1972 Johnson 65hp

[tashasdaddy]

Re: 1972 Johnson 65hp

if not mistaken, all the connecting rods on those carbs are snap in, if you don't readjust them, and reinstall the way they came off, the carbs should not need to be sinc'd, every thing should fall back into place.

 

[HighTrim]

Re: 1972 Johnson 65hp

Agreed. The link n sync on that motor is not as hard as you may think. I truly think that a thorough carb cleaning along with a link n sync will fix you right up. When you are through ensure the carb adjustments are correct as per your manual

 

[jay_merrill]

Re: 1972 Johnson 65hp

Your probably right. I just picked up a spark gap checker and had a nice fat, 1/2 inch spark on all three. Unless the ignition is breaking up at higher rpms, it would seem that it has to be fuel.

 

[HighTrim]

Re: 1972 Johnson 65hp

I concur If it was acting up after warming up, it could be a faulty ignition component heating up and failing. The fact that it does it cold or warm, when the throttle is applied is leading me to believe fuel delivery.

Another test for a rainy day.

Get a vacuum gauge and install it inline on the fuel hose before the engine along with a clear section of hose. Start the test run and note the readings on the gauge and monitor the fuel flow through the clear hose.

Results:

-Vacuum of less than 2 inches and air bubbles in the clear hose indicates an airleak into the fuel system
-No air bubbles and less than 2 inches indicates a bad fuel pump
-Vacuum over 4 inches indicates a restriction in fuel delivery

Sample Gauge

"http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&sspagename=STRK%3AMEBTOX%3AIT&viewitem=&item=4610113711&_trksid=p3984.cTODAY.m238.lVI"

 

[jay_merrill]

Re: 1972 Johnson 65hp

I had some time to fool with the motor again today. It appears that I still have two problems. The center cylinder ignition is still breaking up. I used a timing light on all three again just to see if I noticed anything that I didn't before and, bingo, the #2 cylinder is definately misfiring and it did it both cold and warm. I know from the ohms test that the timer base needs to be replaced so I am going to do that soon.

I also did the spray bottle test with mixed results. A moderate spray overloaded all three cylinders and a light spray made a very minor difference in the lower cylinder. I was going to try the test which makes use of the timing light to see what the nozzles are doing but really didn't have to - the spray pattern was clearly visible in just natural light. What I saw indicated that there was a significant difference in the amount of fuel coming out of the high speed nozzle on the upper cylinder v. the middle and lower, with the lower being the worst. Looks like its time to pull the carbs and clean them up.

 

[jay_merrill]

Re: 1972 Johnson 65hp

I was fooling with the boat today and it popped into my head that I had never finished answering this thread. So here it is ...

The ignition problem was as I suspected and as soon as I replaced the timer base, the miss went away.

I pulled the carbs without disconnecting the linkages and laid them on my work bench in order to pull the bowls on the middle and lower carbs. I also did not fool with the low speed needle valves since there was never any indication of problems at low power settings. Both bowls were spotless with no hint of varnish, etc. I pulled the fixed, high speed valves with mixed results. The middle carb's high speed valve showed no visible obstructions but I blew it out anyway, along with the recesses in the bowl. The valve for the lower carb was blocked by a fairly good sized hunk of something that looked like white plastic. This was removed by passing a thin wire through the valve from the other side. How this piece got in there is a bit of a mystery because it was large enough that the screen on the fuel pump should have stopped it. Because it did, however, I have installed an inline fuel filter in the fuel system with a screen that is fine enough that not much of anything other than fuel should get through it.

Just to back up a bit, the motor ended up with three problems at once - the two bad coils, the bad timer base (one bad sensor in it) and the fuel problem. Although this made the diagnosis a bit confusing, all is now well. The reinstallation of the carbs was a snap and changing a timer base in that motor is easy - about a 30 minute job.

My good old Johnson is back to running like a champ and I am so glad that it is not a new motor that would have had to go to the shop. This repair was inexpensive, easy and afforded me an opportunity to get to know the motor a bit more.