Here's an odd electrical issue

[HogansJet]

'02 Utopia w/the 240efi Merc.

Leaving the dock last weekend I noticed that my speedo was jumping all over the place...hmmmm. As I got near the channel, the overheat alarm sounds so I dropped the hook and got under the boat...the intake is clear and the speedo wheel also spins freely. Hmmm. Try a few more times and the same thing. Finally, I back her down hard...and then everything is fine for the rest of the day: Speedo works fine and no alarm. Made sure I flushed her out really well when I got home thinking maybe some junk was in the cooling system. Also changed out the water/fuel separator, although that would have been a beeping alarm, not continuous.
So, This weekend, same thing....speedo crazy...then the alarm as I'm idling away from the ramp. This time it was intermittent.
I thought maybe the overheat sensor is bad....but it seems related to the wierd speedo behavior. I can't imagine how those two circuits are related. The connections for both the speedo wire in the bilge and the overheat sensor on the engine are clean and tight. I ordered a service manual which I should have this week, but I'm hoping to get a jump on this. It has to be electrical as the problem first starts with a cold engine idling. Wierd. :ack:

Mike

 

[mmbird1]

Two cents worth

Check your fueses. Could be weak/cracked or corroded conection.Check all
molie plug together conections, grounds and so forth.:cheers:

 

[Gunsrunner]

I would always go over the earth points first. Then fuses as said above.:agree:
Then start isloating one part at a time until it stops then you know what is the cause!

 

[HogansJet]

Thanks. Going to go over everything this week. I did unplug the speedo connection and she still gets the overheat alarm on the hose after 5 minutes, so it seems those two issues are unrelated. I did find 4 wires on the front of the engine near the starter that are just dangling...and not capped off. Waiting for the service manual to arrive so I can see what these wires are.

Mike

 

[HogansJet]

'02 Utopia, 240efi Merc
I finally fixed my overheat issue...so I thought I'd share this. Actually, I had to pay a mechanic to fix it...but anyway.
Turns out, this engine will over heat on the hose after 5 or 10 minutes no matter what. The mechanic found that while running on the hose, water doesn't even fill the heads enough to reach the temp sensors and just builds a steam pocket, triggering an alarm. That's why water won't come out the bypass when on the hose at idle, but will in the water. All the cooling passages are interconnected so it can circulate, yet still not fill the heads. There are no t-stats so he removed all the lines he could, including a fitting on top of the block and just flushed everything out. Must have been sand or mud somewhere, although nothing obvious came out. Went for a run and it now runs 95*F on plane, and up to 110*F while idling. Alarm triggers around 165*F. Compression test was 125-130 all around, so no damage was done.

I don't remember running aground or being in very shallow water, but whatever, seems this engine may be prone to cooling system restrictions. We'll see.

Mike

 

[seadoosnipe]

Manual..........

The "root cause" that you describe sounds a bit weird. But if your mechanic is OEM on the boat, I guess he knows what he's talking about.

I've never heard this type situation occur on the M-2. The cooling system is considered a "total loss" cooling system. Which means, there is no water pump. The cooling system is reliant on the nozzle pressure to build water pressure on the engine.

What's weird, instead of a thermostat, the engine is set up with calibrated fittings, that create a restriction so that water pressure is great enough to fill all the upper chambers of the water jacket. At idle, the water pressure needed to fill and cool the entire water jacket of the engine is only 1/2 to 1 and 1//2 PSI., at 5800, boat on plane, the nozzle needs to generate 13 to 17 PSI to fill the water jacket. So my point is this,...... city water pressure is normally 50 to 60 PSI, with a total volume that I'm sure is greater than the volume created by the nozzle. The restrictions in the water lines of the engine, are no greater in size than your water hose. So this theory that the engine cannot run on the water hose (not filling up the water jacket), does not make logical sense to me.

As for the way the 240 EFI engine uses the temperature sensor. It's necessary to have this in working condition because the Port temperature sensor provides the ECM (electronic control module) with the information to control the fuel enrichment during warm up. The ECM is always receiving info from the sensor, but stops enrichment when engine temperature reaches 90*F. So, if the sensor is faulty, and the engine leans out while at lower speeds, then the ECM may be leaning out the engine, causing it to run hot.

I also found in the manual, that all cooling passages are interconnected by a series of hoses and internal passages, to prevent steam pockets.

You can get a pressure gage and hook it up to the top fitting of the water jacket, on the upper most part of your engine. The pressures should be within the range I first quoted in this post. Your maximum water pressure should be no more than 17 psi. Don't you think your water hose is capable of this pressure and more.

The manual goes on to list possible causes for over heating. The most common that seems to come up frequently is, a severe internal leak or restriction in the cooling water lines.

Our manual on the M-2's cooling system is very thorough and I'm hoping, that your fix to your over heating problem is fixed. Sometimes, the un-orthodoxed way of fixing something, works..........so, I hope this is the case.

But from everything I've read on your cooling system, there is no reason why you can't run your motor on the water hose without it overheating. The water hose is actually supplying more water to the engines water jacket, than the jet pump nozzle does.

One last thing. You have a water injection system at your expansion chamber. If the two cooling water lines that go to cooling your exhaust are plugged or have a low flow, this can cause your engine to over heat also.

When you get your manual, you'll see how easily this "total loss" cooling system is set up.

I find this thread very interesting. I am always busy with posts, but if I happen to miss a reply by you on this thread, please feel free to PM me to update me on your progress to this situation. I'd like to know what you find out.............:cheers: