87 15 HP Evinrude - 50 psi on both cylinders - runs great

[Hezekiah]

Hi guys:

Just checked my compression on my motor and it's registering 50 psi on both cylinders. The motor runs great...very strong.

I cleaned the carbs a couple of weeks ago...could I have slightly messed up the timing and it's effecting the compression test?

Thanks.

 

[ondarvr]

Timing has no affect on compression.

There are several reasons it could be read that low.

1. Using a pull rope to get a compression reading typically leads to a lower number because it's harder spin it quickly.

2. Gauges are known to get very different readings, and the difference can be sizable.

3. Method used, different people can get different numbers on the same motor.

5. Maybe it is that low, but still runs OK.

 

[Hezekiah]

Ok, it is a gauge from Harbor Freight...so maybe it's a lower quality piece of equipment.

Also, it is a pull start...boggles my mind. Such a great running motor, never thought it would read that low

I appreciate the response.

 

[Hezekiah]

Only problem I think I might have is when i try to sell it - nobody is going to want a motor with compression that low.

 

[ondarvr]

You still don't it's that low, and most people won't check the compression.

 

[boobie]

Do a GOOD decarb on it and then recheck the compression on it.

 

[Hezekiah]

Do a GOOD decarb on it and then recheck the compression on it.

Have that on the agenda for tomorrow - just talked to my motor guy and he said the same thing.

 

[JoshKeller84]

before you try anything else, since youre using the HF gauge, try a different attatchment than the screw in plug. Use the press in one, and I bet your compression will come up significantly. the hose they use on the screw in plug is not large enough diameter to allow ample air flow - the push fit adapters are larger.

 

[Hezekiah]

Ok, thanks for that - I will try to locate the piece you're talking about. You think an auto parts store should have it? Or dare I get one from HF?

 

[JoshKeller84]

did you get the compression testing kit from HF? this one?

http://www.harborfreight.com/compression-test-kit-8-pc-69885.html

 

[Hezekiah]

No sir, it was this one

http://m.harborfreight.com/quick-connect-compression-tester-95187.html

 

[JoshKeller84]

read the reviews - go to the negative ones. lots of them are reading way low - as is the one I have. Its a design flaw in the hose connecting system.

 

[Hezekiah]

Yeah...you're right. I'm reading them too...makes sense. There is a lot of hose to travel.

 

[Hezekiah]

There are so many bad reviews...I might as well junk this thing....now convinced it's the compression tester.

 

[AlTn]

if the large brass quick connect fitting will unscrew from the gauge hose, will the threaded portion now fit the spark plug hole?..if so...try fitting it with an oring and retesting...both spark plugs removed and pull until the gauge indicates its highest pressure < needle quits rising >

 

[Hezekiah]

if the large brass quick connect fitting will unscrew from the gauge hose, will the threaded portion now fit the spark plug hole?..if so...try fitting it with an oring and retesting...both spark plugs removed and pull until the gauge indicates its highest pressure < needle quits rising >

I was looking at it this morning before I went to work to determine the same thing. To me it looked like different connections - but I will look at closer after work.

 

[Bullie]

I went through 3 of the HF compression gauges before I gave up and bought one from Auto Zone. It doesn't look as cool or have as nice a carry case as the HF gauge but it works. I could never get the HF gauge to get above 60lbs on any engine.

 

[Hezekiah]

I went through 3 of the HF compression gauges before I gave up and bought one from Auto Zone. It doesn't look as cool or have as nice a carry case as the HF gauge but it works. I could never get the HF gauge to get above 60lbs on any engine.

Yeah...most stuff from HF I can work with...this I could not...I should have read the reviews online first...

 

[Bullie]

Wish I had. I have some decent tools from there but some of it is just junk. I think you will be pleasantly surprised as to how much compression your motor is actually producing.

 

[Hezekiah]

Wish I had. I have some decent tools from there but some of it is just junk. I think you will be pleasantly surprised as to how much compression your motor is actually producing.

Yeah, I expect it to be over 50 PSI...that's for sure