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BF 130 rev limits (?) when warmed up

T

tferrio

New member
We've been to our local authorized service guy a couple times and we're not making progress too fast.

When we first put the boat in the water the engine runs great, top RPM of 5400 and generally smooth.
After some time, 15 to 30 minutes of running around we notice that the top RPM starts dropping. At first it might be 4800 and trying to go past that causes sputtering and it won’t go faster. But it runs great right up to that cut-off.
Once the top RPM starts dropping it keeps getting lower and lower over the next 15-30 minutes until we’re eventually limping back to the dock at 2000 RPM or so.

We can do it again the next day with the same sequence of events.

No indicator lights or alarms are showing up. When we turn the ignition switch on, the indicator lights (water, oil and check engine) come on for a moment like they should.

The service guy has been assuming a fuel problem. We're running off a portable tank of fresh gas to eliminate any variable about the gas in the tank. We've changed the filters and cleaned the screen at the bottom of the high pressure pump. When the problem shows up, pumping on the primer bulb does not help so we assume the low pressure pump is ok.

The water intake screens are clean and the tell-tail water stream is strong. The thermostat has been changed.

The service guy has loaned us a fuel pressure gauge and we're going to check that this weekend. (We're suspecting that won't show a problem.)

Has anyone hear seen these symptoms or have an idea of another place to look?

Thanks a lot, Tom
 
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It does sound like a fuel issue. Hopefully, the fuel gauge will prove that. Sounds like your mechanic is wise to have you watch the fuel pressure.

I am also assuming that the portable tank is well vented and you are using a different hose and bulb than normally used with your motor.

A couple of things to come to mind.

-PCV valve.
-Crankcase vent hose....hose from valve cover to intake.
-If you have changed the vapor separator vent filter (the one that runs straight up above the vapor separator)...make sure that the associated hose going up, then eventually down to an opening below, is not clogged.

If the high pressure fuel pump in not failing, then it could be a venting or vacuum issue...since it takes a little time to fail.

Of course, it could be a hose collapsing internally.

You just have to follow the evidence as you get more data.

Mike
 
Hi all, here's my update. We took it out today and ran it for over 2 hours, over 4 gallons of gas, without the problem re-occurring.

The last thing the mechanic did was replace "the screen at the bottom of the high pressure fuel pump". (Looking at the parts diagram I can't figure out what part that is, sorry. Maybe his invoice will have the part number.) But that evidently did it, was limiting gas flow after running a while.

So for purposes of this post I'm declaring the problem fixed unless I post again.

Our next step is to fill the boat gas tank (was using a portable tank) and go for a longer run.

Thanks all for reading my post. Tom
 
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