Compression test dry or wet?

SpinnerBait_Nut

Honorary Moderator Emeritus
Joined
Aug 25, 2002
Messages
17,651
Re: Compression test dry or wet?

Let me jump in here and say let's chill on the personal attacks.
Let's give the right info so the original poster can make some sense out of the thread.

One person say's this way and another say's that way.
I have always been told by the merc people, never turn my engine over dry and I don't.
Either on muffs or in water.
Ok, I'm done.
Be cool now.
 

ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: Compression test dry or wet?

My 2 cents worth:
The readings don't change with the throttle plates closed or open on a two stroke. No need to argue, try it yourself;
The test should be done with all of the plugs removed so that the speed is optimized;
The SAFEST bet is to keep the impeller wet with your muffs on or in a barrel;
A screw in type gauge is best;
Readings on a cold engine can vary as the fuel mixture gets pulled in. Better to warm it up and let the oil distribute evenly;
 

iwombat

Captain
Joined
Jul 12, 2006
Messages
3,767
Re: Compression test dry or wet?

I usually do it cold, with throttle plates closed. Hit and miss on the water, depends on where it is and what's available.

If I get uneven readings I'll warm it up (with water) and try again.

Yes, it's _better_ to lube up the pump with water. You'll more than likely take some kind of life off of it. I replace my impellers at least every other year anyway, so shortening the life by 20 hours due to one dry run isn't that big of a concern.
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: Compression test dry or wet?

I agree ezeke, it only takes 20 secs to hook up the muffs, why put undue stress on your water pump /impeller when you dont need to. You can argue all day long that running it dry wont affect the integrity of the impeller/housing, but you cant argue the fact that running it wet wont hurt.
 
Joined
Jul 19, 2007
Messages
5
Re: Compression test dry or wet?

Yall need to chill a bit.. Here some comical relief for ya

arguing.jpg
 
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