Compression on a Powerhead

[Jack Daniels]

Is it possible to check the compression on a powerhead without having the ignition system installed, the powerhead connected to the outboard, and the flywheel disconnected. I just bought a new powerhead and want to know if i need to rebuild it prior to starting the process. Thanks

 

[Kajun37]

Re: Compression on a Powerhead

you've got to be able to turn it over somehow...you should of tested the new powerhead before you bought it.

 

[Frank Acampora]

Re: Compression on a Powerhead

Well, Jack. You do know that it is possible to do anything you want as long as you want to badly enough and throw enough cubic money at it.

However, since everything seems to be disconnected, why don't you just pull the head and look at the bores? If they are not scored, the chances are that the compression will be adequate. If you have one of those flexible thingies, you don't even need to pull the head--just look in the plug holes.

Little trick I sometimes use when I feel a bit lazy--bend a piece of welding wire 90 degrees on one end about 2 inches long. Stick it in the plug hole and rotate it around the bore. You will be able to feel any roughness due to scoring.

 

[Jack Daniels]

Re: Compression on a Powerhead

THanks Frank yorur the man. I dont care if the compression is bad or good, i am kinda hopeing its bad because i really want rebuild it. I just want to know where i stand before i start. I bought the power head for 50 bucks and i am planning for a rebuild for learning if needed.

I might just take off the entire head and check her out, ill post some pictures and ask for your advice. Thanks

 

[Lakester]

Re: Compression on a Powerhead

frank A sez:

"Little trick I sometimes use when I feel a bit lazy--bend a piece of welding wire 90 degrees on one end about 2 inches long. Stick it in the plug hole and rotate it around the bore. You will be able to feel any roughness due to scoring."

interesting! i have never done that. does the owner stand by and say, "sure frank, go ahead, that's ok with me?"

wondering...

regards,

lakester

 

[Lakester]

Re: Compression on a Powerhead

jd~

a powerhead for $50?? !!! well, i'd say u stand... pretty!

if crank and rod bearings look good, and bore mics within spec, no doubt u will have good compression short of a stuck ring... even if u used the old rings.

if it was mine, i would not even worry about a CR test

regards,
lakester

 

[Frank Acampora]

Re: Compression on a Powerhead

Oh, no! I only do that on engines I have bought for myself. And it's only a rough diagnostic procedure. As I have said before, when I work on someone else's engine, I take no short cuts.

 

[Lakester]

Re: Compression on a Powerhead

OIC

lakester

 

[Jack Daniels]

Re: Compression on a Powerhead

Ya i think i got very lucky. The guy that sold it said it came off a working outboard that was stripped of all the ignition parts and the flywheel while he had it in storage. He didnt want to deal with the repairs so he just sold it. He also has the lower unit available for 50 bucks also. Im thinking i should also pick it up becuase you never know. But its the same engine that i run now so the thought was, i can rebuild it if necessary and then when the current head that i have now dies i can just switch out the parts that i need and replace with a rebuilt head. Easier on the pocket book doing it slowly over time than all at once. Plus i think i can learn alot about the outboard doing it like this, but egads, i might have lucked out and bought a head that was in good shape. Ill let you all know what i find.

 

[Frank Acampora]

Re: Compression on a Powerhead

Lower unit for 50 bucks? Snap it up! The case alone (if it is in good condition) is worth that.

For example: if you break a skeg, it will cost 90-100 bucks to repair it. So---just swap lower units. If the gears are no good, swap the good set into the good case. Save a couple of bucks.

 

[Matthew A.]

Re: Compression on a Powerhead

Did somebody say...SCORE!!!

Another manner of getting a looksy [if only partially] at the condition of the rings and bore is to simply remove the veiwports on the intake side of the block. Doing so allows one to partially see the rings, ring grooves and one half of the piston skirts and bore directly.