Promax 200 loss of power

[Reezenbowhunter]

I have a 1995 200 Promax, SN unknown as tag has worn off most of the number. Recently ran it a little low on fuel but not on fumes and started to sputter a bit on way back to ramp. Took it out last wknd and my son was driving and said it sputtered and chugged and he came off plane and it shut off. It started again but wouldn't get on plane. It tried to but wouldn't and would intermittently almost make it on plane but as the day went on it struggled to get barely over 2k rpm under a load and would shut off after tri g to get on plane when letting go of hot foot. Checked for spark and have it but found broke plug, found a few of those recently where center pin comes out of plug, NGK BU8H. Has had new stator, trigger, switch boxes and voltage regs/rectifiers changed last year due to a charging system issue found. Took boat out today after changing plug and it fired right up as usual and at first on trailer at ramp it felt like it had power to get on plane. Took it off trailer it would struggle to get to 2k and sounded like a fuel starvation issue and primer ball would get a little soft while trying to take off. No change when pumping ball and it was changed last year as well. Pulled fuel separator off and drained it and didn't see anything I would be concerned with as far a dirty fuel or water. Did not put fuel pressure gauge on it but it has pressure at Schrader when key is on. Fuel diaphragm was changed last year as well. Other than the spin on filter, everything was changed last year when it was rebuilt and this wasn't something coming in time, it just happened all of a sudden. I'm thinking motor lines and or filter plugged up on inside and it's not allowing fuel thru paper media. Engine will rev up without a load or in gear but when in gear it won't get above 2k but will idle fine and semi smooth for a 2 stroke. Need some ideas to look into. I'm pretty mechanically inclined but this has got me stumped a bit to not be an obvious stand out problem.

[Forkin' Crazy]

High speed on the stator out?

[Reezenbowhunter]

I would hope not. It's about a year old but anything can fail and be defective. Last time I lost a switch box it still had power but wouldn't plane out. Now it has the lean bog and is weak to 2k. I would think if high side of stator trigger as out it would at least have a little more power than now. It doesn't seem like last time. Gonna check fuel lines on motor and possibly bypass water separator to rule out plugged filter.

[rgsauger]

You'll get more high performance help over here, bud

[roadkill636]

Vst is running empty

[Merc 2.5]

If u try it again. Pump ball while try take off , what kind lectrics did u buy, I've bought switch boxes bad out of the box , not un common to buy new and have one go out in a yr , especially if it's not oem

[Reezenbowhunter]

My son was pumping the ball and it almost felt like one time it took a jump forward but then never did it again. Ball seems harder than usual at times. I took feed line off going from filter to VST last night and squeezed the ball and it felt tough. Fuel came thru but almost like a restriction. Doing lines tonight and gonna bypass the filter and check. Stator was a Sierra, trigger was CDI, boxes and rectifiers were after market. Maybe Sierra? Also gonna keep a fuel gauge on it while running tonight

[Reezenbowhunter]

UPDATE....
Took boat to water, bypassed spin on filter and ran fuel hose directly to VST from diaphragm pump. Boat ran for about 5 min or so fine on plane with no hiccups. Set boat down and tried getting back on plane, it stumbled then primer ball was squeezed and it picked up a bit but still hesitated a bit. Came back to load up and it was weak but then when loading it picked back up again and power loaded like normal. Maybe diaphragm pump? Can't think of an electrical issue now because motor stayed running and continued to build heat? Now I'm really stumped?

[Forkin' Crazy]

It is not the stator then. You can T the line and use a fuel pressure gauge and test the pulse pump. I don't have a manual on that one so I can't tell you the PSI. You can also do a flow test. Fill the VST tank up, take the line from the fuel pump to a jug and run it to see how much volume.

Can you get to the tank? If there is a check valve on the tank, you need to loose that.

[Reezenbowhunter]

My pump on this one is external from the VST, it is just a reservoir without the pump and screen inside. When I bypassed the diaphragm pump it ran for a few but then started same thing. Took pump apart and it looks good, no tears or holes. I have someone coming to DVA check the switch boxes and stator. Gonna check TPS and swap to a test ECU if need be. Did I mention I used to have a full head of hair!

[Forkin' Crazy]

The VST tank is a large float bowl, so to speak. It is a reservoir for the high pressure EFI pump. You can take it off and mount the high pressure pump in the tank like they do on all new cars. Many racers do the same. Fuel cools the pump. If you ran it dry, it may have cooked it?

[Reezenbowhunter]

My pump is external next to the VST. I can't mount it inside of it unless I changed to the other style VST. It definitely wasn't ran dry, tank was just low on fuel. There isn't any restrictions in it or the lines it's all clean. I started to think it was pulse pump when it took off while squeezing ball but then it hesitated a little then too. So it could be a switch box cutting out after it's warm. The first time it happened boat was warmed up about 10 min or so and after about a mile run it started acting up. Then I checked things and took to ramp and let it warm up about 10 min and it had power but when it came off trailer and we tried to run it stumbled like before. Took it out again after bypassing spin on filter and didn't let it warm up as long and it took right off with no hesitation at all for 2 laps around the lake which was about a mile + per lap. Came off plane and tried to take back off and it wouldn't, squeezed ball and it picked up and was able to plane out again. While running back to ramp it stumbled a bit and pretty much came off plane but idled at ramp and had enough power to power load like it first took off. Sounds like a fuel supply issue so I took pulse pump off but it was fine and electric pump has 40psi so that's why I'm a bit lost.

[flabum1017]

Run it with a fuel pressure and vacuum gauge hooked up and see if it drops pressure or has high vacuum when the problem occurs. if it drops pressure or has high vacuum, you're gonna need to go through the fuel system. Start at the tank checking the anti-siphon valve for debris, then the fuel filters, the take apart the VST and clean it out. Possible it sucked up some crud or water from the bottom of the tank.

If the pressure stays steady and the vacuum stays under 5", you have other problems such as clogged injectors or ignition miss.