pressure test

[flattop1]

Is it possible to pressure test the crank case assembly?
I have replaced my check valves, rebuilt carbs, tested compression, timing and link and sync Still have an eratic idle seems to hunt a bit to much andthen die off.
Would a bad lower crank seal cause this?
Thanks for any help.
1985 90 hp evinrude

 

[boobie]

Yes.......

 

[Bosunsmate]

look at your spark plug colours, any different?

 

[emdsapmgr]

How does the compression on the bottom cylinder compare to the other three?

 

[flattop1]

checked plugs both bottom plugs are a bit dirty vs top 2 which look good.
currently on the lake so no gauge., with me.
How do you plug exhaust for pressure test? removing engine from lower unit to make a block off plate seems counter productive.

 

[flattop1]

Went to Ql78 plugs color cleaned up compression is 123-129 with bottom cylinder being 126.
engine died when loading on to trailer and when i removed the plugs they seem to be wet.
Maybe the float is set a bit high.
How would I do a pressure test?
Thanks Tony

 

[Ibl0wstuffup]

Did you check compression with the engine warm? I had a v4 that passed cold but dropped to 70psi in one cylinder warm. It had a scratched cylinder.

 

[racerone]

??-----There are 4 seperate crankcases to pressure test.-----You can use the bypass covers to find compression in them.-----No need to blank off the exhaust.-----So a bypass cover can be adapted with a gauge and pull the motor over to compare pressures.---Test one at a time.

 

[flattop1]

checked compression cold. will re test .
I overlooked the fact all the cylinders were separated by the sealing rings . interesting ,what pressure would it show 3-4lbs?
What would be a test for the lower crank seal? manual has no indication of any test procedure.

 

[racerone]

???---Crankcase compression test on # 4 cylinder will also test the bottom seal.----Removing the bypass covers will allow you to inspect pistons / rings.--I recommend you do that.

 

[flattop1]

10-4 runs great once rpms are up above 1200 rpm

 

[Bosunsmate]

10-4 runs great once rpms are up above 1200 rpm

Might be the reeds

 

[Bosunsmate]

Went to Ql78 plugs color cleaned up compression is 123-129 with bottom cylinder being 126.
engine died when loading on to trailer and when i removed the plugs they seem to be wet.
Maybe the float is set a bit high.
How would I do a pressure test?
Thanks Tony

Light that wetness with a lighter, if it doesnt burn its water.
If it burns check that your primer bulb holds firm with engine off and check your spark

 

[flattop1]

did not burn: dipped it in the weed wacker tank big difference.
I guess the heads need to come off. any way to guess which one ?
Thanks Yall

 

[Bosunsmate]

might be the exhaust plate gaskets