Mercruiser 470 wont start when hot

tatias15

Recruit
Joined
Jul 30, 2013
Messages
3
I have a Mercruiser 470 that runs fine but when the engine reaches temp it usually will stall when throttled back to neutral. Wont restart until it cools, usually about 30 minutes. Mechanic said spark is fine and sprayed just a touch of starter fluid into the flame arrestor and it started and ran fine. It had an electric choke which we though was closing but found it was not. We are stumped. Any help is appreciated.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Mercruiser 470 wont start when hot

A few things to check, mainly to do with the carburetor. Next time it does it, give the throttle about half a pump to inject fuel into the manifold. That should get it going. If it does, then pull the carb, strip it and give it a thorough clean, and set it up to the book.

Another thing you might have going on is a vacuum leak. Get a can of starter fluid (and this is the ONLY use of that stuff that I recommend) and spray a little around the manifold gasket. If you get an increase in engine revs (from idle) you found a leak.

You may also be getting 'vapour lock'. How well is the engine compartment ventilated?

Chris..........
 
Last edited:

carguy001

Seaman
Joined
Jul 16, 2011
Messages
60
Re: Mercruiser 470 wont start when hot

As Chris said with the compartment temp. I insulated my fuel line and it helped mine, also rebuilt the carb. Don't over look the condition of your ignition components too. I had the same issue except mine would never stall just would not restart after in was hot, mine was several things.... For the most it is general maintaineance
 

tatias15

Recruit
Joined
Jul 30, 2013
Messages
3
Re: Mercruiser 470 wont start when hot

A few things to check, mainly to do with the carburetor. Next time it does it, give the throttle about half a pump to inject fuel into the manifold. That should get it going. If it does, then pull the carb, strip it and give it a thorough clean, and set it up to the book.

Another thing you might have going on is a vacuum leak. Get a can of starter fluid (and this is the ONLY use of that stuff that I recommend) and spray a little around the manifold gasket. If you get an increase in engine revs (from idle) you found a leak.

You may also be getting 'vapour lock'. How well is the engine compartment ventilated?

Chris..........

Everytime it has happened I have given it a little throttle and it does pump fuel into the carb however it still wouldn't start until cool. I will try the vacuum leak idea. There is not much ventilation in the engine compartment at all. just a couple vents on the rear near the stern that have what looks like dryer hose as a vent pipe to bring air in.
 

tatias15

Recruit
Joined
Jul 30, 2013
Messages
3
Re: Mercruiser 470 wont start when hot

As Chris said with the compartment temp. I insulated my fuel line and it helped mine, also rebuilt the carb. Don't over look the condition of your ignition components too. I had the same issue except mine would never stall just would not restart after in was hot, mine was several things.... For the most it is general maintaineance

What would you recommend for insulating the fuel line?
 
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