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Old 19-06-2019, 12:23 PM   #1
CRD
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Country: England
Location: Somerset and Exmouth
Occupation: Retired Aircraft Engineer
Interests: Classic Cars. Shooting. Rebuilding anything
Boat name: Freespirit
Boat make: Tremlett 21 Fisherman
Engines: Mercruiser 3.0 LX
Cruising area: Exmouth

Join Date: Apr 2019
Location: Somerset and Exmouth
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Tremlett 21 with Overheating Mercruiser 3.0 LX

Hi All,

I have purchased a Tremlett 21 with a Mercruiser 3.0 LX inboard.
It has not been in the water yet but I wanted to get it running on dry land before the launch.
Purchased a 200 ltr plastic tank to run it. Fired up without difficulty but started to overheat, so shut down. Put a hose and ear muffs on and no problem at all, running at 165 ish

Is this an indication of a restriction in the system somewhere and can anyone point me in the right direction to solve the issue.
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Old 20-06-2019, 03:33 PM   #2
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Country: In the UK, in an offfice, looking out the window at the rain.
Occupation: Chartered Engineer
Interests: boats, water, snow, football
Boat name: DoubleSix
Boat make: Ring 21c
Engines: Opti 200
Cruising area: Lyme Bay

Join Date: Aug 2012
Posts: 124
Quote:
Originally Posted by CRD View Post
Hi All,

I have purchased a Tremlett 21 with a Mercruiser 3.0 LX inboard.
It has not been in the water yet but I wanted to get it running on dry land before the launch.
Purchased a 200 ltr plastic tank to run it. Fired up without difficulty but started to overheat, so shut down. Put a hose and ear muffs on and no problem at all, running at 165 ish

Is this an indication of a restriction in the system somewhere and can anyone point me in the right direction to solve the issue.
It depends how long the engine was running before it started to overheat. If you are running on flush muffs with a good pressure and flow then I would expect it to run without overheating ( if you are just on idle). If running in a tank then you are slowly heating that water up and then recirculating it,so the engine will be taking in warm (or hot) water. Turbulence in the tank will also mean it is somewhat aerated. i won't try to sound clever with lots of technical terms but aeration and introdcution of hot water means that tank cooling will not perform as well as the flush muffs. A Flush muff is a total loss system so its always getting cold water in.
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Old 20-06-2019, 04:38 PM   #3
CRD
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Country: England
Location: Somerset and Exmouth
Occupation: Retired Aircraft Engineer
Interests: Classic Cars. Shooting. Rebuilding anything
Boat name: Freespirit
Boat make: Tremlett 21 Fisherman
Engines: Mercruiser 3.0 LX
Cruising area: Exmouth

Join Date: Apr 2019
Location: Somerset and Exmouth
Posts: 4
The engine was getting hot instantly running in the tank but stayed cool on the muffs. I have taken off the riser and exhaust manifold, the riser has some rust in the waterways but the manifold seems clear. I intend to make the engine a sealed system so the raw water pump will just cool the exhaust.
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Old 21-06-2019, 07:12 AM   #4
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Country: In the UK, in an offfice, looking out the window at the rain.
Occupation: Chartered Engineer
Interests: boats, water, snow, football
Boat name: DoubleSix
Boat make: Ring 21c
Engines: Opti 200
Cruising area: Lyme Bay

Join Date: Aug 2012
Posts: 124
Quote:
Originally Posted by CRD View Post
The engine was getting hot instantly running in the tank but stayed cool on the muffs. I have taken off the riser and exhaust manifold, the riser has some rust in the waterways but the manifold seems clear. I intend to make the engine a sealed system so the raw water pump will just cool the exhaust.
Out of interest, what are you going to do to make it a sealed system?
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Old 23-06-2019, 05:01 PM   #5
CRD
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Country: England
Location: Somerset and Exmouth
Occupation: Retired Aircraft Engineer
Interests: Classic Cars. Shooting. Rebuilding anything
Boat name: Freespirit
Boat make: Tremlett 21 Fisherman
Engines: Mercruiser 3.0 LX
Cruising area: Exmouth

Join Date: Apr 2019
Location: Somerset and Exmouth
Posts: 4
Quote:
Originally Posted by DoubleSix View Post
Out of interest, what are you going to do to make it a sealed system?
The main Item will have to be a large heat exchanger made of copper. I was contemplating a swimming pool exchanger but not sure about the heat transfer. A header tank from a VW Diesel engine, because I've got one, and hoses and pipe work made to suit.

From what I have gleaned from the net, overheating is a very common fault so if I turn it into a sealed engine, over half the problems should disappear.
I am very new too boating but know sea water and metal don't go together.

I have looked at the kits from the various American companies and there seems to be about 500 dollars charged for bolts clips and various fasteners.
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Old 24-06-2019, 03:34 PM   #6
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Boat make: Colvic 35 Suncruiser / Phantom 16 / Zodiac 420 YL / RIB / Apollo 9
Engines: 2 x Perkins Sabre 225ti / Mercury Pro XS 115/ Tohatsu 2.5 / Mercury 25 / Mercury 50
Cruising area: Thames Estuary / River Crouch / Salcombe

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You could try using this RYDLYME Marine: The Ultimate Biodegradable Marine Descaler! | RydLyme Marine

I have used it successfully on outboards. I brought I cheap pump off ebay and some hose leg in a container and left it running through the system for a couple of hours did the trick for me. you will need at least 5L I guess so about 60 for the rydlyme, 10 for a pump off ebay. And a plastic storage box from a bargain store. Plus a bit of hose.
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