2006 200 Select overheating - Merc 5.0 MPI (305ci)

[scoflaw]

A PSI sensor/gauge on a Alpha?

Smartcraft right? Would the drive matter?

 

[Coconuts]

Ya, I have the smartcraft guage - digital - it shows water temp along with water PSI. I have no poppet valve.

 

[techmitch]

Smartcraft right? Would the drive matter?

Just never heard of it on a boat with an alpha drive.

 

[Scott215]

My 2006 5.0 MPI has smartcraft,I just don't have gauges to veiw it. Alpha 1 gen 2

 

[Coconuts]

well - I'm hoping a new thermostat will fix it - ordered and will be here sunday. Still don't understand how revving up in neutral helps cool temps - almost like there's an internal water pump on the pully system that moves water???? no way the impeller on the lower outdrive moves when I rev the engine... unless I'm totally loosing it...

 

[Espos4]

You do have 2 “water pumps” with that engine/outdrive assembly.

One in the drive and The other one is what you might refer to as a conventional water pump on an automotive application, called a circulating pump on your boat engine.

Could be that the impeller on the circulating pump is corroded and it’s not moving enough water at the lower speeds.

 

[Coconuts]

ah yes - I figured as much. I'm guessing that pump is messed up... will look to replace that impeller too!

 

[scoflaw]

That would be a long shot, that impellor is corrosion proof. Yes that is the circulating pump.

 

[Coconuts]

That would be a long shot, that impellor is corrosion proof. Yes that is the circulating pump.

but it would explain why increase in RPMS in neutral increases water pressure just a bit.

 

[Lazy Daze]

but it would explain why increase in RPMS in neutral increases water pressure just a bit.

No, it would not. The PSI sensor is well before (it's on the oil cooler) the circulating pump on the front of the engine.

And... there is no impeller to replace in the circ pump. You do the whole thing. It's much more likely to have an issue with the raw water pump (whether the impeller, the plate/housing or a previously broken vane clogging something) than the circ pump.

 

[Coconuts]

ok - if that's the case, can someone explain the basics of how this works then - does the raw water pump impeller (in the lower outdrive) actually spin faster when RPMs are increased the the boat is in neutral?

 

[Lazy Daze]

ok - if that's the case, can someone explain the basics of how this works then - does the raw water pump impeller (in the lower outdrive) actually spin faster when RPMs are increased the the boat is in neutral?

It spins relative to RPM - gear/neutral is irrelevant.

It might be a good idea for you to purchase a Mercruiser service manual and read through it to gain some knowledge on marine engines before wrenching on them. It's a worthy investment

 

[Scott215]

That's a good idea, everyone should have one

 

[Scott215]

Problem most likely in the outdrive impeller or housing

 

[Coconuts]

ya - agree with you Scott - have a brand new impeller kit and the Merc Service manual... I've had outdrive off before and I think something got messed up putting it back together - it's a PITA to work on...

 

[Nater Potater]

Looking at the cooling diagram, check out #2 Check Valve, then the oil cooler (not numbered) immediately downstream of that, for chunks of old impeller vanes. Both are notorious for becoming plugged if the PO lunched the impeller.

 

[Lazy Daze]

ya - agree with you Scott - have a brand new impeller kit and the Merc Service manual... I've had outdrive off before and I think something got messed up putting it back together - it's a PITA to work on...

Just drop the lower - that only takes about 20 minutes.

 

[Scott215]

If you pack too much grease it won't pump enough water

 

[Scott215]

My boat runs 170 to 175 if my gauge is rite. This weekend it was a tick over 170 but if I brought it up to 1000 rpm the temp would go down but it has done this since I bought it and never gets to 180 or the alarm

 

[Wanderer 290]

There is a plastic tube from the water pump that slides over a copper tube in the upper housing that if not properly joined will significantly reduce water flow to the engine. Dropping the lower will reveal if the installation was correct.