79 johnson 100TLR79S 100 HP lost compression and this is piston help ?

[ceddon46]

Re: 79 johnson 100TLR79S 100 HP lost compression and this is piston help ?

update , pulled the bypass cover off this weekend and found that the top ring was gone , so ring broke and done the damage , so now I have the task as to why the top ring has broken twice on this cylinder , going to pull carb again and go through the water passage , I have to agree it must be over heating but why is the million dollar question....

 

[daselbee]

Re: 79 johnson 100TLR79S 100 HP lost compression and this is piston help ?

I have to agree it must be over heating but why is the million dollar question....

You have been told why. The water deflector.

 

[ceddon46]

Re: 79 johnson 100TLR79S 100 HP lost compression and this is piston help ?

Question then since you are 100 % sure it's deflectors causing overheat issues , there are 2 holes under power head that allows water to come out when thermo are open , and when I lost cylinder I looked to make sure water was coming out tell tail hole which there was, I noticed there was good water flow out both thermo holes under power head , steady flow out both , so if deflectors were restricting water flow enough to cause overheat could that be possible ?

 

[emdsapmgr]

Re: 79 johnson 100TLR79S 100 HP lost compression and this is piston help ?

If the cylinder runs lean, it will overheat internally. In this situation, the overheating cylinder will usually not set off an overheat warning horn. Could be either a lean carb, or misplaced diverter in the cooling passages.

 

[daselbee]

Re: 79 johnson 100TLR79S 100 HP lost compression and this is piston help ?

Yes it can. You see there are two sides to the water jacket. Water can flow on the left side can't it? But I know that as swelled up as that deflector is, (by your pictures only) that it looks like it will restrict the water flow down the right side of the water jacket. The deflector is placed there to prevent water flow thru the 3/8" gap between the cylinders, not to restrict water flow along the sides. Look at EMD's very clear pic above of how it is supposed to look. Then compare to yours. The deflectors direct the water flow in a very specific, designed flow pattern. That deflector is blocking water flow when it shouldn't. (By your pic...) And yes, I am 100% sure that is the issue. (again, based on the picture you posted). I have seen it many times before...same thing. These crossflows are prone to that exact failure.

 

[ceddon46]

Re: 79 johnson 100TLR79S 100 HP lost compression and this is piston help ?

K thanks , this will be the 2nd time in a month that I had to tear it apart for this cylinder , want to make sure cause dont want a 3rd time I think I will pop the other head of on the other side and replace them as well..Thanks again all for the help !!

 

[daselbee]

Re: 79 johnson 100TLR79S 100 HP lost compression and this is piston help ?

Can you please shoot and post another pic of the deflector in question...one that is straight on vertical to the deflector, showing any clearances at all that exist between the deflector and the cylinder/block surfaces? Just like the pic that EMD posted above.....