Overheating

Post here for issues with outboard engines (i.e Yamaha 9.9) on PDQ yachts
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Marc Gershel
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Overheating

Post by Marc Gershel »

Hi Everyone, Well, I just started my engines for the first time since putting everything up for the winter. They both started up nicely and sounded good. My stbd. didn't have a good flow from the p-hole, so I tried to clear it with a wire that I have for that purpose. It helped slightly. Pretty soon that flow started to get very hot, so I shut down the engine. I pulled off the outlet hose to see if anything was blocking it, but it seemed clear. I went to re-start the engine, nothing happened. Nothing, as though the battery was diconnected. Uh-Oh What the hell did I do now. I remember a few years ago that a plastic trash bag covered the intake, the engine overheated, then shut down by itself. After letting it cool, it started right up. Is that what I have here? But even after it cooled down it's still dead. I'm not sure what to try next. HELP

Marc
SteppingStone
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engine overheat

Post by SteppingStone »

Hi Marc, It sounds like your engines overheated from a clogged cooling system. You could try vinegar through the thermostat or some "saltaway" though the cooling system. In either case, the cooling water is currently blocked and the engines shut down as a safety precaution. Roger Wood
Allezcat
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Post by Allezcat »

Hi Marc,

Do you have a spare CDI you can try? These things (CDI's) are notorious for causing symptoms just as you describe.
You could also just remove either sparkplug, connect the hi tension lead, ground the plug body, then spin the engine and look for a blue spark.
The lo-flow, warm exhaust water, are probably indications the cooling passages are beginning to "salt-up" but will not cause the engine to quit, unless the flow is completely blocked, in which case the engine will seize. See past posts on flushing.

Good Luck,
Chet / Allezcat _/) 36010
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Post by Allezcat »

Marc

I misread your engine problem symtoms. I now see that there was nothing happening, including no starter engagement. This could be caused by several things.
First check all battery cable connections. On "Distant Music" we found a corroded connection at the circuit breaker in the engine compartment caused the same problem. Another possibility is a bad starter relay. You can bypass the relay by shorting across the large terminals with a hefty screwdriver. (Be prepared for some sparks). Also check the fuse located in the rubber holder at the top of the wire junction box. (This is bypassed when you short across the start solenoid terminals) Other possibilities are the starter motor itself (bad brushes) or the neutral safety switch.(which is bypassed when you short across the start solenoid)


Chet
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Marc Gershel
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Post by Marc Gershel »

Thanks Chet, I'll check all those things. Do you know what part it is that shuts the engine down when there is overheating? I'd like to check that also.

Thanks again, Hope all is well.

Marc
Allezcat
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Post by Allezcat »

Marc,

There is no device on the Yamaha 9.9 that shuts down or throttles the engine due to overheating. There is a lo oil pressure switch that causes the CDI to bring the engine down to low power.

Regards,
Chet
Marc Gershel
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Post by Marc Gershel »

Thanks for the help folks. Everything is working fine . Relatively easy solution, with a lot of hard work thrown in. It seems that the thermostat was the culprit. but instead of trying that first (makes too much sense) I pulled the engine, dropped the lower unit,and changed the water pump impeller. The plus part of this 8-10 hour job was that I got to give the engine a really good flushing & the cooling system doesn't appear to be clogged.
The starting problem was completly unrelated, just happened at the same time. The battery cables connect to 2 studs that come through the bulkhead. These had loosened on the other side of the bulkhead, and corroded enough so that I had a 12V reading, but not enough power to cause a spark when I tried to jump the starter solenoid. I made a whole new connection that should stay tight & clean for a while.
Now I feel so good about fixing everything, I can't wait for something else to break. Yeh, right! Am I sick, or what?

Thanks, Marc Here's 2 Life
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Post by Phenix-former-owner »

Marc Gershel wrote: Now I feel so good about fixing everything, I can't wait for something else to break.
How come I get this feeling all the time? :D


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