2008 Searay 340 Port Engine Overheating

Chris Crownover

Chris Crownover

Member
Apr 22, 2019
77
Seattle, Washington (Lake Union)
Boat Info
Searay 340 Sundancer
Engines
Mercruiser Sterndrives 740 hp
Kohler 5ECD
On Labor Day (coming back from San Juan Islands) I got an engine temp alarm on my Port Engine but both temperature readings on my smartcraft were around 180 which is nominal at 3400 RPM. I slowed down and the alarm went away, I then drove at 3400 RPM for about 3 hours before the temperature started ramping up and alarmed at about 200 and maxed out at 230 (some smoke coming from the engine).

I let it cool down to 170 and tried to restart and got a low voltage alarm.

What should I check first as to the cause for this?
 
Sounds like your impeller went bad OR I also had this happen when my exhaust riser let go...although my bilge pump was working as indicated on the dash.
BTW...You are lucky you didn't fry the engine at that temp...mine got almost that hot but I shut it down, smell was strong of rubber.
 
Don't forget to check your serpentine belts....Once one slips or disintegrates while under way your water pump/impeller stops pumping, and your engine overheats..... Not to mention your alternator stops charging your battery. (Low voltage)
 
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brewster16 said:
Don't forget to check your serpentine belts....Once one slips or disintegrates while under way your water pump/impeller stops pumping, and your engine overheats..... Not to mention your alternator stops charging your battery.
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I had that happen to me once just after getting up on plane. Starboard engine dropped into guardian mode while port was still at 4200 RPM. Boat shifted to starboard almost taking me out of the channel, alarms went off and smartcraft errors were scrolling. Once your brain processes whats going on you calm down but for a few seconds your certainly on high alert.

-Kevin
 
Chris Crownover said:
On Labor Day (coming back from San Juan Islands) I got an engine temp alarm on my Port Engine but both temperature readings on my smartcraft were around 180 which is nominal at 3400 RPM. I slowed down and the alarm went away, I then drove at 3400 RPM for about 3 hours before the temperature started ramping up and alarmed at about 200 and maxed out at 230 (some smoke coming from the engine).

I let it cool down to 170 and tried to restart and got a low voltage alarm.

What should I check first as to the cause for this?
Click to expand...


For what it’s worth my 8.1’s at 3200-3500 rpm have never reached 180 according to the smartcraft gauge. Both sides read 160-163 consistently. I’d start with the impeller and work from that point.
 
brewster16 said:
Don't forget to check your serpentine belts....Once one slips or disintegrates while under way your water pump/impeller stops pumping, and your engine overheats..... Not to mention your alternator stops charging your battery. (Low voltage)
Click to expand...
 

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Well based on the dust, looks like something is locked up/bad bearings. Which eventually broke the belt.
 
That looks terrible, you got some work to do there. Besides having a locked up acc. you need to get the rust off those pulleys. They can rust to a point where the ridges the belt rides on get pointed and sharp. Those need to be replaced, if they're not that bad get the rust off and paint them.
 
I'd say that the black dust you see is the crumbled and disintegrated serpentine belt. The belt has a lifespan and once it is exceeded it will crumble or partially tear (or completely break). If you don't know the age of your serpentine belt go ahead and replace it, otherwise it'll ruin your day.
 
brewster16 said:
I'd say that the black dust you see is the crumbled and disintegrated serpentine belt. The belt has a lifespan and once it is exceeded it will crumble or partially tear (or completely break). If you don't know the age of your serpentine belt go ahead and replace it, otherwise it'll ruin your day.
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Yeah I sanded and painted the pulleys and yes all the dust is the belt grinding as the motor kept going once the belt broke for a bit. Replacing the belt today and cleanup :) hopefully everything else is ok. It got up to 230 deg
 
techmitch said:
No crank/no start or cranks but won't start?
Were all of the pulleys free and quiet?
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It cranks but it makes a loud sound like something is locked up. Everything turns smoothly by hand…the water pump one is harder to turn but the same as the starboard which is working fine. I can’t turn the main shaft on either engine but I don’t think your supposed to be able to. Without the belt the main shaft tries to turn but again made the loud sound
 
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Pull the spark plugs and try again? Cylinder full of water from a possible blown head gasket from the overheat?
 
Is it trying to crank over and making this noise or is it fully cranking over and just failing to start? You said it tries to turn over then makes the loud sound. A cylinder full of water will not compress and you could be hearing the ring gear and starter gear grinding. If you pull the plugs and it cranks with a blast of water (coolant) out of a cylinder you have your answer.
 
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It s
Shenanigans77 said:
Is it trying to crank over and making this noise or is it fully cranking over and just failing to start? You said it tries to turn over then makes the loud sound. A cylinder full of water will not compress and you could be hearing the ring gear and starter gear grinding. If you pull the plugs and it cranks with a blast of water (coolant) out of a cylinder you have your answer.
Click to expand...
it started! Watching the temp gage now to see if it starts getting too hot
 
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