I just checked my compression ,What do you think??

[PULLNIT]

I just did a compression check on my 1989 Johnson 150.The motor was cold and in the winterized state still fogged.I got a reading of 90lbs on all six.I used an old sears gage.So,is this to low of compression or could it be due to being cold and winterized.And while I am asking what is your oppinion about decarbing-do or dont.<br /> Thanks John

 

[12Footer]

Re: I just checked my compression ,What do you think??

Hi, John. The compression may be on the low side, but the most important thing, is that the readings werre equal in all 6.<br />In the fall,decarb it,and see if your numbers go up. I suspect they will, just wonder (as you do) if they will all go up equally. But I would judge it to be in fine shape,given that it's still"on-ice", and the jugs are dry and cold. I have seen two of the same make/model guages give totally seperate readings, one 10LBS under the other. My employer's garage still uses them both.

 

[Dhadley]

Re: I just checked my compression ,What do you think??

Hey 12 -- Use one gauge to buy motors with and one to sell motors with. LOL! I had a buddy who had two of the same make that were 20 lbs apart. <br /><br />90 isn't that bad on a V6 cross flow especially if you have late model heads. Thats what compression I have on my cross 150.<br /><br />Good luck!

 

[ODDD1]

Re: I just checked my compression ,What do you think??

yep.. got 5 comp guages in our shop...the best [a snap on] stays under the bench most of its life...the gauges used for daily service are tried against this one on a bi monthlty basis...they do change with use...especially if you happen to get a cylinder full of water! these units get used hard...get screwed into motors 5-7 times a day in the summer.....

 

[G DANE]

Re: I just checked my compression ,What do you think??

Hi guys !<br /><br />Did they reduce compression on newer cross-flows. When my 35Hp 1984 broke down 2 years ago i bought a powerhead from a much newer model at a dealer, lying with a broken cranck at flywheel ( due to overreving ). When assembling, i notised the combustion chambers were roundshaped, compared to the older sharpedged. I mesured volume with oil, and it was 10% larger than old type. However i used the new head, and she runs great. When i mesured compression this winther, it was 115 on both cyls. I tried to mesure my 1984 25 HP ( same powerhead as 35 ) and it gave med 125 on both !!! Both cold - no oil. Thats why aformer asked for the difference, and if putting old top on would increase HP.

 

[G DANE]

Re: I just checked my compression ,What do you think??

Hi again<br />I gave the wrong numbers, it was 125 on the 35HP and 133 on the 25HP. What is the standard compression to expect.

 

[mrm]

Re: I just checked my compression ,What do you think??

Thats good.