Promax?

[mercrazy]

Starts and runs fine. Takes off great, runs about 100 yards and starts slowing down like it’s running out of gas. Doesn’t miss or die. Let it idle a minute and takes off fine again for a 100 yards. Has all new fuel lines and lift pump. Primer bulb stays full. Don’t have a fuel pressure tester. Can the pump lose pressure inside the vst ?

[25two.stroke]

If the float in the vst is hanging up/needle is jacked yes.

[25two.stroke]

If the float in the vst is hanging up/needle is jacked yes.

[mercrazy]

Took the vst apart. Everything looks ok.
I put a different vst and pump on. The squirt from schrader valve seems stronger now.
Im hoping it was just a weak pump. It had been sitting for years.
Need to get a pressure tester. Hate to for 1 time use.

[Greg G]

What model Promax and what year?

[mercrazy]

1996 225.
The vst I put on is from a later year regular 200 efi.
The older promax vst requires thick spacers between vst and injector housing at top 2 bolts.
the vst I put on doesn’t require them because the injector housing on the newer engine has the spacers molded in.

[LakeFever]

Wasn’t there a psi change over the years between vst’s? Thinking maybe you need to swap your old regulator on there

[Greg G]

I think you are correct Lake

[Greg G]

To bad there was a time back in the day where a dozen boys would jump on this thread and dissect until fixed. The old S+F

[mercrazy]

Wasn’t there a psi change over the years between vst’s? Thinking maybe you need to swap your old regulator on there

What was pressure difference of those 2 ?
I need to get a pressure tester.

[LakeFever]

I think it was 3-5 psi or something like that but I can’t say for sure off the top of my head. I know this much, 3psi fuel pressure change makes a radical difference when tuning mine. I have an adjustable fpr im using to dial in the a/f and 1psi increments is very noticeable in plug reading.

As for the old S&F I think you hit the nail square there. Old. Lots of guys just aging out of the game it’s happening in the sled world too. Heck I’d say the average sled guys age is 50 now. Boats it seems even a bit older. The original s&f crowd who pioneered all the awesome content here are missed that’s for sure. trex what a character I read tons of his content. Many others too. Jay Smith is missed around here as well. Thankfully we have Chris Carson still posting though and some other very capable members. Just have to be patient sometimes because not everyone checks daily. Anyways hopefully this info is of some help

[Greg G]

Yep T-Rex was funnier than a skillet licken possum plus he had mad knowledge. He and Jay had some great one's over time for sure. Plus the Strong Island Mafia who would tell you they ran the cut with Jesus in his Superboat.

[mercrazy]

I was wrong. Both engines are 1996.
So will the regulators be the same? 96 225 promax and 96 200 efi.

[OnPad]

I think the old style vst with external fuel pump is 36-39psi and the newer style with internal pump is 34-36psi.

[mercrazy]

Update. Ran farther with different vst but still wouldn’t turn up to higher rpm. Still feels like it’s running out of gas. Should I just get a new pump?