Mercruiser smoking/overheating
 

First things first- this is my forst post. I have really enjoyed learning from browsing here. I am a happy Mariah owner here in Minnesota. I rarely see other Mariahs on the lake, and that I like.
Here is what we have;
1996 Davanti 225 with Mercruiser Bravo three outdrive
Just got her back in the water today for the first time this season.
Last fall went through regular winterizing procedure from my boat shop (very trusted long running local boat shop)
Added 20 gallons of fresh gas, charged batteries etc...
Launched her in the lake, started fine idled fine. Idled fine for 10 minutes, I let her warm up and eased onto the thorttle to burn some gas. Strange sounds, reminded me of a motorcycle when the exhaust headers are not totally tight and there is some exhaust blow-by, accompanied by some smoke. Shut engine off and saw smoking from side of engine under where oil is added. I figured some oil was spilled during filling, and decided to start back up thinking it would burn off. No biggie.
Started to throttle up again and the sound came back, enough smoke started that the engine killed. Opened the hatch to lots of white smoke, and a sizzling sound. Thinking the engine was on fire (and since I could not see) hit it with the fire extingusher. and threw a gallon of water onto the engine. Smoke eventually subsided, water evaporated off engine. Started her back up and idled back to dock (300 yards) got hot again and started smoking again. Threw on more water, left the hach open for an hour for heat to dissapate. End of story.
I've got a call in to my mechanic.
Just curious about any ideas/input some of you may have.
My initial thought was a gasket, head maybe.
Now I think water pump/impeller maybe.
No internal clunking so I rule out conecting rods or anything major like this.
During the fiasco, the temp was relatively normal 225 or 240 if I recall, but it was not off the chart.
Any thoughts will be greatly appreciated.
Glad to be part of the group!!!
Doug

Re: Mercruiser smoking/overheating
 

225-240 is way hot. Hopefully you aren't recalling those numbers correctly.
Sounds like something is cracked to me. Let us know what you find out.

Re: Mercruiser smoking/overheating
 

Doug,
That sounds very similar to our experience with our 95 Davanti a couple of weeks ago. In our case it turned out to be a bad impeller and water pump failing to cool the engine down. When it happened to us, the engine got to around 240-odd and the pressure in our closed cooling system that the coolant sprayed on the engine causing a bunch of white smoke.
Sanu

Re: Mercruiser smoking/overheating
 

Mechanic has looked...bad water pump.
I appreciate the comments.
Here's to happy/sage boating!

Re: Mercruiser smoking/overheating
 

I would also check your intake to make sure they are not clogged. Not sure if yours is on your outdrive or under the hull like mine. Since it is the first time you ran the boat this season, the holes may be clogged with something.

BTW, I grew up in the Howard Lake/Winsted area in Minnesota...too dang cold up there for me now!

Re: Mercruiser smoking/overheating
 

What was causing all the steam?

Re: Mercruiser smoking/overheating
 

Replace the thermostat as well. Once the impeller goes bad small parts of the impeller travel up the water supply hose and can block the thermostat either open or closed. To check for debris in the thermostat you need to remove the thermostat. Why not replace the thermostat while you have it in your hand?