yammi overheat alarm!!!!!

[iltfish]

I need some help here guys! I have a 2520MVSC with a single Yam S200TXRX (carbed 6 cyl). Running in yesterday at about 4600rpms (flat day), the overheat alarm went off. Engine came back to about 2000rpms (normal). I turned my head to the engine and saw smoke coming out the exhaust and also water streaming from the pisser (normal). I immediately shut down the engine and got towed in. Back at the dock, I pulled the Thermostats thinking that one stuck but they both looked ok. I then hooked up a hose to the flush adapter and ensured that water was getting to the T-Stats housing.As I keep spares on the boat, I replaced both T-Stats as a precaution. I then run the engine in neutral for about 30 mins varying rpm between 700 (idle) and 2800. I don't want to run it at high rpms in neutral. I am planning on running it for a test run on this Thursday.
Is there anything else that I should be looking for here?
That smoke out the exhaust has me worried, but it only did it when the overheat warning was tripped. It never did it when I ran the engine later in the slip.

 

[DaleH]

I then run the engine in neutral for about 30 mins varying rpm between 700 (idle) and 2800. I don't want to run it at high rpms in neutral.slip.

2800 RPMs in neutral?!?! OMG, without a LOAD on the motor that's enough RPMs to throw a top-end bearing housing! NEVER, ever run an OB that high in neutral intentionally ... never intentionally exceed sustained RPMs of 1600 or so in neutral - ever.

You need to check your poppitts, which are a notorious problem part on Yams and overheating issues - as well as your impeller. The heart and soul of your motor's cooling system starts with the impeller, and without verifying that, you're just throwing parts, time, and $$ at it.

When was the last time you had a full water pump service, to include a full waterpump kit (key, gaskets, o-rings, wear plate, housing (possibly) and impeller), poppitts, and thermostats?

 

[iltfish]

I only throttled it to 2800 and right back down.

 

[iltfish]

Full water pump service was done this spring

 

[windknotnc]

I have had an overheat alarm before even when the motor tell tale is running. There is an O-ring gasket on the bottom of the waterpump housing and if it is leaking, water escapes and will cause the engine to overheat. Usually you notice this immediately after a waterpump service, but you never know.