RPM lost at 2800 PCM Pro Boss GT40 Ski Nautique 96

I'm reading this post as I have the engine stumble when above 2800 rpm issue... my boat runs great otherwise and starts right up.

So regarding the 2 sensors, oil and water which are tan/black wires,, if I disconnect both and leave the circuits open, this will send a "good" message to the ECM that systems are ok and boat will run correctly. Conversely, connecting either or both wires to ground would put the system in LIMP mode. Is that correct?

Oh man 🙈🙈🙈 all clear thx for the explanation im far away of bad pressure 😂😂😂

Im not sure about those pressure numbers. In manual there is written 5psi but my gauge shows much more than 5 so i thaught it has to be on 50 then.




Or is it really meant to have 5psi? So then im far away of this number 🙈😅 wich would be perfect. Sorry for my newbie questions 😅

The picture shows a little over 40 psi , did you mean to say 40 or 4 ?

Edit I think you're saying the picture is at 3300 rpm and you have a little over 40 psi but at idle it drops to 4 or so. That's on the low side at idle

If pressure is less than 5 psi and you hit about 2700 to 2800 rpm, you'll go into limp mode.

You don't say whether that oil pressure is with cold oil or warm oil or what speed the engine is running, but that pressure is good and nothing to really worry about especially if it's warm oil and you're on plane at cruising speed.

Whatever difference you see could be due to differences between the new gauges vs old gauges.

KENO wrote: Sounds like the switch is the problem, just wanted to verify what you did. By the way, your English is much better than I could speak any of those 4 official languages of Switzerland

Google is my friend but yeah i almost only speak swissgerman, a bit french and can understand 1% italian 😅🙌 70% are talking swiss german here

KENO wrote: This may be a silly question Basler, but would the engine act up in neutral before you disconnected the wires or was it only under load ? The reason I ask is because in neutral you can rev an engine real easily with very little fuel demand and maybe you think the problem is solved and then when you get on the water you could have the same issue show up. If you don't know the answer to the first question, I'd try reving it up in neutral with the wires connected again and see what happens. I'd hate for you to think it's all figured out and then find out it's really a fuel supply issue when you run it under load

The problem shows also in neutral we did reconnect the sensor and also in neutral it stucks on 2800 when disconnected 3000RPM there is no issue with the rpm limitation. Im sure the sensor is defective. Yes would be hard this would not be the solution but with this im sure (hope) this will work with a new one 😅

This may be a silly question Basler, but would the engine act up in neutral before you disconnected the wires or was it only under load ?

The reason I ask is because in neutral you can rev an engine real easily with very little fuel demand and maybe you think the problem is solved and then when you get on the water you could have the same issue show up.

If you don't know the answer to the first question, I'd try reving it up in neutral with the wires connected again and see what happens.

I'd hate for you to think it's all figured out and then find out it's really a fuel supply issue when you run it under load

If the boat runs good with the switch or switches disconnected and your gauge readings are normal, I'd use the boat just like you always have while the parts are on order.

Before the Protec engines and the GT40's came along the engines
didn't have this "additional protection" feature

Some people might call it a nuisance that causes more problems than it prevents especially if you pay some attention to the gauges

Basler wrote: Checked now with the wire disconnection. I disconnected both water temp and oil pressure switch. It runs over 2800rpm when i accelerate in neutral now. Looks like i need to replace the oil pressure switch by the way i will change also the temp switch just to be sure its all good. When i disconnected the oil pressure switch, the gauge in the cockpit still shows the psi information. Is it possible that the gauge gets separate psi informations?

Here's a picture courtesy of Lewy

He has the switch that puts you into limp (SLOW) mode circled in yellow. That switch has only one function in life......to tell the computer to put the engine into limp mode if it thinks oil pressure is less than 5 PSI.(and the computer puts the engine in limp mode and turns on the check engine light unless it's burned out)

Right next to it in the picture with the light blue wire hooked to it is the oil pressure sending unit whose only function is life is to feed a signal to the pressure gauge on the dash.

Two totally different pieces of equipment, they both sense from the same point with a tee in the line.

If the switch goes bad, it'll put you in limp mode even though oil pressure is normal.

You should see normal pressure on the dash gauge before cruisin' around with the switch disconnected

Checked now with the wire disconnection. I disconnected both water temp and oil pressure switch. It runs over 2800rpm when i accelerate in neutral now. Looks like i need to replace the oil pressure switch by the way i will change also the temp switch just to be sure its all good. When i disconnected the oil pressure switch, the gauge in the cockpit still shows the psi information. Is it possible that the gauge gets separate psi informations?

Basler wrote: where can i connect the fuel pressure gauge?

There's a test connection at the front of the fuel rail usually referred to as a Schrader valve.

You need a test rig with the right adapter to screw on to the Schrader valve.

The valve resembles an oversized valve stem on a car tire, bike tire etc..

Like MrMcD said, "it costs zero to check" unless you have to buy the test rig, then the cost goes up some    But it's a handy tool to have

The engine light does not light up. But its impossible to go over 2800RPM everytime i try goes back to about 2600 and everything is going fine till 2800 and if i go above the same problem repeats. I go on the river in a few hours and will try to disconnect the temp and oil switch. Lets see what happens 😅 where can i connect the fuel pressure gauge?

MrMcD wrote: When my GT40 went into limp mode 5 years ago it did not run smoothly. It was very rough. I got back to the dock with it stuttering and without enough power to get up on plane with an empty boat, only 2 people on board.   It sounded like it was running on 4 cylinders. Good advice on this forum had me replace both the Coolant and Oil Pressure sending units and the boat has never stumbled since. The boat was 19 years old so it did not bother me to replace them as maintenance. It seems to me there are 2 coolant sensors? I also replaced the Thermostat at this time. One of these cured my issue but I don't know which as I did them all at once wanting to get back on the water.

The engine runs really smooth and also got enough power but over 2800rpm it stucks. Thanks for your feedback hope can solve the problem soon.

When my GT40 went into limp mode 5 years ago it did not run smoothly. It was very rough.
I got back to the dock with it stuttering and without enough power to get up on plane with an empty boat, only 2 people on board.   It sounded like it was running on 4 cylinders.

Good advice on this forum had me replace both the Coolant and Oil Pressure sending units and the boat has never stumbled since. The boat was 19 years old so it did not bother me to replace them as maintenance. It seems to me there are 2 coolant sensors?
I also replaced the Thermostat at this time. One of these cured my issue but I don't know which as I did them all at once wanting to get back on the water.