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Old 29-06-2016, 08:35   #16
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Posts: 59
Re: Engine raw water leak

I just helped a friend troubleshoot his raw water system on his 1989 Hunter 35.5 Legend with a 3GM30F from the raw water intake all the way to the exhaust. We took apart everything and questioned everything. He was not getting enough water flow. We closed the seacock and cleaned the strainer and ensured that the seal was good on top. ensured the hose was clear to the impeller. Dismounted and rebuilt the impeller housing with a new impeller, cleaned the mating surface of the housing to the cover and replaced the seal. I would recommend replacing the hose with the t-fitting and repipe to the heat exchanger. we reverse flushed the heat exchanger with fresh water we replaced the hoses going to and from the siphon break to the mixing elbow and replaced the manifold and mixing elbow. Evidently his problem was a impeller sucking air from the cork seal, the hose from the siphon break to the mixing elbow had junk in it and the mixing elbow had junk in it.

Don't be afraid to take this system apart.

Just make sure your seawater intake seacock is closed prior to doing anything so you don't flood your boat.

If you have any questions, please PM me and we can talk on the phone.

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Old 29-06-2016, 10:30   #17
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Location: East Coast Florida
Boat: Chris Craft 38 Commander 1965
Posts: 158
Re: Engine raw water leak

Raw water pump impellers and seals are just one of those things that go on your preventive maint list. Do not wait till you see a leak or have an engine overheat. If the seal goes first then the pump leaks and you may not know it for a while and then the water intrudes into the bearing and then they have to be replaced as well and or it scores the shaft and then you might as well get a whole new pump as the cost of the bearing, seals, impeller and shaft is greater than a new pump.
I change my impeller every two years - fail or no fail. If no seal leak noticed I may skip the seals part one time but do it the next time for sure. If an impeller fails by shedding a blade and no leak then just the impeller if within the two yr period.
Put on the list with filters, oil change, battery water, etc.

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Old 11-07-2016, 07:58   #18
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Location: Lexington, KY
Boat: Hunter 27
Posts: 2
Re: Engine raw water leak

Originally Posted by sailorchic34 View Post
I'm with A64pilot. It's probably the water seal in the raw water pump leaking. Only leaks with the engine running, at least at first.

There is a slot under the raw water pump that lets the water that leaks past the seal to drip out and not destroy the bearings. What happens is the drip falls on the hose and runs to the low point and then drips. Really hard to see when the engine is running.

Easy to replace with a pair of snap ring pliers.

Remove raw water pump.
Remove back impeller.
Remove pulley then remove snap ring.
Then pull the bearing shaft assembly out. Might have to Gently tap it out from behind. Use a Brass drift

You will find that there is a mineral buildup around the water seal and shaft. The water seal then can be tapped out.

The shaft might be scored but that's not a big deal for the first go round. So sand the shaft clean where the water seal. Sometimes that's all you need to do. But since it's apart go and replace the seal and bearings too if there is slop in them.

Take the bearings and water seal to a local bearing supply house. They should be able to give you matching ones as they are very common size. Get two water seals to have one for spare.
I'm new to this forum and joined because of a similar issue with my 1GM10 on a 1993 Hunter 26. There had been no issues until I replaced the impeller, O-ring, and gasket this spring. I noted there was a leak so I tightened the screws but no change. So, I replaced these parts again and applied copious Lithium grease. Then I noted a leak from the hose at the intake to the impeller. I trimmed that back and tightened on a new hose clamp. All seemed leak at 1200 RPM but when I revved to 2500 RPM I noted a slight leak. It seems to b coming from two little vents from below the pump housing.
I read your post about a snap ring, bearings, and water seal...and shuttered. There is no dealer, supply house, or Yanmar service for 200 miles. All the work needed in my club has to be done by ourselves and I'm not mechanically gifted.
So to leaks were present until I performed what was supposed to be routine maintenance, as I've done previously.
I guess I should have left well enough alone.
Any suggestions?? I'd appreciate any ideas, including condolences (!).
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Old 11-07-2016, 09:31   #19
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Location: East Coast Florida
Boat: Chris Craft 38 Commander 1965
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Re: Engine raw water leak

Classic example of getting burned for doing the right thing - but not realizing that partially opening a can of worms let's them find a way out.
IMO any raw water pump should be preventively serviced on a regular basis - that interval needs to take into consideration the hours of operation and the time between servicing.
My rule of thumb is every 2 years remove and replace impeller, and gasket - leak or no leak. At next service interval or if a leak develops between intervals - do a complete breakdown and servicing to include: completely disassemble by removing shaft, seals, bearings, wearplates, etc. Anytime there is a leaking seal you can never know if water got to the bearings. If discovered early the bearings may be saved. When the bearing(s) are out slowly rolling them and feeling their smoothness to spinning and listening for any very slight gritty sound to evaluate if a new bearing is needed. This is a difficult one to quantify and only experience will tell a good bearing from one that will fail.
Reassemble with something like Triple Guard Grease. A very dense, stiff, waxy grease much more water resistant than lithium grease on the front and back of the bearing cases. This will give a little time to prevent water intrusion into the bearing race when leak starts.
My experience has been that once an impeller is removed/replaced more than once or twice the seal gets stressed and will soon fail so bite the bullet and do the whole job if has been a while or you do not know when the last complete service was done. Half a job ends up being One and a half jobs.
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Old 11-07-2016, 18:25   #20
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Location: Lexington, KY
Boat: Hunter 27
Posts: 2
Re: Engine raw water leak

Thank you so much. I appreciate the advice.
Just heard there may be a Yanmar mechanic who has worked on a friend's boat. He may be a Yanmar tractor mechanic but I'll go with what I have if I need to go into the shaft, bearings, etc.
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Old 11-07-2016, 23:34   #21
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Location: Anchorage, AK
Boat: Cheoy Lee 32 Offshore, 1979 (Ray Richards)
Posts: 39
Re: Engine raw water leak

SailorChic was right OnTheMoney. Her detailed response was VERY good.

We repaired it today and will try it out tomorrow.

I took it to Bruce my friend and Audi mechanic and we took it apart. He used some heat to get parts to come off the pulley shaft. I bought new bearings, oilseal, snaprings and o-rings from the local bearing store-- totaled about 40 or 50 $.

I helped Bruce put it back together. With some research I found Yanmar's diagram. Boy-- they sure don't make it easy to but non-Yanmar pumps--- the pumps are made by Johnson but it is hard to feel warm and cosy about buying a 'spare' Johnson pump.

Tomorrow I will install.

Thanks to all!---- Rick

PS--- do youall think it is 'wise' to have an entire spare pump on board????
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Old 12-07-2016, 16:47   #22
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Re: Engine raw water leak

A spare may save you one day when your where no pump can be had, and yours isn't repairable. Flip side is you'll never never need what you have in spares.
I have a spare of every pump on my boat, maybe anal, but it seems pumps are something that requires constant attention, or maybe I'm doing something wrong?

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