5hp honda stalls when hot

gmtex

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I have a 1984 5hp that dies and wont' restart when hot. I have checked the exhaust manifold under the cylinder head, and it looks solid (no holes or rust). Do these motors have a safety feature that kills the motor if overheated? I noticed less water from the 'pee-hole' and today checked the impeller- it is toast so I've ordered a new one. Could this be all there is to my motor quitting. If this is not likely, then is there a way to check the electronic ignition component?

thanks in advance to all your suggestions
 

Sea Rider

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At which trottle settting does the engine dies ? Electrical failures misbehavings are difficult to troubleshoot, cools down and engine starts again to fail when heat builds up on them and so on eternally. If engine has had an overheat cond while running with shot impeller will need to re torque head gasket to factory specs. But being a 30 year oldie would change it for a new one, take advantage to decarbon combustiob chamber and clean all internal water paths as to work immaculate clean with new impeller.

Happy Boating
 

gmtex

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It will die at any throttle setting, though I rarely run it at WOT. Seems to die more when low speed or idle. I cleaned the carb, jets, etc and still have the problem.
 

Sea Rider

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Could be a Ignition Coil, CD failure or shot head gasket ?

Happy Boating
 

MattFL

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When it dies, immediately check for spark. If there's no spark then you have an electrical problem.
 

Sea Rider

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Is that a compact one piece ignition coil/cd unit or separate electrical components ?

Happy Boating
 

gmtex

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thanks for the suggestions; I just got new impeller and thermostat in (old T-stat was stuck open and bent). Engine starts and runs fine, great stream of water from pee-hole at first, but after 5min stream is much less (due to t-stat opening? or not). I did get impeller in proper direction.

The ignition coil/cd unit appears to be a small black rectangular unit just behind the flywheel; I see something else (round black unit) down near shaft on back.

Also, head temp by infrared device is close to 300deg F when running- does this sound ok?

I haven't run it longer to see if it will die, I will check for spark if it dies.

thanks for any input,

greg
 

Sea Rider

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Go full throttle and check if engine dies under load, Was that engine used on salt water, if, so, was if well flushed after outing ? Assume you are testing engine in open water or with muffs, barrel ?

Happy Boating
 

pvanv

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300F is way too hot. 150 is more like normal. Probably crud in cooling passages. Does it still die when hot? Will need to de-crud the passageways. Possibly with a LOT of vinegar... or salt-away... or pull head and start scraping. But... on a 30 year oldie, the head bolts may snap.
 

gmtex

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I'm testing it in a barrel. Was always used fresh water on sailboat, as far as I know. I have not run it full throttle as I was worried about the heat and didn't want to overheat it, so I shut it down. I'm afraid to let it run until it dies since it seems so hot. I suspect the high heat may be crud in cooling passages, and after I get that taken care of then I can see if it is still dying when I run it 15 min or more.
 

MattFL

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What part of the power head are you checking the temp on? If you're near the exhaust manifold it's going to be hotter than the cylinder and head. Check the cylinder and head if you can.

Also when it dies, is it locked up?
 

Sea Rider

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Is that a 2 or 4 strokes engine ? Engine has an incorporated fuel tank inside cowl or an aux tank ?

You should never run an engine on a barrel for extended time periods, you're actually cooling engine with hot water and will overheat engine. To cool engine properly will need a hose providing fresh water inside barrel and a faucett at lower barrel releasing hot water out. That's were your overheating probably comes from ? For extended idle/fast idle neutral testing much better are muffs. Ideal is at open water at load.

OTOH if overheating on barrel and being such an oldie, cylinder head being extremely compressed, dried out, will allow water entering combustion chamber and engine shutting down. There's always corrotion between head gasket, crankcase and cylinder head. Is it possible to test the engine on open water and at full throttle, if engine dies real fast you could have already a shot cylinder gasket or a faulty IG/CD unit.

Happy Boating
 
Last edited:

gmtex

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MattFL: I checked it on the cylinder head. Does not lock up when it dies.

Sea Rider, it is a 4 stroke; I'll try putting muffs on it (open water too far away to make testing easy).

Will checking for spark when it dies help identify if IG/CD unit is bad?
 

MattFL

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Checking for spark won't tell you exactly which part is bad, but really narrows it down. If there's no spark then you know the problem is electrical and that gives you a solid starting point.

Theses smaller motors can run in a barrel for a long time before the water gets hot. Either check the temp occasionally with your hand, or just let the hose run in the barrel and it will stay cool.
 

Sea Rider

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Usually there's only 2 possible conditions. IG/CD as a compact unit is shot, won't produce spark no more or you have an intermitent heat related issue. Works ok when cold, doesn't work when hot and the cycle goes on eternally. Assume you have other electrical components besides IG / CD, right ? If so, could be with electrical issues too. Finding out which one is the culprit is the big dilemma.

Happy Boating
 
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