1997 mpi vapor lock problem (help)

rssteiny · 04-06-2008, 04:54 PM

anyone ever had a 1997 502 mpi that vapor locks when ideling for a period of time, this is the year before they put a fuel cooler on them in 1998 , if so what can be done to cure the problem. i have a freind that has this problem and he talked to another guy with same year set up that also does it.

his problem occurs after short idle time 3 to 5 mins coming out of no-wake zone. Then trying to come up on plane one of my motors will shut off. Then after a short time it will start and be fine???

thanks

Ted G · 04-06-2008, 05:24 PM

One way that might help is to plumb the fuel pressure return hose to the tank instead of to the VST tank. In order to keep the MEFI system compact Mercruiser chose to recirculate fuel back to the VST tank instead of the tank. When the fuel keep recirculating to the VST it keeps heating up in there and eventually vaporizes. By running that hose back to the tank you will constantly be bringing cool fuel up from the tank. He could also add a fuel cooler in the fuel line before the mechanical pump, this would also help.

obnoxus · 04-06-2008, 06:11 PM

There is a bulliten for your engine that adds an electric booster pump.

This was common in the models with out the mechanical sea mounted pump.

rssteiny · 04-07-2008, 07:34 AM

Quote:

Originally Posted by obnoxus

There is a bulliten for your engine that adds an electric booster pump.

This was common in the models with out the mechanical sea mounted pump.

where can i find this bulliten.

thx

satisfactionII · 04-07-2008, 07:56 AM

I get the same problem on my 1996 Scarab sometimes. It usually happens after idleing thru a long no wake zone. Probably happens two or three times a year. It sucks when it happens. I would like to know where the bulletin is as well.

Inspector · 04-07-2008, 08:22 AM

Hi, I have two 1997 502 MPIs and have had vapor lock problems only after shutting the engines off for an hour or so (never while at idle). I posted the issue here last year and one of the suggestions was to add Marvel Mystery Oil to the fuel as it raises the boiling point of the fuel. This worked for me... As far as the adding an in line electric booster pump, that applied to engines which do not have the water pump mounted mechanical fuel pump (my 97s have the mechanical pumps).
Good luck...

MarineShopInc · 04-07-2008, 10:41 AM

Vapor Locking Kit p.n. 862264A4 is what is used to solve the problem. Jim

rssteiny · 04-07-2008, 05:31 PM

Thanks Guys For The Info.

go propless · 04-07-2008, 07:21 PM

I have the bulletin. just got it today. if you want a copy PM me with a fax # and I will sent it over to you. This bulletin covers alot of the problems we are having and some ways to fix it.

rssteiny · 07-28-2008, 06:00 PM

this happened again this past weekend to my buddys boat, anyone ever fix the problem once and for all.