Need help: 1976 Johnson 75HP Jet 75ELR76D surging.

[Mallardslayer]

I have been having some problems with my motor maintaining full power. Here is what I have done so far.

1. Replaced all three coils
2. Replaced the power pack
3. Replaced my fuel pump
4. Replaced the spark plugs
5. Replaced the fuel hose and fitting to fuel tank

Heres what happens. I take off and the engine reves up to fullspeed and going pretty good, then it begins to miss and goes full power...miss again and it contiunes the same thing. Then is goes half-speed and surges to full power and back to half speed and back to full speed. It ends up in half speed for a while and surges again.

I was told it may be a stator, but I really don't know what to do at this point.

Any help would be greatly appreciated.

Abel

 

[Joe Reeves]

Re: Need help: 1976 Johnson 75HP Jet 75ELR76D surging.

This surge you speak of..... Is it a gradual surge up & down such as possibly an engine running out of fuel, then having fuel re-supplied to it, OR.....

Is it a sudden, instantanous, surge such as might be caused by yanking a couple spark plug wires off, then later re-connecting them?

The spark plugs should be Champion QL77JC4 plugs gapped at either .030 or .040 .

Check compression... what are the readings of all cylinders?

Check the spark... Should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it? If not explain in detail what you have.

 

[Mallardslayer]

Re: Need help: 1976 Johnson 75HP Jet 75ELR76D surging.

Th spark plugs are Champion QL77JC4 plugs gapped at .030, the surge sounds like: "It's a sudden, instantanous, surge such as might be caused by yanking a couple spark plug wires off, then later re-connecting them".


It will do that for a little bit and then it will bog down and miss again like it wants to reagin it's full capacity.

I have not checked the compression. How do you do that? Obviously I will need a guage, what do your recommend?

Thank you

Abel

 

[Joe Reeves]

Re: Need help: 1976 Johnson 75HP Jet 75ELR76D surging.

Compression Gauges with a rubber tip are fairly cheap... Wal*Mar, K-Mart, Auto stores, etc.

Spark plugs removed... shove gauge in plug hole. Crank engine over 3 or 4 times, observe reading and jot it down, also note which cylinder.

Spark... all plugs removed set gap on tester to 7/16" on that model. Crank engine over. Spark should jump that gap with a strong blue lightning like flame constantly.... a real SNAP!

(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

 

[nwcove]

Re: Need help: 1976 Johnson 75HP Jet 75ELR76D surging.

quote "Compression Gauges with a rubber tip are fairly cheap... Wal*Mar, K-Mart, Auto stores, etc".

with all do respect, dont buy one of those rubber tipped gauges that you have to push and hold against the plug hole, you will just end up buying another screw in gauge, for about 10 bucks more.

 

[Joe Reeves]

Re: Need help: 1976 Johnson 75HP Jet 75ELR76D surging.

I have both.... prefer the rubber tip gauge as it simply saves time, cranking the engine using a mechanics jumper from the battery cable terminal of the starter solenoid to the small 3/8" nut terminal of the solenoid that engages the solenoid.

 

[nwcove]

Re: Need help: 1976 Johnson 75HP Jet 75ELR76D surging.

with all do respect again.....those rubber tipped guages allow for such a margin of error . jmo, but you cant get real numbers from them. a waste of time and money ..in my humble opinion. ( spend the few extra bucks, and get a half decent tool)

 

[Joe Reeves]

Re: Need help: 1976 Johnson 75HP Jet 75ELR76D surging.

With all "due" respect, why get a "half decent tool" when I've already suggested a decent one? What the hell is the matter with you?