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motor overheating

3125 Views 32 Replies 9 Participants Last post by  newbie
new boat has an 89' merc 470, with a FWC system. while running today, engine overheated since i wasent paying attention to my guages
boat overheated pretty **** bad, smoking to holy **** and spewing anti0freeze to the bilge. if you were in jones this morning, i was the idiot with the smoke pouring from my engine, and doing the tow-of-shame back home.

ive ran the boat 4x prior to this, and quite hard in thursdays weather with no issue. only difference is today, since i left on dead low tide, i only have about 3.3ft in my canal, and i got a bit too close to the edge and was kicking up some nasty black muck. (had no choice, was a bulk-head barge parked in canal)

im assuming i have some sort of restriction of water flow somewhere now? but where do i start looking, and could me kicking up muck have caused it?? i would think so since i had no issues prior to this running the engine in water, or out with ears.
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My friend did the same thing with his Wellcraft, same motor. He likes to dredge the bottom too. He ended up packing his riser with crushed shells and sand, some small pebbles too. The heat exchanger was piping hot, hoses and all which told us at least it was working properly, but it wasn't exchanging the heat with the saltwater coming in. We pulled the outgoing hose off the riser at the back where it meets up near the rubber boot as the exhaust comes out. It connects the exchanger with the back of the riser. Stuck a garden hose in there, real quick started the engine and turned on the water. The pressure built up immediately because there was crap packed in there. He pulled the riser off and you could see the stuff inside the exhaust part where the water meets to exit the engine. He worked at it with a small hanger a lot of water and I think a real thin knife. He cleaned it out, put it back together with new gaskets and such. It works fine now. He had cleaned out a beach's worth of sand and stuff from his heat exchanger but did not realize that what was sucked in would also try to be forced out. It jammed up at the exhaust end of the riser. You'll see what I mean when you get the riser off. You'll see the inside collar that exhaust comes out and around that is the passage that water exits from. That small space was jammed with grit.
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If you didn't live half way to NYC I'd help you do it. Sometimes there is equity in peace of mind though and having an experienced mechanic do it may be best.
I'm tellin' ya dude, get yourself the repair manual and read it. The pictures and descriptions help you figure it out a lot. That riser will have like four long bolts to take out and the whole thing comes off. Real simple. Seloc, West Marine, buy one (the manual that is, not the store.) This is the kind of repair that you really can't screw up when you take the part off. Just remember what you did to get it off, have that other person with you write down the steps you take and draw simple stupid diagrams. Use a notebook, take pictures with your cell phone or better yet a digital camera. This repair is easy to do and will give you confidence in your skills to fix minor to moderate things. You'll save $100 an hour every time.
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