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Old 24 September 2014, 04:52   #11
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Country: UK - England
Town: Sticks, N.Yorks
Boat name: Tamanco
Make: Honwave 3.5AE
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If it's got one it's there for a reason. Make sure it's working and fit it.
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Old 24 September 2014, 05:33   #12
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Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
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Engine: Merc 60 Clamshell
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main reason is to warm it up quicker.

My old clamshell type ran from it;s inception to something like the last but one year of production with thermostat & poppet valve. The last year or so (I'm sire someone like Uncle Al can confirm exact dates!) the two were dropped, to the point the castings they sat in changed.

I was rebuilding & went for the "latest level" on the rebuld - Differences are now it dribbles at idle (used to squirt) and I had to up the idle mix by about 1/8 of a turn to offset the overkill cooling with the poppet valve essentially permanently open.

But I am mostly crusing, so low speed cooling efficiency is a lower priority for me.
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Old 24 September 2014, 05:34   #13
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Country: UK - England
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Boat name: Nimrod II
Make: Aerotec 380
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My opinion... if they are fitted with a stat keep it.

There can only be so many reasons why you have no water at the tell tale.....

As others have said double check the impeller is actually being driven and not spinning on its bush or failing to be driven by the shaft.

I wonder what you are probing the tell tale with... I find a bit of Bowden cable inner ideal as its strong and flexy.

The intake isn't blocked in any way?

Is the powerhead to pump pipe in the leg joining OK after the lower unit was replaced?

I guess my next move would be to remove the gearcase again then flush down from the pump out through the inlet strainer... then remove the thermostat and flush through from the pipe in the leg to the powerhead and also from the stat housing back down the leg pipe.
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Old 24 September 2014, 09:12   #14
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johnyp it will be buggered because you have cooked the wax in the thermostat bulb, the proper way to test them is, look to see what temprature is stamped on thermostat, with a thermometer and thermostat in container of water slowly bring up to temprature and watch it open /not open. I used to get some hot water from the coffee machine check the temprature and imerse the thermometer into the water.
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Old 24 September 2014, 11:45   #15
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my mercury 15 2006 year pumps water strongly and constantly when cruising or flat out but if I slow to 5mph it stops and flows intermittently I have been told its as it should be
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Old 24 September 2014, 12:10   #16
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I'm servicing my Mercury 15 today so have the workshop manual open.

Interestingly it gives the water pressure spec with and without thermostat. At 5000rpm the pressure is the same with/w.out at 5-7psi however at 750rpm idle the spec is 0.5 to 1.5psi with a stat and 0 to 1.0psi without. Seems if you take the stat out you are losing pressure to the tell tale??
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Old 25 September 2014, 04:12   #17
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Country: UK - England
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Hi all thanks for your comments/advice i have checked all of these and will give it a try this weekend let you all know how it goes.
thanks again
johnyp
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