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JOHNSON V4 115hp

coldoc

New member
"Help!!! The engine runs fine

"Help!!! The engine runs fine at idle, little bit racy but no overheating etc. Reverse is fine but when i put it in to forward the engine stalls and will not start again. I have changed many items on this engine HT Leads, Ignition coils, new fuel tank/lines, spark plugs and new battery cables. It will be something simple i know but cannot find the fault. The engine is middle 7o's."
 
"Rather than throw parts at th

"Rather than throw parts at the engine, trouble shoot it, starting with the basics.

What is the model number?

What is the compression of all cylinders?

With the spark plugs removed, does the engine have spark on all cylinders AND just how big a gap will that spark jump on the individual cylinders?"
 
"when i bought the boat the gu

"when i bought the boat the guy had just had one of the pistons replaced, have receipts. the comp tester can be purschased from car shop, is that correct? I recall that you place the tester in the cylinder and crank the engine and take readings over 3 cranks, is that correct? the gap on all the spark plugs is 0.7mm which is 0.03". the spark plug has to be removed and earthed on the engine to test for spark, is that correct?
I have undertaken the work myself as a learning curve and challenge but getting to the point where i should get a marine mechanic to check it over, i think."
 
"You're thoughts about com

"You're thoughts about compression are correct.

Testing spark.... plugs removed, must use a tester, gap must be 7/16".

(Spark Tester - Home Made)
(J. Reeves)

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:


..........X1..........X2

.................X..(grd)

..........X3..........X4

When time permits, visit my store at: http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"
 
"Hello Joe, I have checked th

"Hello Joe, I have checked the compression today.
checkd in the following order O represents cylinder, O1 70bar O2 95bar and sparkplug stiil new not blackish like other cylinders.
O3 110bar O4 105bar
Tryed starting after comp check and not even firing now.
Have not checked the spark yet but suspect cyl 2 is not sparking because plug is not blackish like the others.
Colin"
 
"Colin.... I don't know wh

"Colin.... I don't know what you mean by "bar" as in "70bar" etc, but I assume it relates to "psi" (pounds square inch).

If so, there is a 40bar (40psi?) difference between cylinder #1 and cylinder #3 which is unacceptable and spells out "Major Overhaul".

Unless we have a lack of communication pertaining to the above paragraph, it is time to remove the cylinder heads in order to inspect the head gaskets, pistons, cylinder walls, the undersides of the cylinder heads, and the head & crankcase sealing surfaces."
 
"Sorry Joe, yes it is psi. I

"Sorry Joe, yes it is psi. I thought as much. But the engine was overhauled last october, i still have the receipts will call them and see if it still under warranty. The o/haul was approx $1000. Wonder why it is not firing now?
Thanks
Colin"
 
That non firing problem will o

That non firing problem will of course need to be corrected BUT the compression problem needs to be looked at first.
 
"Joe. i have a parts list from

"Joe. i have a parts list from the last piston change and engine overhaul
1. 393271 std piston
2. 394930 ring set
3. 318358 head gasket
4. 321727 bottom gasket
Are these correct, the engine model is early 70's 115hp V4.
Colin"
 
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