Compression tester question ?

[Gulf Boater]

Need to pick up a compression tester to test my 125. Do I need a special kind due to the surface area plugs. I have read that most people use automotive testers but want to make sure I'm not going to damage the top of the piston

 

[pnwboat]

Re: Compression tester question ?

No special compression tester required. Any standard compression tester will work. The adapters that screw into the spark plug holes only have about a half inch of threads so they don't stick out far enough to come close to the piston.

 

[Gulf Boater]

Re: Compression tester question ?

Thanks off to Harbour freight

PS

Do you know what size the thread is for 125 force want to make sure it comes with rt adapter

Found it 14mm thread

 

[jerryjerry05]

Re: Compression tester question ?

Any tester should work.
Just make sure that you remove all the plugs to do the test.
Then ground out the plug wires or leads.
Some say just unhook the kill switch.Sometimes that works.Sometimes it doesn't.

 

[Scott Danforth]

Re: Compression tester question ?

Thanks off to Harbour freight

PS

Do you know what size the thread is for 125 force want to make sure it comes with rt adapter

Found it 14mm thread

I would get something higher quality than Harbor Freight.

 

[Gulf Boater]

Re: Compression tester question ?

Wasn't really looking to drop $100 + on a tester I will only use a couple times.
However marinas test was 150,30,80,25
My readings were 130,129,130,130

So now I don't know what to think

 

[pnwboat]

Re: Compression tester question ?

Some of the auto parts store will loan you specialty tools for a small refundable deposit. I believe AutoZone will do this. Might check them out.

 

[carholme]

Re: Compression tester question ?

I wouldn't worry about the tester you got at Harbour Freight. If you want to test it yourself, hook it up to an air compressor or a spare tire after checking the tire pressure. Then just use the compression tester as a tire gauge and see what it reads in comparison to the known pressure in the tire. Telling some marinas to do a compression test on your engine is like opening your wallet and letting them take what they want.

Gerry

 

[auchandler1]

Re: Compression tester question ?

I bought mine at autozone for like $10 and it works great.

 

[sphelps]

Re: Compression tester question ?

Any tester should work.
Just make sure that you remove all the plugs to do the test.
Then ground out the plug wires or leads.
Some say just unhook the kill switch.Sometimes that works.Sometimes it doesn't.

I got a H/F one on sale. Took plugs out , left wires loose , did test , 119,118,119. Did I do that wrong? Not sure about grounding out plugs?

 

[Gulf Boater]

Re: Compression tester question ?

Then ground out the plug wires or leads.
Some say just unhook the kill switch.Sometimes that works.Sometimes it doesn't.

How does one go about grounding the wires ? Also where is the kill switch located on force 120 ?

 

[jerryjerry05]

Re: Compression tester question ?

I use a #10 wire in a 3-4 wire (I call it my little squid)grounding harness.
I use a #4 copper connector,3/4 pieces of #10 wire about 15" long.
Strip all three about an inch and install in the #4 connector.
Strip about 3/4inch from the other end and solder them so the end becomes hard.
There you have a grounding lug for either a 3 or 4 cylinder.
My twins are 3 cyl so that's all I need.

Compression results: A cheap tester is all you need.
The results are what you need.
All cylinders should read the same.Your tester might read different than mine.
Mine might read 150 when yours reads 125 But if all 3 or 4 read the same that means the cylinders are ok.
Your looking for the same readings across all cylinders. One show different thats what your looking for.