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Old 12-13-2008, 03:15 AM   #1
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Hi, I threw off the mooring lines last week the first time in a long time. I've been working on Dream Maker for awhile now but last weekend I decided to take the wife for a sail. This was the first sail together by ourselves so I was hoping all would go well.

Well I'll cut to the chase, motored over to get fuel, tied up, filled up (all Good). Fired up the Yanmar and started to reverse out and lost suction to the raw water pump. Now I've had this problem before while under sail so I have since put in a new impeller (old one looked ok kept as spare)

So my question here is any ideas on why I would be loosing suction under sail (with sea cock open) and motoring in reverse (I have not had any problem running the engine at the mooring since I change the impeller some 4 months ago)

Second problem. We had a nice nights sleep (all good) until the anchor had to come up. Engine going pushed the button up came the chain, well about 30 mtrs (100 ft) then crunch,grating stopped. (Now I know why I need a windlass)

Question here is has anyone got a manual and parts listing for a MUIR CHEETAH 2500 horizontal windlass in PDF or WORD.

All Good

Kevin
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Old 12-13-2008, 07:03 AM   #2
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One guess about losing suction on your raw water -- that the inlet for it has a "scoop" which faces forwards, and you create cavitation over the scoop when motoring in reverse (cavitation probably caused by water being forced in reverse over the scoop by the action of the prop).

Unfortunately the only way to fix that is a haulout and replace the scoop with a standard strainer type arrangement.

Del
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Old 12-13-2008, 08:58 AM   #3
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Hello Kevin,

It could be a simple problem of an air lock in the system. Guess that if you had a scoop in the intake through-hull , the problem would have always been there. Sometimes impellers that don't get much use can be damaged be encrusted salt - even barnacles.

If you send me a PM (personal message) with your email address I will send you a Muir Manual that I have on file for the Cheetah 2500 in pdf format.

Richard
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Old 12-14-2008, 04:18 AM   #4
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Thanks guys. It beats me, as for the scoop it doesn't have one, there's just a hole in the bottom (maybe it needs a scoop) but Dream Makers 20 years old and I suspect it's never been changed. I've gotta work out something because the first time it did it we melted the plastic muffler.

I just thought of something, my son changed alot of hosing on the engine. There wouldn't be any sort of one way valve on this sort of system after the pump and before the muffler to restrict back flow.?

Kevin
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Old 12-14-2008, 10:06 AM   #5
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Hi Kevin,

PDF Muir manual on its way by email - hope it throws some light on the problem.

Richard
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Old 12-15-2008, 09:16 AM   #6
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Thanks Richard. I've had a look and I'm wondering if the motor and gearbox come as separate parts, which in the parts listing only shows one part number. I think I'll get onto Muir and ask and then I supose also ask the heart attack question of the costs.

Soon to be out there,

Kevin
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Old 12-23-2008, 10:03 PM   #7
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If everything - water intake is normal at idle or low rpms and then at high rpm's the engine cavitates or looses water then you might have clogged intake hoses. You mentioned 20 years old. Intake hoses accumlate barnacles and other type of sea creatures and floura which will restrict the water flow enough to cause the cavitation and lose of raw water.

Once every two years I have to shut my seacocks and suck out the water in the strainer with a vacuum and then pour muriatic acid in to dissolve the accumlated barnacles and other organics. However do not do this technique if you have bronze fittings/thruhulls as the acid will eat away at the metal. Instead you have to remove and replace the hoses with new.

One in-water test for the brave of heart is to shut the seacock and then remove the top to the raw water strainer. Then open the seacock - there should be a dramatic surge of water coming up out of the strainer. If the water flow is less than dramatic or minimal, then you definitely have clogged hoses.

I had one raw water system (I have separate port and starboard intakes) would only dribble water when the strainer cover was removed. An expensive diver could not find anything blocking the thruhull and from the strainer down it looked fine. I hooked up a positive vane pump to the system and turned it on - instantly a loud sound and burble and then an exactly 1.5 inch diameter little fish was sucked out of the hose into the strainer.
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Old 12-24-2008, 05:53 AM   #8
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Hi guys. I've had a look at my strainer as osirissailing mentioned. The water doesn't come into the boat as the strainer is about 12 inches or more above the water line.

Is this correct or should the strainer be on the water line?

It seems to me that if it was lower the pump would always have a head of water to draw on and if the intake hosing from the thru hull is clear I should never have this problem.

On the Muir. I contacted them and I can buy any part of the motor or gearbox I need but they haven't gave me any pricing as yet. So I hope to repair it and still have some change in my pocket.

Happy Hols

Kevin
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Old 01-14-2010, 01:26 AM   #9
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The sea strainer can be above the water line, BUT there are issues, just as you noted with bad things happening going astern. The real key is entrained air in any high spot in the system, the worst being the rubber impeller pump.

We had, new from builder, a fridge cooling pump that worked fine, until running hard and surfing the boat, the air bubbles would accumulate at the high spot, the jabsco pump, the pump would air lock and the high pressure shutdown would stop the compressor.

I fixed my issue by making a alu mount that re-oriented the pump 90 degrees, so that the discharge was higher than the intake, and lead the discharge hose away with a rise so that the air bubbles harmlessly went through the pump and have surfed the boat in big waves over 18 knots without any problems....

In your case, the plastic exhaust parts melted. Take a careful look at all the hose runs, especially if you have changed things recently, with an eye to insuring there are no 'loops' to accumulate air and airlock the system, and many jabsco type pumps have symetrical mounts (2 bolts or 4 bolts) that would allow you to adjust the pump orientation to align the discharge upward (best) or at least horizontally to shed air, and your problem astern should be solved.

Another thing you might want to consider is a no flow alarm for the engine, we have them on both the main and genset, so we get visual and audible warning if water flow is impeded (plastic bag, jellyfish, kelp knob....ask me why I know this.....)

a very solvable problem, even if you need to temporarily put clear hose on the system so that you can see what is going on

very best of luck...

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Originally Posted by seaescape View Post
Hi guys. I've had a look at my strainer as osirissailing mentioned. The water doesn't come into the boat as the strainer is about 12 inches or more above the water line.

Is this correct or should the strainer be on the water line?

It seems to me that if it was lower the pump would always have a head of water to draw on and if the intake hosing from the thru hull is clear I should never have this problem.

On the Muir. I contacted them and I can buy any part of the motor or gearbox I need but they haven't gave me any pricing as yet. So I hope to repair it and still have some change in my pocket.

Happy Hols

Kevin
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