Compression numbers

drtyTshrt

Seaman
Joined
Jan 15, 2013
Messages
58
I have head gaskets on order.
I hope that to be the case of a overheat at idle condition I have been chasing.

I had 118 PSI across the board when I bought the motor.
I have beached it and tried to carry it back with me once but I never have had many buzzers and always at idle.

The pee hole does not pee at idle but steams.
New thermostats.
New poppet valve.

Mercury certified mechanic installed the last water pump.

I have question about the impeller now because I did not have water running when I did the compression check.
I counted to twelve on each test.
 

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Baylinerchuck

Commander
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Jul 29, 2016
Messages
2,726
Dumb question perhaps, but is it possible you installed the t-stat backwards. Cyl 3 is definitely concerning IMO.
 

drtyTshrt

Seaman
Joined
Jan 15, 2013
Messages
58
Dumb question perhaps, but is it possible you installed the t-stat backwards. Cyl 3 is definitely concerning IMO.
I put new T stats in when I bought the motor.
Never had any issues until I beached it. That was a bad day but I never have run overheated for a very concerning amount of time.
I just replaced them again and gutted the new old ones.
When I bought the motor the T stats were gutted.

I tried the new T stats installed correctly and still the same issue so I installed the gutted ones and still had a buzzer at idle.

I do not want to pull the foot and this compression check was just a new idea to try and form a diagnosis.

I will not pull the head until the gaskets arrive.
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Sounds like you have some passages in the divider plate blocked as water comes thru it first before it gets to heads.....
 

drtyTshrt

Seaman
Joined
Jan 15, 2013
Messages
58
Sounds like you have some passages in the divider plate blocked as water comes thru it first before it gets to heads.....


I thought about that and it would be my nightmare. Do you have any suggestions? Can I see better when the heads are off?
I packed it pretty good with sand but flushed it out even with the poppet out.

The water pump was rebuilt and the case gears pulled and found to be good.
How many 12 second compression pulls can I get on a water pump impeller while spinning it dry?
 
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ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
The water pump will not be harmed by doing a compression check, so that's not a concern.

​Pull the heads off, this will tell you what the damage is, they need to come off anyhow.
 

drtyTshrt

Seaman
Joined
Jan 15, 2013
Messages
58
No Title

I got my head gaskets in today. Here are the photos. I believe the the head gasket is blown, and there is also much calcium build up for lack of better term on the passages.

Back story here as well.

I mentioned before that I checked the compression before I bought the motor. Since I that check I have learned and discovered much. One discovery was broken metal reed valves. I think that I can see where the reeds ended up. I put CCMs reeds in the block 2 maybe 3 years ago.

I am going to prep the block and re-install the head with a new gasket and see what the numbers are.
 

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gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,585
I got my head gaskets in today. Here are the photos. I believe the the head gasket is blown, and there is also much calcium build up for lack of better term on the passages.

Back story here as well.

I mentioned before that I checked the compression before I bought the motor. Since I that check I have learned and discovered much. One discovery was broken metal reed valves. I think that I can see where the reeds ended up. I put CCMs reeds in the block 2 maybe 3 years ago.

I am going to prep the block and re-install the head with a new gasket and see what the numbers are.

Make certain that the head and the block are flat and straight. Use a known good straight edge to verify both. JMHO
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,048
Any more pictures of the top of what you call # 3 piston.-----It is actually # 5 in motor speak.
 

drtyTshrt

Seaman
Joined
Jan 15, 2013
Messages
58
No Title

I don't see any indication of a blown gasket...


I thought that this little area along with the black sooty color was and indication of a blown head gasket.
Also the top of cyl 5 piston is in this photo.

All of these photos are of cyl#5 with 80 PSI of compression.
 

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Dukedog

Captain
Joined
Oct 6, 2009
Messages
3,235
head is junk unless ya know a good welder and machine shop.............
 
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