HP525 temp sensor?
 

I just launched my boat off the trailer and idled to the dock. While tying off the boat while it was idling, the overheat buzzer went off and the temp gauge went to ~220. The sensor seems to want to stay there although the motor is cooling down.

I had just replaced the water impeller and there was water coming out of the tail pipes. The odd thing is that the motor does not seem to be hot to the touch so I am wondering if it could be a faulty temp sensor?

Any thoughts?

Thanks.

Jamal

The chances of both sensors going out at the same time would be hard too believe, Was the old impeller tore in peices? Either something is blocking the cooling system Or you are sucking air some place from the water pick up area to the impeller and pushing the air bubbles to the manifold area, And the sensors are picking that up, Was this your first engine start up after the new impeller or did you start it on the trailer first?

Original impeller looked like new and yes that was the first start up after installing new impeller, fuel/oil filters, oil. I pulled out a plug from each bank and they looked good.

Are there two temp sensors on the HP525? The marina tech scanned the motor and there were a lot of fault codes, but many of them are not applicable to my boat. I think one of the faults he mentioned was that the motor was not reading the correct water and air temps.

They let the motor cool down to recheck and everything was the same again...now they say it will not even start. btw, it was in limp mode before when the temp buzzer went off.

What is going on, maybe the ECU is shot? Can one reset the ECU?

Thanks.

On the temp sensors, you have one for the coolant temp for the EFI system, one for water temp, one for the water pressure mounted in the oil cooler that reads the impeller pressure. I was thinking you might be sucking some air some place from either a bad seal/gasket at impeller or loose hose clamp of some kind, Or did you by chance for get to lower the drive down before you started the engine the first time, If so some times you will get a big air pocket between the drive and the impeller and some times it will not suck any of the water from the hose, But maybe in your case it will suck some water becouse it is in a pool of water mixed in with a air pocket giving the ECM a bad reading. I have read on another forum some guys have had to prime there impeller hose before after a new install But I never have had to, But I have had to lower the drive down then hook up the hose and then cover the low water pick up if it has one then turn on the water first before starting the engine or it will not suck any water by doing it the lazy way By hooking it all up then lower the drive and start it up. It would be hard to say why the engine will not start right now, But it does not sound like the ECM is bad at this point [IMO] Good luck with it.

Hmmm, I did have the marina swap the outdrive with a spare that I have. Air pocket's? That makes sense, I'll mention that advice to the marina guy's. Thanks.

Jamal

The tech went to start the motor today after it has been sitting all weekend and the temp gauge reads 220+ and the oil pressure gauge is pegged at 80lbs before even starting it up.

What besides the ECM would control both of those gauges?

She will idle but not accept any throttle input by stalling out when any throttle is applied?

Thanks

This can be a situation that can arise if your engine system ground is not connected or connected improperly or possible loose ground or corroded ground. check the ground connections and tighten everything up, even at the batteries themselves.
Good Luck'
Best Regards,
Ray @ Raylar

Took the boat to another dealer who is a mercury racing dealer and they finally diagnosed it to be the ECM afterall. Waiting for the new part to arrive. What would cause an ECM to go bad? Any upgrade ECM's out there?

Thanks,

Jamal

Well some times things just go out. It would be hard to tell. Their is no up grades that I know of. By the way I am just curious do you have the mercruiser smart craft system on your boat?

The HP525 is smartcraft ready but the 98 Formula is still old school electronics. Waiting for the ECM to come in.