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Hot Restart probelm

E

Eaton Beiver

Member
So I have the infamous "Hot Restart" problem on an otherwise well-running M440. After running for a while, and getting warmed up (Ex: Pulling skiers for 30 minutes), if I shut it down for a few minutes, it fires right up. But if I shut it down for 10 or 15 minutes, it acts like its vapor-locked and flooded at the same time. It will always restart, but it take a bunch of cranking, and false starts and excessive drama. (It alarms the passengers...) I believe this is simply the "Hot Restart" problem that is somewhat common. It seems like it's heat from the engine, causing fuel to boil in the lines, possibly forcing fuel into the manifold while not running.

So my question:

Do any of you know of a solution to prevent hot-restart problems with 40 year old inboard engines?
 
Yup: an electric fuel pump.

Can you open the hatch(s) to let the heat out? After a hot run, I used to pull the doghouse back on my old Bayliner with the infamously bad, hot restarting 4 cylinder motor (with its carb sitting atop the exhaust manifold).

Jeff
 
A heat resistant carb spacer (you can get plastic ones from Summit or Jegs) can help somewhat, but the electric fuel pump with fix it forever.
 
Yeah…..it’s most likely the heat soak issue that you suspect. If it is, there are a couple of things you might try/look into.

1) If you’ve got copper lines, you may want to replace them with marine-grade rubber line (at least in close-to-the-engine areas like from the fuel pump to the carb). Being a better conductor, copper will heat up more than the thicker rubber line.

2) Its worth checking fuel pressure. Low(er) pressure can make hot restarts that much harder.

3) You may want to try altering your shut-downs to see if that helps. You mention skiing…….which obviously involves a lot of heavy throttle driving and is often accompanied by quick shut-downs. Depending on how quick the shut-downs are, you can end up with more unburned fuel in the carb/intake than you might after a gradual transition to idle speed. If, by chance, you find yourself shutting down quickly after that heavy throttle driving, might want to try holding an idle for a minute or so before killing it.

Maybe one or a combination of those things will help.
 
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The cool off that bogdenz recommends is prudent. the other 'trick' is to open the throttle at least half way and then hit the key. As soon as it starts, reduce the rpm to ~ 1000 rpm for about a minute before going to idle.
 
Interesting point Bogdenz; I did recently replace older rubber fuel lines with..... in fact.... you guessed it.....copper lines. And they certainly do feel warm enough to boil gas, after heat soak.
Thanks for the tips, and they'll be tried this weekend.
 
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