90 HP Force 1990

[rrgenter]

I have a 1990 Force 90 HP L drive and I can't get the engine to rev over 2000 in the water, won't get on plane. Seems to idel ok and if you just crack the the throttle open a little she'll run pretty well but, when you open it up to get on plane it goes to around 2000 rpm and won't accelerate any more. Starts a little rough also but allways starts.<br />I have installed a new headgasket,exhaust gasket and water pump.<br />Any help would be gratly appreciated.<br />Ron

 

[eurolarva]

Re: 90 HP Force 1990

You should start with a compression test first then do a spark test. It sounds like the motor is not firing on one or more cylinders. Have you changed props since noticing the decline in power? Do all the spark plug tips look the same or does one or more look clean?

 

[rrgenter]

Re: 90 HP Force 1990

i have a spark tester, but, don't know what to set the gap at due to the plugs flat across.<br />any ideas?<br />thanks

 

[eurolarva]

Re: 90 HP Force 1990

You wont even need the spark plug. Just stick a bolt in the plug boot and try and shoot the spark 1/4 inch to 3/8 inch ( you will however need to leave the spark plug in the cylinder while doing this). The plugs are gapless but should still show carbon deposits or oil build up. What you are looking for is one or more clean plugs. This will typically be the problem cylinder. Compression test should be done on a warm engine. Testers cost about 30 bucks from Sears. Remove all plugs and ground out the plugs while they are hooked to the plug wires. Hit the starter a couple of times while tester is plugged into each cylinder.

 

[rrgenter]

Re: 90 HP Force 1990

Can i do the comp test with a cold engine? It is in storage and would likt to do all I canm prior to end of wintre.<br />thanks

 

[eurolarva]

Re: 90 HP Force 1990

cold compression numbers will not be as accurate however they should be pretty close. If you read 80 in two cylinders and 10 in one chances are that cylinder is bad. Testing the same motor warm might be 110,110,40 which still shows a bad cylinder. The test results you get are still relevent. Someone who can not start a motor with one cylinder at 80 and the other two at near 0 should expect to pay alot to fix that motor or start shopping.