Re: 9.9/15 impeller housing tricks?

[johnyrude200]

Donny!!!! and…FRANK!!!

Glad to see you both on here. I was getting lonely. Don, I laughed at the end of your post when you ended it with "sorry." We’ll both have a good laugh at Rocky Hill about this one in about a week.

The motor is a ’78 15hp Johnson. 1 pull starter. It was a salt water motor, however, it’s still in pretty good shape. Believe it or not, every screw was still loose, except 1 head bolt which I twisted off even after heating it for a solid 10 minutes with the torch, and I’m in the middle of drilling it out and retapping. I pulled the powerhead today, inspected both the water jacket where the tell tale is, and pulled the head and thermostat cover.

There really wasn’t anything clogged up in there, the telltale did have a minor blockage (it was dripping water pre-teardown), but I’m still working my way back to figure out where water flow is being impeded. A little pitting in the water jacket baffle. Those gaskets were shot though and I replaced both, they had holes in the wrong places if you know what I mean.

The thermostat appears OK, and before pulling the powerhead I hooked up a hose to the water tube and water passes through the motor freely. However, it seemed that very little water was getting past the thermostat to the exhaust when I ran the motor, and pulling the t-stat cover showed very little moisture was circulating past it. It was only taking a minute to get it to an overheat condition (and I dropped my laser heat gun in the test tank last week without realizing it…then ran a motor with a regular prop and WACK WACK WACK…minced laser gun…so back to ‘ol faithful…the thermomelt stik, which I used everywhere on the motor…thanks for the advice last year FRANK – New laser gun on it’s way from ebay).

I ran some weedwacker wire up the tell tale a few times before posting this yesterday, and also ran the motor a few different times and the same overheat condition was happening. The impeller is OEM. Impeller housing has a metal cup inside of it (I’m guessing this was normal for these, whereas I’ve seen that as an update on some smaller motors i.e. 2hp).

The grommet on the exhaust tube appeared OK, not folded in (a little tired, but still serviceable). So once I have the cylinder head on, I’m going to try running the motor with no thermostat. I think somehow that it isn’t opening at all. What’s strange is it isn’t stuck, but I can these fail to open after awhile? It’s probably an original although it appears OK (even the gasket is still soft). Either it’s that, or something going on in the gearcase that I missed. When I replaced the impeller, it appeared that there was a very thin gasket between the housing and the steel plate underneath it. This gasket appeared worn, but I figured with all 4 housing screws tightened down that the gasket was basically overkill. The other thing – to confirm – there is no water bypass on these motors? I put my thumb over the empty thermostat hole when I was running water through the motor from the garden hose and it pressurized the water system and effectively cut off water flow. Of course, the tell tale started firing water out rapidly.

I’ll double check the impeller housing, but FRANK…I removed the water tube grommet at the impeller housing and apparently this motor does not feature that slanted vent hole. There was no access hole that I observed (unless I overlooked one through where the ‘ears’ on the grommet are) to do a clean out. I sure hope this wasn’t the issue, because I may have created a lot of work for myself over nothing…but I do know these motors inside and out a lot better then I did 24 hours ago (should come in handy because I have 9 more to go through!). There is a hole on the outside of the housing which leads to the impeller cavity. I am assuming this is set up to accomplish the same as the 18-20-25’s.