1989 Force 150 Compression Question


New member
I'm the new owner of a Bass Boat with a force 150 outboard on it. The engine is easy to start, runs great and will push the boat about 46mph. I did a compression check to see if all 5 cylinders were equal and they are all within about 5psi of each other. Here is my question: The compression on all the cylinders is between 50 to 55psi. As well as the motor runs, I can't see where the engine could be damaged internally. I read on a few other forums that compression should be between 90 and 110psi, but that was on other makes of outboards. I thought that maybe there was carbon buildup around the rings so I did a decarb on the engine today and nothing really changed as far as compression. After the decarb, I ran it for awhile at about 3/4-throttle to clear it out and again, it ran great. It does idle better after the decarb treatment. I'm not looking for "the engine is junk, get rid of it" or "will make a good anchor". Just wanting to know if Force engines have a lower compression than other brands of engines. Any info would be appreciated.
Sounds like your using a Harbor Freight Tool, ???
HF tools: some are ok, most are junk. A new HF can be defective.
The actual reading should be 145#-165# on all 5 cyl.
The GOOD thing is the comp is close on all 5 cylinders.
Get a different gauge and re-do the test.
You removing all the plugs to do the test?
Unhook the kill switch, remove all the plugs, do the test.
What a difference a gauge makes. All plugs removed. I went to Oreilly's and got their gauge to see what it would show. The low is about 130psi and the high is about 145. The other 3 are about 140.. #5 is the low and will keep an eye on it to see of it changes after running it some.
I have 2 compression gauges and they both were reading the same (50-55psi). Both are going into the trash at this point. Thanks for the replies, I appreciate it.
To bring up the compression: Power Tuner , Engine tuner.
All the big brand motors sell a carbon remover.
Spray it in the plug hole and tilt the motor up tilt the boat down.
Let set for 48 hours.
Start and run, change the plugs after the soak, and keep a set on board.
You can mix the power Tuner in a 1/2 gal. of gas/oil and run through the fuel system.
Make sure you run it out before changing plugs.