02 Yamaha F100 overheating or ?

boatnbob3

Recruit
Joined
Aug 25, 2011
Messages
2
I searched and searched, but could not find my issue posted here. Perhaps someone (Rodbolt?) can offer a suggestion. I also have the maintenance manual and scoured it as well.

HISTORY: The engine is previously owned. It came from a shop which did some head work on it. Had to weld up the passage between cylinders and mill it back down for a water/oil leak. I babied the engine for the first 20 or so hours. At the time of repair, new T-stat, timing belt, oil change, impella change.

The problem: I damaged the first impeller running the engine with the screw in water flush connector (dumb). Now that I have a service and owners manual - I know better. So, I replace the impeller and the engine runs well up to 5000 rpm, but then I get the warning buzzer around 5,200. No WOT. I back it down, shut if off (resets horn?), then let it run at low speed to cool the engine. The engine was running well at 3,500 but as I came in from about 4 hours of light running/trolling, the warning buzzer sounded again. Now I reduce the engine to 3,000 and about 10 minutes later, horn again. I backed down the RPM after achieving plane and reduce it another 500 rpm. This went on until I had to idle back for 1.5 hours with no horn.

This is how the symptoms started with the previously ruined impeller. The new impeller has about 10 hours on it. The SS housing is in its correct position - not slipped, but in its detent, the gaskets are in place and good shape. I didn't dismantle the lower portion of the water pump that is next to the oil seal. It is a bit corroded, but no passages blocked. One item on the foot shows deterioration which is where the exhaust snubber is. Underneath the snubber is a hole due to corrosion. It just looks like it is in the exhaust chamber without compromising the water intake chamber.

The SM says it could be a cylinder head issue/water pump/lower case issue/tstat/ or oil pump issue. Any suggestions. I inspected the impella and it looks good. The Tstat is very recent. I did read that you are supposed to rotate the shaft clockwise when putting the assembly back together. Could this have been my problem? I welcome all suggestions. And for Rodbolt - I did RTFM along with an exhaustive search in the threads! :)

Bob
 

mommicked

Lieutenant Commander
Joined
Dec 15, 2009
Messages
1,700
Re: 02 Yamaha F100 overheating or ?

Might be a while before rodbolt can get back to you. Some crazy ill tempered woman named Irene is comming by to see him:eek:
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,878
Re: 02 Yamaha F100 overheating or ?

Could it be getting exhaust into the water intake or outflow due to the corrosion?
 

boatnbob3

Recruit
Joined
Aug 25, 2011
Messages
2
Re: 02 Yamaha F100 overheating or ?

I pray Irene takes some Midol and settles down :) Been hit/flooded by Ivan = no fun.

Good point about the exhaust gases mixing with the water. I have an area in the exhaust chamber that has a rubber bumper. The bumper is adjacent to the water pump. Under the bumper is an area that has corroded away, allowing the bumper to push down. This very well could be the problem. I will be away from the unit for a week (had to go to work). I will fab a new piece of aluminum for that bumper backing and look closer at the portion of the waterpump that the impella sits against. I am talking about the portion that has the chambers for water to pass through. It looks a bit corroded and may not be sealing well against the gaskets. I hesitated to remove it since it is next the lower unit's sealed area.

Another suggestion that I read in the forum was in regards to the pressure valve. My mech buddy told me it is near the thermostat and can be the cause as well since at RPM, the valve allows greater water flow since the thermostat causes too much restriction. Despite supposedly only being 10 hours old (thermostat), I will be removing it for inspection and verification that it is functioning correctly with a temperature evaluation.

Thanks for your suggestions so far. May all that are in the path of Irene fair well.

Best regards,

Bob
 
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