"Newer" 25/35hp OMC compatibilities

[fleetwin]

quote Mumbles:

Here’s an external coil on a ’72 20 horse Evinrude I had. The coil was badly cracked and leaking but the motor still ran!

That one looks like it has some life left in it, how much do you want for it??

[johnyrude200]

quote fleetwin:

Will try to address each of your questions, let me know if I mess up:

I’ll give all your suggestions a try tomorrow (just acquired a lot of motors and am processing for next season…believe it or not). With the fuel pump, there was no pump on the motor and the one I put on it closely resembles your standard 25/35 ones (not the small square one, but the more modern ‘house’ shaped one with a point at the top).

The gearcase was off the motor when I purchased it, I did not see any evidence of issues with the gearcase and did the standard new impeller install. The whole mud dubber thing was discovered by chance when I went to change the thermostat, only to find that they had infested the water jacket and T-stat cover, along with the final water outlet at the bottom of the cover. I am questioning whether there is a big nest under the powerhead, because as I mentioned before, there was a overheat situation the first time I ran it because water could not escape due to the clog under the powerhead. Then WHOOSH, a big clump came out of the two upper exhaust water holes, and then the motor ran at correct temperature. I also have had a persistent overboard water indicator clog that keeps coming back, so I suspect they may have made there way up the exhaust and water tube inlet, and infested those areas of the motor.

We’ll know by end of day tomorrow! (CHECK OUT my other post for one of the motors I processed earlier today…and are continuing to process).

[johnyrude200]

Mumbles: Please tell me that I’m wrong when I say…is that picture of sparks in the coil!

WOW…if it is.

[Mumbles]

Yup, those are sparks! 😯

I had to take about ten pics with the motor running to even get one which showed the sparks jumping around! It’s all to do with the timing. Now that I think of it, I’m sure the motor was a ’73, not ’72. 72’s still had internal coils.

[johnyrude200]

that’s like trying to catch a picture of a lightning bolt, but at least you know where it’s going to be over, and over, and over again.

[fleetwin]

OK, so the gearcase was off. There is a long inner exhaust snout that goes half way down inside the exhaust housing, no real restrictions, so I really don’t think a plugged exhaust is an issue. I’m guessing that the stuff in the cooling system is more like plain mud/sand, and that the previous owner ran the engine through muddy bottom to plug up the passages this way. The gearcase was removed from the engine probably due to previous attempts to unplug the cooling passages.
Can you loosen the telltale elbow easily? If you can, I would simply remove the elbow and run the engine, this will allow all the debris to spill out of the manifold. Again, don’t force that elbow and break it off in the exhaust cover.

[johnyrude200]

I’ll give that a try later today (7 more motors to inventory for this winter first). What I want to mention is that there were mud dubbers nesting in the thermostat cover when I removed it. The water outlet hole at the bottom of the cylinder head was pretty much clogged solid. It appears this is a non-issue now since a big glob of gunk fired out the exhaust relief/blubber hole at the top of the exhaust housing.

But I’ll agree with you on that about no clogs in the exhaust. Interested to see if it was just a float setting…it was off by about 2mm (using the special tool for setting the float). Those mouse/seized motors have been keeping me occupied yesterday and today!

[johnyrude200]

Finally got back to working on my personal project. So I’ve had the motor running continuously for the past 45 minutes and did a number of trials at WOT throttle. I adjusted the float setting, and verified that test wheel RPM’s (via a ’79 service manual) are supposed to be 5300RPM.

I was able to hit 5600 RPM today, so I am guessing it may have just been a float setting issue.

Now all I have to do is figure out why there is an intermittent water clog going on inside the water jacket. I keep catching the motor running too hot (180-200°) with almost no water flow out of the blubber holes. I shut the motor down for 30 seconds, restart, and then water starts flowing again and the motor operates at the correct temperature.

I installed a brand new thermostat before I even ran it the 1st time, so I may dig into the exhaust bypass cover to make sure there isn’t mud dubber houses in there.

[dan-in-tn]

Besides your possible clogs, keep in mind this engine has a guide #321515 NLA for the water tube up against the exhaust snout. When this motor sees an overheat that guide melts and the top closes up. The grommet #302497 at the top melts also. Both can cause an obstruction for water flow to the powerhead. The motor will usually get enough to run at idle and maybe keep up for a short time, but then overheat. The guide and grommet are ref #s 114 &115 on ME. I found a couple of guides on Ebay a month ago. Just keep that in mind as you go hunting for your overheat problems with these early 35hp motors.

Dan in TN

[johnyrude200]

I’m getting ready to run it with no thermostat to see if it was a faulty thermostat. What has me itching my head is that it was running at WOT continuously for 2-3 mins and had no overheat issues (Ran fine at 143-158, temperature dropped quickly upon throttling back), yet I’ve seen it get hot, as if there is no water circulating around the cylinders, a handful of times.

The water from the telltale gets real hot during this situation, and from experience that tells me water isnt circulating, yet it’s pumping tons from the telltale.

Borrowing a page from my learning curve with the 9.9/15’s. Oh joy, good to know these bigger 25/35 motors act the same way with their water tube grommets.

Thanks for the reminder, and head’s up Danny, I remember you mentioning this to me several months ago, but had forgotten until now.

Will report back shortly.

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