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Old 11 July 2016, 17:39   #1
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Irregular tell tail on a brand new Mercury 25hp

Hi guys,

I just got a brand new Mercury 25 HP that was never used but sat in the garage since 2004.

I took it for a first run on my SIB, but noticed that the water flow was very irregular from the tell tile. It was taking time to start peeing, then for few secs there was a very steady flow, the in turned white, like full of bubbles, then stopped completely.

This thing was repeating at regular intervals, no matter if I was running WOT or just idling. I tried different speeds, but the same result: water was running for about 30 sec, then stopped for 30 sec, then started again.

I know this engine never had the implelor changed, but it was never used either.n

Could anyone give me advice about the issue? Thanks for help
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Old 11 July 2016, 17:56   #2
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Change the impellor asap, if only due to its age & to eliminate it as a potential problem. It's 12 years old & the vanes can take a set plus they will deteriorate with age & cracks are likely to appear esp at the vane roots.
Delay in telltale from cold likely to be thermostat warming up not passing quantity until it opens. Increase & decrease in volume also possibly the thermostat opening & closing.
Do you have a temp gauge fitted?
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Old 11 July 2016, 18:00   #3
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Agree re swapping impellor just due to age even if it looks perfect. The tell tale does come and go on these due to the thermostat but usually at lower speed/idle... when up to speed the flow is usually constant.

A quick check would be to pull the stat out and test run without it. Also I always check the basic operation of an old stat in a saucepan.
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Old 12 July 2016, 01:04   #4
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Quote:
Originally Posted by Fenlander View Post
Agree re swapping impellor just due to age even if it looks perfect. The tell tale does come and go on these due to the thermostat but usually at lower speed/idle... when up to speed the flow is usually constant.

A quick check would be to pull the stat out and test run without it. Also I always check the basic operation of an old stat in a saucepan.
Hi all

That's the thermostat kicking in and out

Edit: early morning just relised the post before says it.

Edit:already mentioned sorry.
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Old 12 July 2016, 02:25   #5
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Thanks for your replies, guys, appreciate your input.

I will replace the impellor immediately.

I'm just surprised about the thermostat, if it is brand new how could a problem occur? Should I replace it as well?

Cheers
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Old 12 July 2016, 02:32   #6
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Its designed to do that on that model of engine. The thermostat is holding the water in the head then dumping the water when up to temperature. The tell tale will be scalding hot water.
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Old 12 July 2016, 02:40   #7
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I am not familiar with Mercury motors but most other engines the telltale is ported off separately from the thermostat so should always be constant.
This is the function of the telltale,so you always have an eyeball on the pump.
The water from the back of the leg is variable due to the thermostat.
Quite often if an engine has been sitting for long periods you can get little bits of salt/corrosion that bung up the telltale , you can try a bit of soft wire or blow back up with air, this though can dislodge it and it may come back again.it is much easier to sort in a tank rather than on the boat .
And totally agree....replace the impellor...they can set a little then crack when old.
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Old 12 July 2016, 02:41   #8
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Does it means it is normal? Indeed, the water flow is warm at the beguining, when it starts to flow, thick and nice. Then is starts getting thinner, and hotter, then it stops completely. And re-starts flowing in some 30 sec. Is this a normal tell tile for this model? Do I have to leave everything as it and just replace the implelor?

Thanks for help
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Old 12 July 2016, 02:44   #9
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Just read the reply above........
Mercury always were a little odd,different systems, special spanners etc etc
I never worked on them and farmed the work out to my nearby Merc dealer.
The won most of the racing though.
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Old 12 July 2016, 03:01   #10
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there is a procedure for engines that have not been used, only stored for a number of years. I cant remember what it is now , mostly w/pump impeller change fuel filters change, you need to contact your local mer/mar dealer. Has it been registered if not get it registered, obviously there is no factory warranty, but if any mods come out at a later date, the factory will have your details.
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