350 mag mpi overheat

QBhoy

Fleet Admiral
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Mar 10, 2016
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8,286
hi
so last week my friend (not mechanically minded) took one last run in his boat. After 20 mins he called me asking if a burning rubber smell is anything to worry about !
i asked him to check temperature. Was ok at that instant.
Masked him to open engine hatch and check the belt. At that moment it snapped. He then panicked and tried to drive in to shore slowly. Once he started to listen to me on other end of phone, I asked him to stop the engine ASAP. At that moment the alarm goes off briefly and temp gauge apparently just about 190/200 he said. He got towed back in.

Today I visit his boat for the first time. She is a bravo and has the belt driven pump. Should have said. The new belt has been fitted. I’m tasked with driving the boat from her mooring round to the slipway ramp to take her out for winter. After 10 mins of driving at no more than 1200 rpm, the temp climbs to about 180/185 maybe on gauge. I headed for the slip and tied up. With the engine back at tick over it looked like the gauge may be rising further but no alarm. I revved her a bit and she cooled down a bit. Shut it down an put on trailer.
If the pump is belt driven, the belt snapped, why would she be showing signs of the impeller being worn ? Surely it would just have stopped turning ?
Is it possible the other pump is damaged ? Not too familiar with this set up with the Bravo. I have the alpha and simple system.
Thanks
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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47,309
Pull the raw water pump, then check the impeller and the bearings. If the belt snapped, something is wrong
 

alldodge

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Mar 8, 2009
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Don't think its the pump, the pump just stops turning. Mine snapped many years ago cruising and alarm went off, so shut it down quick. Won't hurt to check the impeller, but if its damaged it was ready to go prior.

I would lean more toward something else happened
 

Lou C

Supreme Mariner
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Nov 10, 2002
Messages
11,803
I would check the pulley alignment with the other pulleys and also the bearings in the pump to make sure they are not seizing up causing the belt to break.
 

QBhoy

Fleet Admiral
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Mar 10, 2016
Messages
8,286
Thanks guys. Agree it seems strange to be the pump. Was working fine before. I’ll check the pulleys.
It’s raw water cooled and In fresh water.
 
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