force 120 hp compression test

[nismax]

I just replaced spark plugs got new oil and checked my compression cold engine all plugs removed. Top to bottom 136 141 141 150. What do you think i can post pics of plugs. Engine running great and no problems at all. Thanks

 

[JB]

Re: force 120 hp compression test

All compressed within a 10% window. What is your question? That is great!

 

[nismax]

Re: force 120 hp compression test

Thanks for response. What is manual specs on this engine ? One cylinder is 150 and top one is 136 is ut normal? Thanks again.

 

[roscoe]

Re: force 120 hp compression test

New was around 140-145.
But some model years had different compression on each cylinder, right from the factory..

What you have is about as good as it gets.

 

[H20Rat]

Re: force 120 hp compression test

Don't worry about the numbers. The difference between them is important! Like the other post said, within 10%, good to go. The actual number varies with temperature, altitude, the gauge, and even humidity and barometric pressure.

 

[nismax]

Re: force 120 hp compression test

Thanks guys. Engine was rebuild 2 years ago and its running strong. Just did test before i store it. Hopefully many more season ahead of it.

 

[jerryjerry05]

Re: force 120 hp compression test

You say a 120 what year?Model?Serial#
The early 120's had a comp about 145-155 depending on the gauge.
The later 120's had comp of 145 #1and 4
Then the 2 center was 155.
The difference in the top cylinder would make me wonder.
My twin motors all have 145 on all cylinders.
If I had a difference of 10% I'd freak.
Run it and do a test warm.
Remove all plugs,advance throttle to wide open.
If the results are the same try another gauge.
Then maybe a decarb using Mercury's Powertune. Or OMC's Engine Tuner.
Seafoam doesn't work as good.

 

[nismax]

Re: force 120 hp compression test

Its 96 serial de179390

 

[jerryjerry05]

Re: force 120 hp compression test

Do a decarb.
Carbs set right?

 

[nismax]

Re: force 120 hp compression test

How can i tell? Last time i took carbs a part did go so well. On my jet aki, i am scarrd to take this a part. Shiuld i ? What are the steps and whT to look for? I was going to fog them. Thanks

 

[jerryjerry05]

Re: force 120 hp compression test

These carbs are easy to work on.
Nothing special.Not hard to work on.
Try to turn in the air screw on both carbs and see where they are set.
They should both be about 1 to 1 and 1/2 turns out.Maybe a bit more maybe not.
If your gonna fog? Put Stabil in the gas and go for a ride.
You wanna get it mixed before it's put away for the winter.
Also leave the tank full.

 

[nismax]

Re: force 120 hp compression test

Alright thanks.

 

[JB]

Re: force 120 hp compression test

Old timer's advice: If it ain't broke, don't fix it.