Mercury M2 240hp Alternator and Belts

[UKGlenn]

I'm after some advice.
I have a 6 month old broken alternator belt!
I had the boat in the sea a couple of weeks ago and on the way into harbour the continuous alarm came on. Being only on tickover through the harbour and reading the M2 manual I assumed that the engine was starting to overheat and maybe we sucked up some seaweed. It was flushed fully and I have checked there was no rubbish in the impeller section.
Today I put it on the lake and the alarm came on as soon as I came off the jetty a blast of the throttle to make sure water was being forced through and then power died and the engine became really lumpy, it felt almost as if things had seized up! back to idle and seemed ok again although the alarm still on continuously. Opened up the engine compartment and found the 6 month old Mercury alternator belt snapped and in the bilge.
Alternator rotates smoothly and spins round 2-3 times with a hand spin.
My questions are these..
The manual doesn't mention charging but does the alarm come on if the alternator is faulty?
Is it normal under the guardian system for the engine to feel so lumpy - or could this be due to cylinders not firing at open throttle due to a lack of charging?
Is my Alternator dead? I can't electrically test it at the moment as I will need a new belt but should it spin better than a couple of turns?
Does anyone know the code or length for an aftermarket belt. I bought a 4pk841 from an autofactors but this was too loose.
Many thanks.

 

[Dr Honda]

Yes... if you have no output... the alarm will sound. Also... when you have an alarm, the guardian will drop RPM's.


Unfortunately, I don't know what the proper replacement is. (My 240 has a MAG, not an alternator)

 

[UKGlenn]

Thanks, I will probably replace the alternator as its the only thing I can think of that would cause the belt to snap, I read a few other posts about alternators with failing bearings but they feel good however the previous belt had stretched and was slipping and had left a lot of rubber dust around which has probably gotten in to the alternator.

Its kind of good to know the alarm comes on without a charge but I'm really worried about the lumpiness of the motor when the power cut out.. I'm hoping this was a case of a low charge in the battery without alternator charge and the coils not energising properly..

 

[Dr Honda]

There's an idler. The bearing could be bad in that too. AND... if the alternator wasn't making noise... I would blame the idler first.

 

[UKGlenn]

Ok so stripped out the alternator and had a really good look at it and the broken belt. The tensioner pulley looks ok but the pulley on the alternator has a bit of pitting and roughness to it from corrosion. The V ridges are quite rough and on closer inspection of the belt although not looking very worn there is a loss of rubber in the troughs of the grooves enough to just expose the fabric in places. It looks like the edge of the grooves on the pulley are rough enough to wear the edges of grooves on the belt enough that the ridges of the pulley have been cutting into the troughs of the belt. I have ordered a replacement alternator and put on a 4PK812 poly V belt ($10) from the autofactors to test it before splashing out for the Mercury equivalent again. I'll run it up and see if there is any rubber lost. #fingers crossed

 

[Dr Honda]

Let us know if that works out.

 

[UKGlenn]

OK so new alternator arrived and before I swapped out the old one i thought i'd run it up to see if the old one was charging which it did. The engine seemed quite rough on idle and after a short while the alarm started beeping. I noticed that the Port heads were hot enough not to hold your hand there and the starboard side was cooler. Back to forum for some ideas and have gone through previous posts about head sensors and also flushing on the trailer (its out of the water) I have back flushed the heads through the top water exits and understand now that water pressure off the hose is not enough to keep the heads cool. The motor is #0E419069 so is the newer M2. Looking at the water flow diagram it looks like the water inlet to starboard side is lower so perhaps the hose is cooling this side better if at all than the port side. But heres the question. Measuring the resistance of the two sensors i'm getting the following readings once the engine has cooled and after back flushing so assume room temperature of approx. 15-20 degrees Ctypical UK summer!)
Starboard 3.6K ohm = 50 C
Port 14k ohm = 15-20 C

Would this cause a fuel imbalance between heads and be a factor to overheating?

 

[Dr Honda]

I'm not understanding....

was this in the lake, or on the hose? If it was on the hose... you simply overheated the engine. If it was in the lake.. then you have a blockage.

Regardless... if there was a "Fuel Imbalance"... you would just melt a piston, and not feel a temp difference in the heads.

 

[UKGlenn]

The problems started on the sea coming into harbour with the alarm going off but having flushed through we put it on the lake and the alarm still went on. (i hadn't checked the belt at this stage as just assumed an overheat) It wasn't until the alarm on the lake that I noticed the broken belt. The boat is now at home and was on the hose.
Going to rip out both sensors today and test ohms in a jug of boiling water to see if at 100C if the faulty one drops low enough to be in the range of the over heating alarm as I don't really want to run the engine now. We were getting quite a nice peeing through the water vent when it was on the lake btw so I am assuming good water circulation?
Do you know what ohms the ecu sees the sensors as overheated?

 

[UKGlenn]

So... Tested both sensors in boiling water and both gave roughly the same reading equating to 100C - put both in Iced water and both gave roughly same reading equating to 0C now sat on the bench at room temperature both are reading roughly the same 14k Ohm? and not the mis match that they did the other day. Have replaced both sensors now as not confident the old one was A ok. Fingers crossed.
Ran hosed water through the top hoses and engine idling without an alarm so I'll get it back in the water in a couple of days and give it a run.

 

[Dr Honda]

I'll keep my fingers crossed for you.

 

[UKGlenn]

Update - Took boat out on sea at the weekend. Ran for two hours fine no overheating, responsive and best of all the belt didn't shred at all. Problems fixed, Thats the 4pk812 belt from the auto shop for £6. Came home and flushed through the heads by disconnecting the pee hole hose and connecting the tap water hose on. :thumbsup:

 

[jasguild]

Came home and flushed through the heads by disconnecting the pee hole hose and connecting the tap water hose on. :thumbsup:

are you saying you flushed backwards into the system?

 

[UKGlenn]

are you saying you flushed backwards into the system?

Yes, although I have quite good water pressure at home it still isnt enough to fill the heads with water when using the flush attachment which is great for flushing the exhaust and impeller. So i have been going straight into the top of the heads and through the whole engine via the 3 way connector at the top of the Port head.

 

[Dr Honda]

Yes, although I have quite good water pressure at home it still isnt enough to fill the heads with water when using the flush attachment which is great for flushing the exhaust and impeller. So i have been going straight into the top of the heads and through the whole engine via the 3 way connector at the top of the Port head.

I've thought about doing the same thing. I've found VERY FEW garden hoses that have enough pressure and volume to actually cool a sportjet via the original flush port. The reason is... the majority of the water simply goes out the pressure port in the pump.


If you get a chance... post up a pic of what you did. (how you hooked it up)

 

[jasguild]

Yes please post a pic.

So when you do this backway flush where does the water exit?

This sounds like a great idea but cant help wonder if this is safe for your engine ie water going in the opposite direction than it was designed to move.

 

[UKGlenn]

Yes please post a pic.

So when you do this backway flush where does the water exit?

This sounds like a great idea but cant help wonder if this is safe for your engine ie water going in the opposite direction than it was designed to move.

Update...
OK. So my thinking behind this. The pee hole vents the top of the heads meaning the pressure of the water is already in the water chambers normally so back hosing should make no difference. The water drains down through the bottom grate as normal. So I've towed the boat to Spain and been playing in the Mediterranean Sea for 2 weeks been coming into the beach and on 2 occasions one after stop starting trying to get a wake board going it wouldn't start and once after loads of donuts. Engine seems hot and lots of fuel vapour in the throttle chamber? Seems to be flooding. 15 minutes rest and fired up again. Worried I'd sucked sand or something up, back to the marina where there's a hose and holding the rubber hose direct on to the pee hole gave it a quick back flush. It was a bit spray,ey but I was already wet so no problem. Nothing but water came out but my mind was at rest. Yesterday though pulled the boat out the ramp and back to the holiday home went to turn the isolator off and noticed the fuel pump was still running with no key in the ignition. What's going on? Dodgy key switch?

 

[Dr Honda]

Which pump was running?? The square lift pump on the side of the engine (ticking sound) or the high pressure pump in the vapor tank? (A whirring sound)


If it's the Lift pump... the relay mounted next to it may be bad. OR... the key switch.

If it's the high pressure pump... then the ECU may be shorted, or the ground wire from the pump is shorted. (The ECU controls the ground)

 

[UKGlenn]

Yeah the square pump on the side. Only intermittently. I'll check things out.

 

[jasguild]

UKGlenn

Please remember the pic. I would love to start doing a reverse flush on mine as well. It does not sound like your current problems has anything to do with your reverse flush invention, correct?

 

[UKGlenn]

Just back from 2 weeks in sunny Spain and as mentioned above wanted to do a quick flush on the Marina ramp so just held the ramp hose onto the external pee hole.
Here is were I've been doing the head flushes inside the engine.
I've ran the engine for a short while like this... ( Yellow hose is the water hose attached using the jubilee clip from the pee hole hose) and the heads are cooled so well they only just warm up.

 

[Dr Honda]

Cool.


I've thought about mounting a second flush fitting to my hull, to get some cooling into the engine, while in the driveway.

 

[jasguild]

Are you disconnecting the hose to the pee hole everytime you want to flush and then reconnecting when you are done?

 

[jasguild]

I have been using a small high powered hose nozzle to spray up the pee hole with my garden hose. The stream is small but high pressure so I dont get wet and I flush it backwards with saltaway until i see it coming from through the pump.

 

[UKGlenn]

Yes, disconnecting the pee hose each time. I was also thinking of that Dr Honda just need to do some looking round for some suitable fittings.