Yanmar 3GM30F Water Heater

Apr 22, 2011
865
Hunter 27 Pecan Grove, Oriental, NC
Ralph, I have seen photos of your engine compartment before, and every time I view them, I seem to fall into a deeper state of depression, knowing that there is no way my engine will ever look like that. In the future could you preface your posts that include a photo of your engine with a warning something like this: !!Be aware that some viewers may find the following photo disturbing!! Thanks
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
... They were the same size ID measurement. They fit on every other fitting/connection in the boat. With no leaks, even to the old Water Heater. The only "new" add on is the Water Heater, same model Seaward S600. As I can't change the welded fittings in the back of the Heater and the next size "down" in Heater hose won't fit at all, my only option I can see is take up the slack on the fitting. ...
Might check with the factory. MAYBE they sent a mm size heater- if they make them??? My Beneteau had a couple places where they packed in the caulking to fill the gap between the hose and a thruhull of a lesser size. Galley sink thruhull.
 
Apr 11, 2018
71
Hunter 340 Dowry Creek, NC
My '99 340 has the same issue, a leaky old S600. It's grown gradually worse over the last year. The leak appears to be from corrosion around more than one of the fittings. I concluded it wasn't worth the probably futile effort of trying to repair so have ordered a new Isotemp SPA to replace it (on sale at Fisheries Supply). I plan to start on that project, which includes new PEX, potable water pump, and strainer, next week. Were I not going to replace the heater now, I'd keep it clean and do a bypass per jssailem's diagram.

One thing I've noticed is that when the old heaters were installed, the heater hoses were invariably run over and down around the engine's alternator. They prevent it traveling the full length of its belt tensioning takeup. Part of this project is to lengthen the heater hoses enough they can be routed away from that area. I like the idea of putting in Ralph Johnstone's isolation valves, too, so I think I'll add that to the new setup.
 
Sep 26, 2008
546
Hunter 340 0 Wickford, RI
Nichole,
I just finished the same exact job as you, same S600 (as original in 2000) and YES, the rear heat exchanger inlet and outlet fittings are just that little bit smaller in diameter. And I have the same 5/8 inch heater hoses from the engine to the water heater (I replaced all my hosing about 4 years ago) and they fit tight to every fitting on the boat but the Water Heater!

The first thing I noticed was the ease at which the hoses slid over the fittings and flopped around. To easy in fact!
I'm assuming your boat is in the water because you said you have a leak at both fittings, so you've tested it. Mine isn't in yet.

Your teflon tape idea is what I did to make a more snug fit. But what I did was I used was a tape called "Blue Monster PTFE Teflon Tape". It's thicker and rubbery to the feel, designed for a wider gap thread.
I wrapped the fitting(s) from the inside edge of the tank, to the edge of the Bell End. It's about 2 inches long on each. I wrapped enough to make the entire fitting a little less in diameter than the Bell. The hoses slid on rather tight and I used 2 clamps on each.
There's just about enough room for two, but they fit.

I can't tell you if they will drip or not when hot antifreeze starts flowing through, but in a couple of week will be the real test.
But I think you are right in using teflon tape to take up the difference, but not the "white" tape. The Blue Tape ( more costly if I remember right, $4.00 vs 0.99) but matches rubber hose to rubber and should be a leak proof fit.

Why they made the fittings smaller in diameter I'll never know. But my guess is $$$. And it may even be the hose manufacturer decreasing ID size for the same reason.

Good luck with the final step. I know it's a lot of work and time removing the seat top and sliding it out of the way in that area. But I'm 99.99% sure this fix will take care of the drips.

Lets us know.
 
Jan 12, 2019
99
Hunter 340 Narragansett
My thought is that this, smaller sizing as to the new equipment, is more normal than not. I won't be able to tackle the process of removing and repositioning the Heater to get to the hoses this week but it's on for the weekend.
The thicker rubber teflon tape seems to me to be a very good way to go. So I'm going to give that a try.
The difference in fittings to hoses, is so minute that it hardly seems it would create a problem. But yet it does!
Thank you all for the help and ideas.
I know the Water Heaters have to go at some point, from age, but the lack of postings makes me think maybe it's in the Winterizing I'm doing that's leading to the problem, as others don't seem to have any Water Heater issues. Maybe not enough antifreeze in the tank?
I get some coming out of the drain valve when I do winterize but maybe there's not enough in the tank for the inch or so of water left on the bottom. I drain the tank at the end of the season and add antifreeze directly into the tank. It can be a bit messy but it is easy enough.
And I thought that would be better than leaving the tank full of water-antifreeze mix and no place for expansion.
Time to rethink this whole process I guess.
 
Sep 26, 2008
546
Hunter 340 0 Wickford, RI
Nichole,
An update to your original question and some pictures. My boat is in the water and I had the engine running while installing the Bimini to check the coolant flowing to the water heater. The Thicker Teflon Thread Tape does work, no leaks due to the reduced size of the inlets on the heater.
Don't know if you have redone yours or not but thought you would like the update. The pictures are a little dark as I wasn't about to remove that 6 foot wooden seat bottom again! But you can see the double clamps and dry hose.
Good luck with your project.
See You on the Water.
 

Attachments

splax

.
Nov 12, 2012
692
Hunter 34 Portsmouth
I'm not sure if it is an issue, but the antifreeze may degrade the tape, so checking it periodically my be advisable.
 
Sep 26, 2008
546
Hunter 340 0 Wickford, RI
Splax,
Believe me, I plan to check them often. It's hard to see from the photos and just as hard to see with the naked eye, when my head is stuck behind there, but the tape is actually only on the 2 inch part of the tapered fitting. Up to but not over the Bell end or out past the end of the hoses.
The tape says it's not effected by distillates, but I'll be checking constantly.
Like I stated earlier in this post, they just had to make that fitting just that little bit smaller. Couldn't leave well enough alone by making it Match the ID of the hose. $$$ I guess.
Thanks for your concern. I'll keep you posted of any other outcomes.