'72 Johnson 65hp questions/ concerns

[Chaz1]

I have a '72 Johnson 65 hp motor with coils that have cracks on them probably due to age. How concerned should I be with these cracks. The motor runs real strong and so far reliably.

Also, how often should I replace the impeller on this motor. It's hard to tell how much water is being run through the motor because there is no pee-hole to watch. It does not run hot at all but I sure don't want to make that fatal mistake. And how much work is involved in replacing that ? I wouldd imagine that after dropping the lower unit to replace the impeller, I must also replace the lower unit gasket.

Does anyone have any input in regards as to the reliability of this motor? I've had this motor for only one year. I put it in the local marine shop when I bought it. Told them to check it over and they said it all looked real good. Compression was I believe 113, 110 and 110.

They electra shift operates very well. I just purchased the Johnson premium lower unit gear oil for it yesterday so that's on my list of pre-season things to do.

Lastly, I would like to find the original cowl for this motor. Someone has replaced the original with a 60 hp Evinrude Triumph cowl. Fits perfectly but, well, ya know!!!!!

 

[tashasdaddy]

Re: '72 Johnson 65hp questions/ concerns

hope that is premium blend type "C" gear oil. impeller 2-3 years, those coils are going to fail if the are cracked, at the worst time. you could add a tale tell, see faq forum, there is not much to changing the impeller, the hardest part is not injuring the wiring to the lower unit. they are great reliable motors

 

[patrick4266]

Re: '72 Johnson 65hp questions/ concerns

I have a 1972-85hp rude with the electric shift and I just replaced the impeller yesterday. I do not believe there is a lower unit gasket but I am not a outboard mechanic, the other guys will know more than me. I did mine out in the yard with it tilded up.I actually had to do it twice as the first time I used vasiline on the drive shaft spline and I was told by high trim that I should use marine grease. I wanted to do it right so I did it again. What was tricky for me was lining up the plastic guides for the water pump so I used a rubber bungy cord to hold it from slipping as i did it. Another thing that really was tricky was getting the wire back up in the little hole. the first time it took me a couple of hours. Second time I tied a piece of fishing string on the wire before I pulled it out then I was able to take a piece of guide wire back through the hole and it was a lot easier for me. First time off and on in three or four hours second time about a hour.

 

[jay_merrill]

Re: '72 Johnson 65hp questions/ concerns

Chaz, as you know, I have the same motor. Mine has been very reliable with the exception of some problems that I had to work through not long ago. One problem was caused by junk in a carb but the others were all ignition related. Since all of these things happened at once, troubleshooting was a bit of a drawn out process.

In my opinion, you should just go ahead and replace all three coils. If you buy OEM coils, they will cost about $38 each. I don't like the spark plug wire/clip/boot kit that comes with them so I use automotive type wires with the spark plug boots installed by the manufacturer. When you replace the coils, be sure to ground them properly. Also, they will come with wires to connect to the power pack that are too long because the same coils were used on other OMC motors. I shortened mine by cutting the wire at an appropriate length. If you do this, however, be aware that the ring terminals used on these coils have a longer than normal "neck" on them. You can not use standard ring terminals because they won't fit in the recessed portion of the powerpack properly. Your local OMC/Bombardier dealer should have the correct terminals in stock. One little trick that I will pass on to make your life easier later, is to use narrow cuts of shrink tube (you can get this at Radio "Snack") to make bands for each wire, indicating what cylinder the wire corresponds with - one band for #1, two bands for #2, three bands for #3.

I would also plan on replacing the rest of the ignition system over time. CDI makes a powerpack, timer base and stator for your motor. I paid about $80 for the powerpack and about $225 for the timer base. I have since seen the same timer base for about $160 so look around. I haven't replaced my stator yet because the ohms test that I did on it was right on spec, and it is working fine. I think I am going to replace it anyway next month just for peace of mind.

Check with your OMC/Bombardier dealer to to make sure I am correct but I believe the OMC Premium Blend oil that you used in the LU meets "Type C" lube requirements. TD is right though - you must use the correct oil in this LU since it is "hydro-electric." Also, a great tip that is often made here is to be sure you replace the o-rings for the fill/drain screws on the LU as these points are where many LU leaks originate.

As for overheating, you might want to do the "hot horn" electrical check to make sure yours is working. Also, the wire for the hot horn runs to the terminal block above the powerpack through the area of the #2 coil - be sure not to pinch this when you replace that coil. If it is pinched to the point of damaging the insulation, the wire will ground and your horn will sound all of the time ... and, yes, I found that out because I did it! I had to open up the wire bundle and splice a piece of wire in order to replace the wire that I damaged.

If you replace your own impeller, be very careful not to damage the shift wiring. My impeller was replaced last year when I bought my motor but I didn't do it so I'll leave out advice here. I would say, however, that I am not sure that these wiring harnesses are still made so getting a new one might be a bit tough.

Another tip on this motor is that there is a seal in the lower cowling to prevent exhaust gases from entering where the shift wire enters. It is important to make sure that this seal is not leaking because no motor wants to breath exhaust gases. If yours is, the fix is easy - just remove the lower cowl ring (four screws between the front & rear pieces and four screws from the inside of the lower cowl, downwards into the cowl rings) and seal the opening with some heat resistant silicon.

If your motor is in generally good mechanical condition, and you take care of it, I think you will get a lot of good use out of it. I have been very pleased with mine and don't blame my recent problems on the motor - it is, after all, 36 years old and cracking of wires, etc. is to be expected.

 

[rodbolt]

Re: '72 Johnson 65hp questions/ concerns

didnt the 3cyl in 72 still use the amplifier setup with points,rotor and distributer cap?
I owned one years ago but cant remember, I thought the screw terminal pack was introduced in 73 with a hydromechanical shift .
anyway be very careful with the shift wires, they tend to stick in the powerhead adapter.
last set I had to replace in the mid-ninties the harness was about 120 dollars and may be NLA no.
dont even think about a splice, I tried everything I could think of and could not make a satisfactory water proof splice.
you can look on the BRP website for a parts diagram if it goes back that far.

 

[jay_merrill]

Re: '72 Johnson 65hp questions/ concerns

Nope. The '72 65hp uses a 6 amp stator with three charge coils, a timer base, a powerpack and three ignition coils. The '71 60hp used the system that you describe. Strangely enough, the stator in this motor was 9amp - I wish mine had a little more "umph!"

PS: Chaz, you might want to decarb your motor to see if your compression increases a bit. The values that you are getting are not bad in general, and the "eveness" is a definate positive, but the older OMC triples are relatively high compression engines. Mine shows "plus or minus" 138 psi on all three "holes." In all fairness, my motor was not run much before I got it but this sort of compression is not unusual on these motors.

 

[Chaz1]

Re: '72 Johnson 65hp questions/ concerns

PS: Chaz, you might want to decarb your motor to see if your compression increases a bit. The values that you are getting are not bad in general, and the "eveness" is a definate positive, but the older OMC triples are relatively high compression engines. Mine shows "plus or minus" 138 psi on all three "holes." In all fairness, my motor was not run much before I got it but this sort of compression is not unusual on these motors.

After having read all this information on de-carbing by using (more than likely)Seafoam, I definately plan on doing this. My question is, with a motor that exhausts through the hub(as a '72 65hp Johnson does), how does the carbon burn off when it has to travel all the way down through the hub. Seems to me that a lot of that carbon build up clogs up the chambers leading to where it exits the hub. That's a long way for all that gunk to travel. I can't imagine that the lower part of the motor would get hot enough to "burn off".

I'm suprised I had never heard of this stuff. A few years ago I took a two-stroke motor performance class at a local technical college to rebuild a Tri-Z 250 three wheeler and no one ever mentioned Seafoam. From all the testimonials and positive feedback I've seen here it appears to be a great product.

On another note, the lower unit oil I purchased is the right stuff. It doesn't say "type c" but specifically states that it is recommended for the electra shift for that year of motor. So I should be good there.

I've also seen a couple of different manufacturers of coils that will fit this motor.(Sierra? and maybe 1 other) Just wondering if anyone has had any experience on the reliability/performance of these aftermarket coils. Are they owrth saving a few bucks or just stick with the OEM?

Thanks again in advance for anyone's thoughts.

 

[HighTrim]

Re: '72 Johnson 65hp questions/ concerns

As far as the decarb goes, it has been known to clog the recirc valves , as well as ruin plugs in extreme cases. I would change the plugs after, and clean the recirc valves if applicable. Whenever I service my water pump, I use that time to also clean my exhaust tube of carbon build up as well.

Concerning the coils, have never bought anything other than the OEM, so cannot comment.

 

[Chaz1]

Re: '72 Johnson 65hp questions/ concerns

As far as the decarb goes, it has been known to clog the recirc valves , as well as ruin plugs in extreme cases. I would change the plugs after, and clean the recirc valves if applicable. Whenever I service my water pump, I use that time to also clean my exhaust tube of carbon build up as well.

Concerning the coils, have never bought anything other than the OEM, so cannot comment.

Any other thoughts on aftermarket coils? Somebody out there must have used these!

Trim, do you have this motor or something different. According to my parts manual there is no recirculation valve. Keep in mind, not all motors are the same.

 

[HighTrim]

Re: '72 Johnson 65hp questions/ concerns

No I do not have that motor, nor do I believe it has recirc valves, that is why I said if applicable. Sorry, just making a general comment about the de carb procedure.

One aftermarket coil I have installed on a friends boat were the CDI's, and do not believe he has had any trouble. They did seem to be built well.