470 Stalls At Throttle After Resting

terrius

Recruit
Joined
Aug 12, 2010
Messages
4
Bought an 81 Sea Ray runabout last summer as my "first boat" to take the kids out on the lake. It has the infamous 470. I do not know much about the history, but I bought it at a local Marina who had it on consignment. The Marina was very helpful and showed me all the ins and outs (this being my first boat) and they claimed to have compression tested the motor, but they didn't water test it (it was rather cheap as it needs some interior work so I doubt anything was done other than putting it on the lot). I ran it most of last summer without touching a thing on the motor. It was running a little hot (never in the red, but got to within about 10% of it one hot day while towing a tube), so over the winter I took the outdrive off and replaced the water impellar and housing. I also replaced the thermostat, acid washed the 4" exchanger, and replaced the fuel filter. All of the parts actually looked Ok so I think the previous owner took care of it (although the tstat housing had blue goo that had hardened partially blocking the water flow because whomever worked on it last used too much gasket stuff).

Anyways, on to my problem, the engine fires up, idles and purrs perfectly when cold and runs great UNTIL I shut it off. Once I shut if off to swim/eat/etc for 30 minutes or so, it starts back up fine, however, when I take it up to mid throttle to plane it out on the return trip, sometimes it will stall / hesitate / die. I first thought it was vapor lock, however, yesterday I was very careful not to let it get too hot and also let it idle for 5 minutes before shutting it off. Again, started fine, got up to speed fine, then about 2 minutes later it tried to stall out. I could touch / grab the metal fuel line between the carb and pump and it only felt warm, not hot. I touched the carb housing and just warm, not hot. When it stalls, if I pump the throttle a few times it will come back to life so I'm thinking it's not getting fuel. If it does die, I can usually get it restarted rather easily.

So, if it's vapor lock, why does it only stall after shutting if off and not stall when the engine gets very hot beforehand? If it's not vapor lock, what else could it be? I would say fuel pump, but again, it runs perfect until I shut it off. I'm thinking maybe bad gas as I think it does it most often right after I fill up the tank, but again, wouldn't that cause it to run bad before I shut it off too?

Any ideas on what else to check?
 

dn010

Petty Officer 1st Class
Joined
Oct 16, 2010
Messages
301
Re: 470 Stalls At Throttle After Resting

Rebuild the carb.
 

terrius

Recruit
Joined
Aug 12, 2010
Messages
4
Re: 470 Stalls At Throttle After Resting

I'm curious, is it typical for the carb to foul only after being shut off? It only fouls after I shut it down and sit for a few, never before.
 

dry dock

Seaman Apprentice
Joined
Oct 12, 2006
Messages
44
Re: 470 Stalls At Throttle After Resting

welcom to the 470 club had the same thing happen switched to super unledded and a eletric fuel pump. seemed to solve the fuel prolblem. good luck...
 

dn010

Petty Officer 1st Class
Joined
Oct 16, 2010
Messages
301
Re: 470 Stalls At Throttle After Resting

It is a good place to start, especially if you are unsure of the last time it was rebuilt. Mine was the same way - ran fine, was good to go when it was cool but when it was warmed up - it would give me a hard time getting through 2K RPMs and then again at 4K RPMs. Rebuilt the carburetor and it has been fine since, although I need to readjust my timing to the updated specs. Dirt gets mixed up in the carb while fuel is being shot into it, and settles after it is shut down, passages might get clogged, etc. Definitely get some new gas in there as well, and when is the last time the filters have been changed? Do you have a fuel/water separator - changed that if so? Rule these things out now before you're trying to rule them out - on the water.
 
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