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Go Back   SailNet Community > On Board > Gear & Maintenance > New engine intake thru-hull mounted wrong?!?
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Thread: New engine intake thru-hull mounted wrong?!? Reply to Thread
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Topic Review (Newest First)
05-21-2009 05:45 PM
FishFinder Yeah glad I was paying attention, the thru-hull they used yesterday looks to be similar to an old cheapy one I have for above-water bilge pump discharge ... which is brittle and has cracked.

BUT everything is fixed now, all marelon down there and scoop facing aft. 3rd time's the charm. She's in the water now, no leaks, job finally done right. Next time I'll DIY for sure.

Thanks everybody this forum is awesome.
05-21-2009 03:46 PM
Maine Sail
Quote:
Originally Posted by FishFinder View Post
Saga continues, turns out the replacement thru-hull they put in yesterday was NOT marelon, it's some kind of other plastic .... they're telling me this other plastic is fine, thought this was a no-no below waterline. Doesn't matter we're taking the whole thing out again today.

Sounds like it's time to find a new boat yard these guys are clowns!!

The other alternative is to learn to DIY, save some BIG money and generally do a better job..
05-21-2009 02:22 PM
JomsViking FishFinder,
It has to be marelon, there's no plastic substitute for that AFAIK. You should probably add this yard to the list that someone (SD?) created about experiences with marine companies.
05-21-2009 02:14 PM
FishFinder Saga continues, turns out the replacement thru-hull they put in yesterday was NOT marelon, it's some kind of other plastic .... they're telling me this other plastic is fine, thought this was a no-no below waterline. Doesn't matter we're taking the whole thing out again today.
05-20-2009 09:29 PM
FishFinder Pic of install (it's since been painted). The thru-hull under the scoop is the part I'm hoping is marelon ...
05-20-2009 09:20 PM
FishFinder Today the yard removed the entire thru-hull and reinstalled, reversing the scoop so it now faces aft. I think all is good ... they had to put in a new thru-hull under the scoop because old was destroyed on removal. It looks a little bit different from the other marelon ones ... hard to tell it's covered by the scoop now. They wouldn't put in a non-marelon plastic thru-hull under the waterline would they? I'm paranoid now. I'll need to verify that I suppose before launch tomorrow.
05-20-2009 07:53 AM
r.furborough The only thru-hulls that should have a forward facing scoop on a sail boat is the intakes for the for HVAC or refrigeration, they assist in the pumps keeping their prime.

The yard that fitted your thru-hull for the engine raw water intake is incompetent, it is a rookie mistake and even if a rookie installed it there should have been a final inspection before launching by an experienced person. The Yard should haul and correct the problem without you incurring any costs!

Mainesail is correct, raw water pumps do not block the flow, there are wear items in a pump, the 'cam' and the 'cover plate', even a new impeller will not seal properly if these are worn, add a worn impeller to the mix......

It does not take much wave action or to force water into a forward facing thru-hull, particularly when the boat is heeling and the thru-hull is closer to the water-line and the relative height of the thru-hull and the engine is reduced due to the hulls lateral rotation as it heels.

If you cannot get satisfaction with the yard, until you get this corrected, I would not sail the boat without the thru-hull being closed to prevent the possibility engine damage..
05-20-2009 12:21 AM
FishFinder negrini you got a pm
05-20-2009 12:04 AM
negrini Good extract from the book (I have it too !!). I have an extract from VOLVO parts book (part 26.1-3, cooling water intake chapter 26). This explicity states the strainer must be faced FWD for powerboats only, while must be faced AFT for sailboats. When I installed my MD2040 with SailDrive, a very nice US VOLVO dealer (I can't remember who, but it was in New York) handed me a copy of installation manual for engines, and that was years ago. Again, I'm very surprised your boatyard is not aware of this well known old specification .... send me your e-mail so I can send you the pdf, then you can print and show to them.
05-19-2009 11:23 PM
FishFinder Well I found the proof I was looking for ... from Nigel Calder's book "Marine Diesel Engines":

"A less common cause of engine flooding is the installation of a scoop-type water inlet facing forward on the outside of a sailboat hull. Anytime the boat is moving at more than a few knots, this generates pressure in the raw-water system. In normal circumstances, the vanes in the rubber impeller raw-water pump will hold this pressure at bay when the engine is not running. But if the vanes get damaged, water will be driven up through the heat exchanger and into the exhaust, where it will build up and flood the engine. Scoops, if used, should be fitted backward."

So that sucks. Going to have to talk to the yard. Based on what everybody said here, it sounds like the install will most likely work OK which is good to know. But like MaineSail and my book says, there is a chance it will not and at $82/hr they should have known better.
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