! The only thing that is going to be a pain is acquiring the tools! I hate to go buy tools just for this one job...<br /><br />And I have 2 theories as to why this happened...<br /><br />1.) when I got gas, I was EXTREMELY low... I shot 12 straight gallons into a nearly empty tank followed by 1qt. of oil. Within minutes I was out of the wake zone and full throttle on a VERY calm day. I have suspicions that I was using straight gas when the breakdown occured.<br /><br />2.) through research I have learned that the fuel lines to the cylinders can get clogged causing a temporary application of fuel/oil.<br /><br />I know my water was circulating so that rules that out. What do you guys think?

Re: no compression in 1 cylinder

In the future I would add a little oil then a little gas at a time so to mix it better. If it is where you can it is always good to mix in a seperate container then add to your tank. I very seldom do that myself. Aside from a good set of wrences and sockets you will need a torque wrench and a puller to remove the flywheel. With patience you can get by without a piston ring compressor. I did anyway. Get a good shop manual. Make sure you clean everything very well and lube propeerly while assembling. Be careful when installing the piston/rod assembly in the block because the edges of the crankshaft are pretty sharp and one nick in the rod bearing surface and you will need a new rod. (I made that mistake) Have a reputable shop do your machine work. I also suggest taking pictures during disassembly to refer to when putting every thing back together. (wiring and such) Good luck and let us know how it goes......

Re: no compression in 1 cylinder

Ok thanks... I heard that I should be able to hone the cylinder and replace the piston with the power head still mounted on the boat. Is this possible. I sure hope so... would save a lot of trouble and time...

Re: no compression in 1 cylinder

You would first remove the carbs, then the reed block assemblies (Intake). Behind them is the connecting rod caps.<br /><br />Either 1/4 in or 5/16 in 12 point socket is required.<br /><br />Pop the caps off and out comes the piston though the back of the engine.<br />You may have some loose needle brg's to collect. A small magnet will grab these for you.<br /><br />Upon reassembling, grease the needle brg's so they stay in place and bolt the cap back on.<br /><br />Its that easy.<br /><br />TMD