[fish4970]

my readings are as follows #1-#6 137, 140, 137, 137, 140, 137as i understand, it is good if there is no more than 15% lowest & highest cylindermy question is what is the factory compression.i have an oem manual but it says nothingabout compression.ps motor supposedly has 6 hours on overhaul with weisco pistonsthanks in advance

[G DANE]

Hi fish4970You will definately be fine. New compression probably between 135 and 140 on most mercs of these vintages.

[JB]

Howdy, Fish.The reason manufacturers usually don't specify compression readings is that you can get different readings if:You use different guages.You use different techniques.The temp of the engine differs.The time since decarbing differs.As long as all of these factors are the same for all cylinders, the differences from one cylinder to another will be consistent, and will indicate any sick cylinders.Most engines are fine as long as all cyl. are over 100 psi and span less than 10-15%.

[fish4970]

thank you very muchi just overhauld the carbs set the timing to factory specsjust need to rebuild water pump & go fishing

[fish4970]

I HAVE A GOOD QUESTIONI CHECKED THE WATER PUMP BECAUSE OF NO TATLE TALEWHEN I TOOK THE WATER PUMP APART, IMPELLER LOOKED OK TO ME (ALL VANES INTACT & SNUG AGAINST SLEEVE)SO JUST FOR GRINS I HELD A GARDEN HOSE TO THEPIPE THAT GOES UP THE SHAFT HOUSING TO THE POWERHEAD, THE RESULTS WER LOTS OF WATER RUNING OUT OF THE DRIVE SHAFT TUBE, SOME WATER OUT OF THE EXHAUST TUBE , AND A LITTLE WATER OUT OF THE TATLE TALE IS THIS NORMALI WOULDEN'T THINK THERE SHOULD BE WATER IN THE DRIVE SHAFT PASSAGETHANKS IN ADVANCE fishertodd1@msn.com

[jim dozier]

Tilt the engine up and do what you did with a flashlight shinning up the driveshaft housing and verify where the water is coming from. Are you sure it wasn't coming from the exhaust housing?

[fish4970]

i am pretty shure that it was coming from the drive shaft passage there is a partission between it & the exhaust itlooks like it goes all the way up

[jim dozier]

If you're correct, I don't think water should be spraying in the driveshaft housing. I don't know your engine but I would suspect the seal/grommet at the top of the water tube or the powerhead seal is leaking.

[fish4970]

it is a 1978 mercury 175 black max

[fish4970]

would the water pressure relief valve affect theamount of water from the pee hole

[fish4970]

would like to hear what jb thinks

[JB]

Thanks for the confidence, Fish, but this is one I don't know much about.12Footer knows Mercs pretty well. I wonder what he thinks.

[fish4970]

how about it 12footer do you have any insite on this subject