yet another 15hp question

[johnyrude200]

This one is an ’87 15hp. It’s overheating even with the thermostat out. Telltale is pumping a ton of water (installed a new impeller), water is gushing out of the thermostat orifice when I run the motor with no thermostat cover on it.

I pulled the cylinder head and everything looks clear. There is very little water exiting the exhaust ‘blubber hole.’ I have run weedwacker hose up the exhaust hole, and down the water exit at the bottom of the cylinder and it’s gone easily 6-8 inches.

If memory serves correct, could the water tube grommit be restricting water somehow? I’m stumped because the telltale is pumping tons, and the thermostat orifice has water gushing out. But for some reason it seems like there is a clog somewhere not allowing water to pass out of the cylinders on the outer side of the head gasket to the drain hole.

[crosbyman]

tried air pressurizing the water conduit forward and backwards

Joining AOMCI has priviledges 🙂

[dan-in-tn]

Dont forget those water flow diagrams in the back of the service manuals I sent you. They are color coded and very useful. I believe the telltale on this motor only indicates the water pump is pumping not that water is circulating thru the powerhead. If so the water from the telltale will just be cold.

Dan in TN

[billw]

I have done many a salt water water tube grommet and I recall that the telltale gave no real indication that there was a problem. You would think they would, but their indication was not always conclusive, for a grommet problem. For any overheat, we would always check the impeller first, then go straight for the grommet and do the thermostat while the power head was off, when that was so much easier. In salt water, this was almost never the wrong approach.

Long live American manufacturing!

[fleetwin]

Like Bill says, it doesn’t take much of a little opening left in the grommet for the telltale to show water.
But, in this case, the engine has two water tubes and two grommets. The second water tube is actually a short exit tube that is directed into the back of the exhaust hsg. So, it is possible that the intake water tube grommet is OK, but the exit water tube grommet is crushed. That would explain why the engine seems to pump like crazy when the thermostat cover is removed, the exit water tube is being bypassed by just letting the water dump into the engine pan.
In any event, I would bet my last nickel (if I had one), that the grommet(s) are crushed. The engine seems to show water at the telltale, and removing the head didn’t show any crusty salt.
But, this is a big job even though the grommets are only a few bucks. You might want to question the owner to make sure the grommet job hasn’t been done recently. True, this engine did have "improved" grommets, but they still were no match for salt water. Let me know what you decide to do, I will show you how to trim the new grommets a little further to make sure there are no further grommet issues.

[johnyrude200]

A couple of things I noticed; the water from the telltale was getting to be hot water when the motor was beginning the overheat. There is a very small amount of water making its way through the blubber hole/exhaust, but almost none. Shouldnt this water remain cold at all times since it hasnt circulated to the cylinders yet? It takes a solid 3-4 mins before the overheat occurs. Even at mid range RPM.

Im not sure if this was a salt motor, but when I did the impeller, it had more sand and debris buildup in the exhaust housing and impeller area then anything Ive ever worked on.

Ill ending up pulling the powerhead and examining the starboard cover and gromits and report back.

Just hope those 6 powerhead screws and 4 exhaust tube screws cooperate!

I dont think this motor has ever been worked on before, it is all original. I acquired this as a trade in so nobody to ask the history on it.

[fleetwin]

Yeah, sounds like the symptoms of a grommet(s). Sometimes, you will start the engine and notice the telltale working, but it slows and sputters as the engine heats up. Then, it will puff a blast of steam right out of the telltate when she really gets to cooking. I’m very confident you will find crushed grommets.
Before you pull the powerhead, try to determine if the upper mounts are worn/shot. You wouldn’t want to miss the opportunity to change bad upper mounts once the powerhead is off.
Good luck with the bolts, there are four more under there that hold the inner exhaust tube/grommets under there as well. Use the torch if they don’t want to budge.

[johnyrude200]

Fleetwin, you mentioned a trick for trimming the grommets, can you elaborate on this?

[fleetwin]

I will, once you get it apart and have the new grommets in hand, will be easier to understand that way.
In any event, the problem is that the top of the grommet extends over the top of the water tube, so a bit of the grommet is unsupported allowing salt build up between the grommet and exhaust tube to push the grommet inward closing up the hole. I usually just carefully trim about 1/16" off the top of the grommet to ensure it does not extend beyond the top of the water tube.
Some of the newer water tube replacements must be a little taller, because the grommets don’t extend over the top of the replacement tubes. But, I’m thinking yours is not new enough for that improvement to have been incorporated into the water tube. And, I guess if that improvement had been made to your water tube(s), you wouldn’t be having a grommet problem now!

[cajuncook1]

Johnnyrude200, Don (fleetwin )is an excellent advice resource regarding your motor as well as the other posters. I am posting these pictures and diagrams as a referral aid only and not as a distraction to his guidance. The pictures and diagrams were sourced from Leeroys ramblings website.

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