2008 Hpdi 200 rpm loss?

[walker07]

I’ve got a 2008 Hpdi 200 on a Skeeter Zx200. Recently picked up a Tempest 25p, and trying some jackplate adjustments. I’ve ran across a problem on the last 2 trips. The boat tops out at 63mph at around 5800rpms.(which is about where I’d like to be)

Here’s the problem.... After planning off and reaching top end, the boat loses around 800rpms after .5-1 mile. I can stop wait a minute, and get the exact same results?? It’s got me puzzled, and looking for opinions...

[ford4wd08]

I've been helping out with his motor.

It appears to be a warm engine issue. Cold engine, no problem, you can get to 5800 rpms, once it warms up it struggles to get to 5200 rpm. I think we are experiencing an intermittent miss that is happening after a "heat soak".

I'm not a Yamaha or a HPDI guy, but we have replaced all the water fuel separating filter in the bilge, the filter on the engine in the clear housing, and the expensive filter after the VST. Also a new set of plugs.
It is hard to tell if this is a fuel issue or not.

My only other thoughts maybe a coil is failing intermittently, but not sure how to confirm that?

I know 2 cylinders aren't firing at neutral while on idle.

Here is a quick (horrible) video of the issue. This is WOT and full trim and you can just see the RPM's fall back.



Any one had any similar issues?

[ifishinxs]

Just spit ballin here. Have you checked the lift pumps? and primer bulb.

[ford4wd08]

Just spit ballin here. Have you checked the lift pumps? and primer bulb.

The lift pump is in the VST right?

That's next on the list I think. Primer bulb seems to be ok, it pumps up firm.

[PearlMistZ521C]

Does it have the grey fuel lines under the cowling?

[ford4wd08]

Does it have the grey fuel lines under the cowling?

I'll have to confirm.

Are grey fuel lines bad? Do they deteriorate? I do know 100% gas is used almost religiously.

[ford4wd08]

Found this thread searching around.....

http://www.bbcboards.net/showthread.php?t=262406

Not sure if this is worth looking into or not.

He is not having the symptoms described at end.

[ifishinxs]

The lift pump is in the VST right?

That's next on the list I think. Primer bulb seems to be ok, it pumps up firm.

Lift pumps are on the side of the motor. if they are bad you will not get the fuel needed to the VST tank. The bulb would pump up but could still restrict fuel flow. If the bulb is more than a few years old replace it.

Look up HPDI lift pumps. Pretty easy to check and replace.

[ford4wd08]

Lift pumps are on the side of the motor. if they are bad you will not get the fuel needed to the VST tank. The bulb would pump up but could still restrict fuel flow. If the bulb is more than a few years old replace it.

Look up HPDI lift pumps. Pretty easy to check and replace.

An easy check for this would be to pump the bulb while trying to make a run right? If it improves, the lift pump is failing?

[Bahala]

An easy check for this would be to pump the bulb while trying to make a run right? If it improves, the lift pump is failing?

If I remember correctly, you remove the bolts from the pump, pump the primer bulb, and look for any fuel leakage around the rubber diaphragm. There are some old threads here that detail the procedure.

The two cylinders not firing while in neutral is how the HPDI works.

[bayouXpress]

i have the same boat and motor and the loss of rpm is a nightmare to figure out. But i'm going to say that it is not an intermittent coil issue. I had a coil issue but the drop in rpms is sudden and after a couple seconds would come back just as fast as I lost it.

With it slowly going down thats a tough one, but I've had that several times. Sometimes it would happen a couple times a trip then just clear up by itself. Sometimes it would not allow me to get pass a certain low rpm. Then I could go for months and it not happened. Never could pinpoint the exact problem, but I felt like i did everything. Swapped all 10 filters including basket filters, got injectors clean, drained tank, changed plugs, new water/fuel seperator, you name it. The first time it happened one of those or the combination of them worked. After that i had that coil issue but as I said that was a sharp instant drop in rpms.

I would first get the injectors professionally cleaned. I would recommend that to anyone with an HPDI of any size. Good luck.