Posted by NRVVA on 05/31/14 - 5:13 AM
#1
I have an 85HP Johnson Javelin, model 85ETLR76G, on my 1970 Currituck that is for sale, and a potential buyer wants a compression check run on the engine, which I think is a 1976 model year?
The engine probably does not have 10 hours running on it in the last five years and has not been run in the last two years, except on the muff in the driveway each year to fog it for storage. It has always run fine and started promptly every spring and has always run strong in the past when on the water.
I did a cold compression check yesterday and got readings of 105, 90, 100, and 95 psi in the four cylinders. I pulled all the plugs and cranked the engine , on the muff with water running to it, until the gauge reached its obvious top reading for each cylinder. I called my local boat shop that has done a lot of work on this boat, and they said those compression readings sounded ok, and that they thought that particular engine is a "low compression" engine. I cannot find any information on that through a Google search. Does anyone have any insight into that idea?
I have started and run, briefly, this engine twice in the last three weeks after winter storage and I intend to take it to the water today and give it a good run with fresh gas and some Seafoam to clean it out.
Should I get a more accurate compression check reading, either cold or hot, after running it a few hours on the lake to "clean it out"? What readings would indicate a good engine, and what readings would make a potential buyer hesitate on purchasing this engine?
Any feedback and suggestions will be appreciated Thanks.
Steve
Edited by NRVVA on 05/31/14 - 5:15 AM
Posted by jw0287 on 05/31/14 - 5:46 AM
#2
No insight to the specific motor.
Running on muffs is different than in the water.
The difference of 90 and 105 is greater than 10%.
So it may not perform well in the water.
One of my previous evinrudes did perfect on muffs and could barely idle in the water.
It had a difference of 20 psi in cylinders, and if i got it to shift to forward at high rev, i could run it.
But it was annoying skamming it in to gear at high rpm so it wouldnt stall. So i sold it as a parts motor.
Yours may be ok with a difference of 15 psi. Inform the buyer, see if you can water test it, and or giant trash can an put it in gear if clearance permits.
Btw, 90hp 1986 johnson vro is what i had.