Yup, those dumb rotors are mega bucks !

See, your buddy with the boat got off easy at the dealer.

I am going to be the VST contrarian here. I've run a VST for 22 years and am still running it. I've replaced one rubber diaphragm in it that aged out. Thats it. The VST problems people have had (specifically vapor lock) is predominant primarily due to it's location on the big blocks due to heat soak. The symptoms he has here have never been attributed to VST.

What i would like to know is can i open up the vsts and clean out the screens for preventative maintenance and not have to replace the seals? Or do the seals need replacement once you start messing with them. The boat is 22 years old and i assume its always had the vst system on it and my friend said he has had them cleaned out a few times since he has owned it. I just worry about opening them up cause the dealer is like they dont make parts for them anymore and you have to upgrade to the newer style once they break. He said there is a service bulletin on how to update them to the newer style at 1200 per unit.

update boat fixed mechanical pump and lower unit to the pump was the issue pump seized and the lower part was worn in to much so replaced both parts. Only thing that stumped me for a bit was the fuel line must have gotten to much air in it because it wouldn't prime on its own. I had to disconnect fuel line before water separator on the fuel tank and at the inlet of the vst blow into the line before water separator till some fuel came out the hose going into the vst hook it all back up and boom we have lift off. We ran it up to 4200 rpms for awhile and all is good.

thank you for help on this.

BUP just sold me new o-rings for the VST lids on mine. Previous I had taken them apart to clean them and the O-rings expanded so much they wouldn't fit once I tried to reinstall them. I searched back then on here and found a thread where someone cut a small portion out of the o-ring and super glued the ends together to make it fit properly back in the lid, it worked for me and it didn't leak. Obviously not the best solution but those o-rings are damn expensive...

In case anyone is looking for the large top o-ring by itself it is part# 25-803831

$10.00 or so. A decent amt of places keep them in stock,

http://www.boatfix.com/merc/PBullet/98/pb98_06.pdf

Full o-ring kit is part# 808500 and just over $100.00

Edit: I purchased the complete VST o-ring kit that's why I mentioned it being expensive... just wanted to clarify.

well it seems this problem has come back again, friend called me yesterday said problem started again. I cant imagine the mechanical pump went again, but i will have to check oil in lower part to see if it has any fuel in it. other than that i think it may be a vst issue and gonna have to tear into it i guess.

So I swapped vsts side to side and problem stay with same motor so I know it's not a vst problem but when the problem occurred I had the pressure gauge on it it and the pressure was dropping and bouncing all over. I have a new mechanical pump on and a new lower part for the that pump I have swapped vsts I know 100 percent fuel supply issue so I am thinking it's either the new mechanical pump went bad or pressure regulator only two things I have left really I guess any ideas.

i think i have to bring it in to get scanner hooked up to it. i have swapped vst, mechanical fuel pump, coils side to side and it always stays with the same engine. it takes a few minutes for the engine to start losing fuel pressure but its only above 3400 rpms. the pressure is good then it just drops off and bounces around till engine stalls

really need help

i was thinking its the fuel pressure regulator or ecm or map sensor maybe i suppose i could swap those side to side to see if problem moves to the other motor.