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airbesar

Only overheats at startup idle

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airbesar

Sorry if this has been covered - I searched and couldn't find a discussion on this particular issue.

2000 wakesetter.  While idling after startup, the engine overheats to 200 on the gauge.  If I then run the boat at 20 or faster, the temp returns to normal.  The odd thing is that the engine never overheats again on the outing, even if it's idling for 15 minutes.

Yesterday, I tried putting the boat in neutral upon startup and running it at a higher than idle rpm while at the dock.  The gauge temp was going up, hadn't reached 160, but the engine was clearly overheating.  Had that smell.  When I put the throttle at idle, the engine stopped, wouldn't restart.  Waited 10 minutes, restarted engine, had our outing with no overheating.

Looking for suggestions.  Thanks.

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teamerickson

@Fman Had similar issues on a 2015. Maybe he has some thoughts.

Impeller not priming?

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Chaabo

Try a new impeller!

Sounds like yours needs some initial higher rpms to prime the cooling system.

I had that with a globe blue impeller (brand new) that always needed me to revv the engine on first start-up. Went back to the std black neoprene/rubber one and all was good again.

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formulaben

For sure get a new impeller.  While you're down there remove the hose for the transmission oil cooler inlet and make sure it is clear too.

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Fman
10 hours ago, airbesar said:

Sorry if this has been covered - I searched and couldn't find a discussion on this particular issue.

2000 wakesetter.  While idling after startup, the engine overheats to 200 on the gauge.  If I then run the boat at 20 or faster, the temp returns to normal.  The odd thing is that the engine never overheats again on the outing, even if it's idling for 15 minutes.

Yesterday, I tried putting the boat in neutral upon startup and running it at a higher than idle rpm while at the dock.  The gauge temp was going up, hadn't reached 160, but the engine was clearly overheating.  Had that smell.  When I put the throttle at idle, the engine stopped, wouldn't restart.  Waited 10 minutes, restarted engine, had our outing with no overheating.

Looking for suggestions.  Thanks.

I had similar symptoms on my 409.  What engine is in your boat? Guessing you have a 350 which is not a reverse cooling engine like the 409.  If it's a 409 I have something you could try.

If it is a 350 the only other suggestion I would try is replacing the thermostat, could be sticking and old.  They are cheap and easy to install.

 

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airbesar

Thanks for the ideas.

For Fman: it's a 350.  A new thermostat sounds like a good idea, along with an impeller.

Seems like the starting point for most overheating problems is the impeller.  It's just odd to me that there isn't a problem after going faster, even if idling later.  The impeller isn't brand new so that could be a problem but since nothing was changed on the boat from last year to this, it's not a case of a weird new impeller causing a problem.

In 18 years with this boat, I've never had this problem so something is going on to create it now.  The possibility of needing to prime maybe is because the impeller is damaged, or perhaps sticking when idling at startup.  Interesting though, that when I reved up at the dock, the overheating occurred anyway.  So maybe the extra water pressure when moving forward at speed, kicks a sticking impeller into action.  Or it's back to the thermostat possibility.

Anyway, I think starting with the thermostat and impeller is the way to go.

Thanks for the ideas and would welcome any other thoughts.

 

 

 

 

Edited by airbesar
typos

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BlindSquirrel

Yeah, I agree with checking the impeller first. The reason it doesn’t overheat when you’re moving is the water is being rammed in there by the scoop on the bottom of the boat instead of just the impeller sucking it up. It is then primed so you can idle and not overheat.... well until you turn off the engine again. The beer can looking device attached to your cooling hose is the transmission cooler with a screen on it you need to make sure is clear too.

I’m betting your impeller is damaged. How old is it?

Edited by BlindSquirrel

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CanVLX

It could also be a small amount of air getting into your cooling system. Check that all your hoses are tight and gaskets/seals are not leaking. 

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soundingbusy
On 21 August 2018 at 11:03 AM, Fman said:

I had similar symptoms on my 409.  What engine is in your boat? Guessing you have a 350 which is not a reverse cooling engine like the 409.  If it's a 409 I have something you could try.

If it is a 350 the only other suggestion I would try is replacing the thermostat, could be sticking and old.  They are cheap and easy to install.

 

Fman, I am interested in your comment " If it's a 409 I know something you could try"?.  Can you detail this?  Thanks

 

 

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Fman
4 minutes ago, soundingbusy said:

Fman, I am interested in your comment " If it's a 409 I know something you could try"?.  Can you detail this?  Thanks

 

 

The symptom with my 409 was when I would launch the boat and only idle or drive under 1500 rpms it would slowly creep up to 200 degrees and set off the temp alarm.  Once I would throttle up to 3000 rpms for approx 5 seconds it would run all day at 165.  This symptom would repeat itself every time I launched the boat.

I ended up trying all kinds of fixes,  new heater circ pump, thermostat, impeller, etc.... finally the only thing that helped was removing the small check valve and drilling a few extra small holes in the thermostat.  This would allow water to circulate before it opened up.  It would keep the temp down to 185 until I ran over 3000 and then it would stay at 165.

This is the response I got from Indmar...

The 6.0L engine has a different style cooling system referred to as a reverse flow system. In the standard 5.7L engine cooling water enters the engine through the water circulating pump and is pushed through the engine. The water exits the engine through the thermostat housing and thermostat. The 6.0L engine works just the opposite. Water enters the engine through the thermostat housing and gets pulled through the engine by the water circulating pump. The water leaves the engine through the circulating pump.

When the boat is pulled out of the water, much of the water drains out of the block, leaving the water circulating pump dry and when the circulating pump is dry, it does not pump. When you start an engine that has been drained, the system relies on the raw water pump (rubber impeller pump) to force water into the block so the block fills with water and the water circulating pump can function. One of the problems is that when the engine is cold, the thermostat is closed so only a small amount of water can enter the engine through a bypass hole in the thermostat till the thermostat gets warm and opens. The other issue is that at low RPM the raw water pump does not push a large amount of water through the small bypass hole in the thermostat so it can take some time to fill the system. We typically recommend that with a drained  6.0L engine that after you start it, increase the RPM to 1500 or so to fill the engine and get the circulating pump working. Removing that floating check-valve from the thermostat will allow the block to fill faster.

Start the engine and let it run for a minute or so then bring the RPM up to 1500 or so through the warm-up process and you should be just fine.

 

 

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hunter77ah

^ exactly. I do this every time now and it works. 

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