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-   -   502s weird problem (https://www.offshoreonly.com/forums/general-q/347571-502s-weird-problem.html)

Trash 06-12-2017 10:19 PM


Originally Posted by SB (Post 4561185)
502mpi with VST. The VST is always suspect on these engine's.

Yes but not for his particular ailment. He's not experiencing vapor lock from what he's described.

NCDS2000 06-12-2017 10:50 PM

I will have to check for that behind the tstat housing i didnt see it earlier. what i did find on the problem engine is on the coil it had green build up on post and on the wire also. the other engine coil was clean. i cleaned them both cause i didnt have time to buy wires but i want to test it first.

SB 06-12-2017 10:51 PM

It can have more issues than just vapor lock. Remember, the VST is a big float bowl complete with a float/needle/seat type deal
+ with an electric pump in it....

http://www.mercruiserparts.com/Merc/...MMON/39670.gif

Revd Up 06-12-2017 10:51 PM

There is a real fine screen in the VST that can get plugged. Had a 96 Scarab that had that issue.

Griff 06-13-2017 01:34 AM

My vote is with SB and the VST having issues.

NCDS2000 06-13-2017 06:00 AM

I won't know till I get it out on the water for a good run. If it is the vst can they be removed or rebuilt or what do you do. I will have to keep a fuel pressure gauge on it I guess to see i take it?

SB 06-13-2017 06:14 AM


Originally Posted by NCDS2000 (Post 4561411)
I won't know till I get it out on the water for a good run. If it is the vst can they be removed or rebuilt or what do you do. I will have to keep a fuel pressure gauge on it I guess to see i take it?

So you saw my post and got the fuel psi tester on it ?

SB 06-13-2017 06:16 AM


Originally Posted by Griff (Post 4561395)
My vote is with SB and the VST having issues.

Another issue some have run into is the fuel pump 'lobe' in the sea water pump having issues.

NCDS2000 06-13-2017 06:21 AM


Originally Posted by SB (Post 4561414)
So you saw my post and got the fuel psi tester on it ?

i saw the post but haven't yet I was already home by then running down today to locate the Schrader valve.

mike tkach 06-13-2017 06:43 AM

my bet is vst issue,that is one of mercury marine,s biggest failures.


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