85hp force compression test ?

[wmmoore]

I am not familar with the process of checking compression on outboard motors. I have a compression gauge and know to take out all spark plugs, my question is do I have to do anything to the carb open or close anything?? or any thing else to get a accurate reading?? any help will be much appreciated..
motor is a 1985 force 85hp model 856X5L. THANKS BILL

 

[roscoe]

Re: 85hp force compression test ?

plugs out, warm engine if possible, throttle wide open.

Welcome to iboats, Happy 4th, and good luck.

 

[john from md]

Re: 85hp force compression test ?

Bill,

When checking compression, you want to make sure that you have the plugs or plug wires shorted out. If you don't, you will damage the CDI units if using the key to turn the starter.

I suggest that you buy or make a starter jumper to put on the solinoid for turning the starter for compression checks. These are sold in Sears and Harbor Freight for @ $25. If you use this instead of the key, you don't have to worry about the plugs being grounded as the CDI's are grounded with the key in the off position.

Again, if you use the key instead of a jumper, you will also have to jumper the neutral start switch as you need to do the test with the trottle in the WOT position. This switch will not allow you to power the starter if the trottle is out of the neutral position.

Regards,

John

 

[wmmoore]

Re: 85hp force compression test ?

John,
Thanks for taking the time to explain this to me I really appreciate it.

 

[wmmoore]

Re: 85hp force compression test ?

Roscoe,
Thanks for the quick reply. how is the fishing down south, I live 80 miles north in Glidden off hwy 13 the walleye fishing has been awesome in the chippewa flowage for the last few weeks..

 

[Spey]

Re: 85hp force compression test ?

Bill,
Thnx for the added comment(s) regarding the use of a starter jumper eliminating potential damages to the CDI ! Way to hit the additional details - nail on the head.