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Old 18-01-2016, 07:35   #1
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Raw Water Exhaust (NOT)

First posted question, please bear with me:

Yammer 3GM sitting on hard 6 months, changed and lubed impeller, continuously filled raw water strainer with garden hose water, started the engine...fine.
Raw water initially spurted out the exhaust thru hull then stopped. Quit pulling water from the strainer too.
1) Diconnected hose from the heat exchanger, started engine, raw water pours out without obstruction with a good amount of pressure...so the water pump, impeller, raw water tubing appear wide open.
2) Same drill with the anti siphon lift hose, start engine, raw water pours out again...no problem.
3) With hose water running, engine running, water pouring out of siphon hose, I jam hose end onto mixing elbow...no water exhaust from the through hull....so it's the mixing elbow, right?

Wrong...wrestled the mixing elbow and exhaust gas elbow off...not clogged in either port. Dabbed on the anti-seize thread goop and replaced the elbows.

4) Okay, the exhaust seacock is open...no question, because I got an initial surge of exhaust water out, probably what was left over from shutdown.
5) Is there some way the exhaust water is not able to push down through the muffler, and then back up through the loop and out? I mean it was able to for the last 5 years with no change in muffler, baffle.

I did move the thru-hull exhaust seacock up the hull about 10" because the original was right at the waterline. I worried about back pressuring the exhaust water when motorsailing on a starboard tack.

I think I know what you're thinking...if it all worked before, and you changed something, must be the thing that changed?
The exhaust hose however is on the same set of hangers as before, at the same height above the muffler and above the waterline. It's not that the exhaust water is traveling any higher, it's just exiting the boat sooner.

Do I need to prime the muffler...there's about two quarts or so of water in the bottom of a maybe 6 quart capacity?

I missing something...any suggestions?
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Old 18-01-2016, 07:57   #2
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Re: Raw Water Exhaust (NOT)

Do you have a check valve in the exhaust line? Is it jammed or reversed? Sometimes they are hard to see.
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Old 18-01-2016, 08:06   #3
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Re: Raw Water Exhaust (NOT)

Thanks for plying through my "exhausting" contortions to find the weak link.

No check valve that I'm aware of, or flapper, and certainly nothing that I've added since it was working fine.

I'm going back to the bilge this morning.
Wondering if I just need to keep the engine running a little longer for the muffler water collector to fill up some more before it will actually force the excess exhaust water out through the seacock?
I guess I could just fill up the muffler canister beforehand, huh?
If this is it, I'll be feeling foolish but educated.
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Old 18-01-2016, 09:17   #4
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Re: Raw Water Exhaust (NOT)

Interested in hearing how filling the muffler canister works for you after you try it.

How long did you run the engine before shutting it off. I had a similar problem on a Yanmar 4JH45 - sorta - but it turned out to be bits-n-pieces of the destroyed former impeller that slowed outflow of exhaust water. Interesting that you note it no longer pulls from the strainer though....if you briefly close the inlet thru-hull while it's running, does the impeller suck all the water out of the line, or is it stationary? That initial spurt might be pushing out quick shot of pressure on start, but perhaps the impeller isn't pulling right? Could have been installed a little lopsided, or wrong size, and it's already chewed up? Pretty tough predicament.
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Old 18-01-2016, 09:51   #5
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Re: Raw Water Exhaust (NOT)

Wow, this is like reading my own Captain's Log! I had the identical problem with my Yanmar 3GM30. I went through all sorts of flow blockage troubleshooting. It would seem to work for a while . . . but then NOT work for a while. It drove me crazy. I took all of the system apart, piece by piece to backtrack to find the problem.

Bottom line - it was the water pump. The cover plate was "scored" just enough to degrade the pumping performance. Some days, it had enough "ommph" to push the water through the whole system, then the next day, it didn't. Weird.

The impeller was fine - in fact, brand new.

When you looked at my cover plate, you could see a small series of grooves worn in a circular pattern. The plate is just soft brass (I think). so, to troubleshoot this, I flipped the plate over - - and put the side with the writing inside the pump against the impeller. I first buffed it smooth because the pump number, name, etc, were stamped into the metal - and it was a little rough.

Once I flipped the cover plate over, it pumped great.

I did end up buying a brand new replacement pump (just to be safe) and kept the "modified" pump as a spare replacement.
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Old 18-01-2016, 11:29   #6
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Re: Raw Water Exhaust (NOT)

You indicate that water flows when the hose to the mixing elbow is disconnected, so the raw water pump appears to be working and the heat x is clear. You indicate that the mixing elbow itself seems to be clear as well. So, that leaves the muffler and the exhaust hoses upstream and downstream of the muffler. Mufflers and hoses can clog or collapse and are easily checked. Finally, raising the hose discharge may have meaningfully changed the system hydraulics (if the exhaust hose acts as a siphon). Raising the discharge could actually increase the pressure at the mixing elbow ("back pressure"), even though the hose high point elevation didn't change. So you may want to return the discharge to its original elevation and give it a try.
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Old 19-01-2016, 05:54   #7
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Re: Raw Water Exhaust (NOT)

Many good suggestions...and I took one especially to act on: filled the muffler canister about 3/4 full with water, thinking the engine won't expel water if there's not sufficient water laying in wait to get expelled. It would not explain why water wasn't rising through the anti-siphon lift hose, but it would possibly explain why water wasn't ejecting from the thru hull.

Remember, the boat is in dry dock, so there is no constant source of raw water to the sea strainer to be pumped through the heat exchanger. I'm using a fresh water hose dunked into the sea strainer. And I think that led to part of the problem...when the sea strainer ran dry, entrained an air bolus, and that might account for the anti-siphon lift loop failing to get water past it and down to the mixing elbow.

When I filled the muffler canister and bypassed the siphon loop...hooked hose directly from heat exchanger into the mixing elbow, problem solved. Ran the engine for 15 minutes.

Once in the water, the sea strainer will be always full and air tight, so a constant source of cooling water. Also, I'm disassembling the Vetus plastic anti-siphon to see if it's correctly oriented.

The hoses and Vetus loop are clean and like new, but the anti-siphon spring is facing me outward. And the loop discharge hose does not piss out any water ever...never has. It may be reversed. Ha!

Thanks for the suggestions. I read every day. Appreciate cruisers sense of community.
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Old 19-01-2016, 08:33   #8
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Re: Raw Water Exhaust (NOT)

Quote:
Originally Posted by kmcshane View Post
Many good suggestions...and I took one especially to act on: filled the muffler canister about 3/4 full with water, thinking the engine won't expel water if there's not sufficient water laying in wait to get expelled. It would not explain why water wasn't rising through the anti-siphon lift hose, but it would possibly explain why water wasn't ejecting from the thru hull.

Remember, the boat is in dry dock, so there is no constant source of raw water to the sea strainer to be pumped through the heat exchanger. I'm using a fresh water hose dunked into the sea strainer. And I think that led to part of the problem...when the sea strainer ran dry, entrained an air bolus, and that might account for the anti-siphon lift loop failing to get water past it and down to the mixing elbow.

When I filled the muffler canister and bypassed the siphon loop...hooked hose directly from heat exchanger into the mixing elbow, problem solved. Ran the engine for 15 minutes.

Once in the water, the sea strainer will be always full and air tight, so a constant source of cooling water. Also, I'm disassembling the Vetus plastic anti-siphon to see if it's correctly oriented.

The hoses and Vetus loop are clean and like new, but the anti-siphon spring is facing me outward. And the loop discharge hose does not piss out any water ever...never has. It may be reversed. Ha!

Thanks for the suggestions. I read every day. Appreciate cruisers sense of community.
Anti-siphon valves are the work of the devil in my experience, but then I've had to deal with faulty ones. Consider ditching the spring and piston and running a 1/4" I.D. line from the top of the loop to the cockpit, next to the scuppers. The "access to the atmosphere" well above the waterline accomplishes the purpose of a siphon break, while the occasional squirt of lukewarm water demonstrates you've got a viable cooling circuit. To clean, remove, rinse and restore. Cost: a metre or so of rad hose.
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Old 19-01-2016, 09:52   #9
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Re: Raw Water Exhaust (NOT)

I had something similar. Loooong story short I had an air leak on the suction side of then water pump, sometimes it would seal, other times not. Took forever to find it.
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Old 19-01-2016, 10:22   #10
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Re: Raw Water Exhaust (NOT)

I had the same problem on my 2GM20 after replacing the waterpump impeller, even after putting on a new faceplate, the problem persisted. It only started working properly after I had 'primed' the water pump by disconnecting the pump outlet, filling the strainer with water and slowly tuning the pump by hand so as to 'fill' each lobe on the impeller. After that it worked fine even when I allowed it to completely drain the strainer and hose down to the pump. Very strange!
It was not helped by the fact that in their lunacy, Yanmar place the waterpump on 2GMS with pump body facing aft so to change the impeller, you need to completely remove the pump, God knows what they were thinking! I would like to have a spare handy so that I can change over quickly but here in UK Yanmar have Johnsons hands tied and you cannot purchase the equivalent Johnson model from them, you have to buy from Yanmar at a cost of about 270 ($430) whereas I have seen them available in the US for around $200 from Johnson suppliers, but shipping costs almost doubles that so not an option, shame.
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Old 19-01-2016, 10:39   #11
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Re: Raw Water Exhaust (NOT)

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It was not helped by the fact that in their lunacy, Yanmar place the waterpump on 2GMS with pump body facing aft so to change the impeller, you need to completely remove the pump, God knows what they were thinking! .
Oh man. I AGREE. Total silly engineering move. I got so good at taking my pump on and off, though, eventually it became easy. I also switched over plate screws to stainless steel wing-screws. So I can remove plate by hand - no more stripped heads.
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Old 19-01-2016, 11:43   #12
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Re: Raw Water Exhaust (NOT)

Install one of these Speedseal covers.

Eliminates raw water pump cover wear.

Allows your RW pump to run dry for a few minutes with no pump/impeller damage.

Welcome to Speedseal

Cheers/ Len
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Old 19-01-2016, 13:19   #13
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Re: Raw Water Exhaust (NOT)

1) definitely going to use S/V Alchemy's anti-siphon valve suggestion, and let the small dribble of exhaust water run down the cockpit scupper. I've heard many good folks use this technique to reassure themselves that water is always cooling the engine. I just wasn't sure where to place the hose. Now it will solve two problems.
2) if I could find SS wing screws for the impeller faceplate, I would trade my tiny hex heads out in a minute. Just have never seen them. I guess i could jury rig them.
3) Speedseal had got to be the best answer, although a bit pricey last check. It's on my list.

Thanks everybody.
Into the water, out to the big blue. ..
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Old 19-01-2016, 13:24   #14
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Re: Raw Water Exhaust (NOT)

I sure don't mean to hijack the thread . . . but

Quote:
Originally Posted by kmcshane View Post
2) if I could find SS wing screws for the impeller faceplate, I would trade my tiny hex heads out in a minute. Just have never seen them. I guess i could jury rig them.
.
I found SS wing screws on eBay - something like 50cents each. Figure out your thread size and length and do a search. Easy to find.
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Old 20-01-2016, 09:36   #15
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Re: Raw Water Exhaust (NOT)

Quote:
Originally Posted by kmcshane View Post
First posted question, please bear with me:

Yammer 3GM sitting on hard 6 months, changed and lubed impeller, continuously filled raw water strainer with garden hose water, started the engine...fine.
Raw water initially spurted out the exhaust thru hull then stopped. Quit pulling water from the strainer too.
1) Diconnected hose from the heat exchanger, started engine, raw water pours out without obstruction with a good amount of pressure...so the water pump, impeller, raw water tubing appear wide open.
2) Same drill with the anti siphon lift hose, start engine, raw water pours out again...no problem.
3) With hose water running, engine running, water pouring out of siphon hose, I jam hose end onto mixing elbow...no water exhaust from the through hull....so it's the mixing elbow, right?

Wrong...wrestled the mixing elbow and exhaust gas elbow off...not clogged in either port. Dabbed on the anti-seize thread goop and replaced the elbows.

4) Okay, the exhaust seacock is open...no question, because I got an initial surge of exhaust water out, probably what was left over from shutdown.
5) Is there some way the exhaust water is not able to push down through the muffler, and then back up through the loop and out? I mean it was able to for the last 5 years with no change in muffler, baffle.

I did move the thru-hull exhaust seacock up the hull about 10" because the original was right at the waterline. I worried about back pressuring the exhaust water when motorsailing on a starboard tack.

I think I know what you're thinking...if it all worked before, and you changed something, must be the thing that changed?
The exhaust hose however is on the same set of hangers as before, at the same height above the muffler and above the waterline. It's not that the exhaust water is traveling any higher, it's just exiting the boat sooner.

Do I need to prime the muffler...there's about two quarts or so of water in the bottom of a maybe 6 quart capacity?

I missing something...any suggestions?
If you have verified the raw water pump is pumping and the mixing elebow is not clogged, pull the exhaust hose off the mixing elbow and blow air through it. If you can't you have an exhaust hose, muffler, silencer (if applicable) or through hull blockage. If you can, pull the seawater hose off the mixing elbow again, if it pump water, it has to be the mixing elbow (water in, no water out).

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