Underwater Through Hull Tails
 

Has any used through hull tails that terminate under water? I am talking about dry to the tip double wall tails that use the transom rings and round rubber gaskets (attached pic).

I am using KE cast headers that end very close to the flywheel housing mating surface of the block. With them ending this far back it only allows enough room to make a quick 90 deg bend off the header flange and then a 12” vertical drop and then another quick 90 deg bend to exit the transom. The tail pipe would be about 75% under water in the factory cutouts. The distance between the exhaust header flange and the transom is so close I don’t think there would be enough room for a standard transom mounted tip and 4” rubber hose to connect to the “S” pipes lower 90 deg bend.

I have thought about using silicone in the gap around the pipe and transom hole and then use more silicone to seal the gasket.

My concern is will this seal or is this a problem waiting to let go and risk sinking the boat? This boat is usually pulled out at night with a few 4 day long trips in the water per year. Has anyone installed these trim rings and gaskets below water with a no leak seal?

Thanks for your thoughts...

Here is what the mocked tails looks like on the inside and then the out side with the old tips.

It will NOT seal !!!!!!!!!!!!!!!!!!!!!!!!!!!!

wouldnt even make it off the trailer !!!!

Are the oil tips in the same location as before?

I mean old tips

Lol,,i was wondering what oiltips are .HAHA:grinser010:

Hey Jon,

I wouldn't trust those flanges at all.

What about going out the sides?

Tell me he wants to use plastic pipe!

I hope not !! LOL :party-smiley-004:

Yes, I would like to use the factory tip location so I don't have to fill and re-gel. The factory tips did have welded flanges, so they are much safer.

Come on man! That's an insult... :crazy:

Is the plastic a mock-up?

Thanks for your input Bill and everyone else that put some serious thought into this. I have contacted a few of the major power boat suppliers (Eddie Marine, IMCO, CMI, and Teague). Surprisingly enough with very mixed feelings! :eek:

Ya, notice post #2 (pic of mocked up tails).... :grinser010:

sorry long day! I overlooked the mock-up statement

I would definately not use those rubber seal things!

I would use standard exhaust thru hull outlets, with exhaust flappers, and have someone make up custom stainless down pipes in an exagerated S shape.

This way, you could bolt the down tubes on to the rear of the KE headers, and only have one rubber hose fitting where they meet the tails.

Nordic will make these for you if no one else will , and polish them.

Your motor looks so trick... why would you even think about doing it any other way?

Chris

Here is what Nordic made for my motor, with the newer corner exhaust outlets:

Chris

Thanks Chris,
It sounds like Standard tips are the only way to go. I will mod my mockup to allow for more room between the transom and use a short piece of rubber hose.

Would 1/2" gap between the tails and tips (portion the rubber hose would cover) be enough to absorb vibration and slight movement?

Your 600SCI with sport tubes looks great!

Jon

1/2 inch is perfect.
I have done it with 1/4 inch clearance, and no problems after 3 seasons of boating.

I don't know about your motor, but mine is solidly mounted... hence no movement.

Chris

Good! That will give me a little extra room. What is the minimum distance the rubber hose should slip over the tip and then on the tail? I am thinking just enough to get two hose clamps on each end. The clamps are 1/2" wide, so maybe 1 3/16" slip over on each side?

My motor will be mounted with billet aluminum pedestal mounts. They should be more solid then the mercruiser rubber isolated ones.

Jon

You are correct... Just enough to get a couple of hose clamps on each side.

Can't wait to see a picture of your motor in the boat.

Chris

P.S. I always mount mine with anodized billet aluminum also... color matched to the other stuff on the motor and boat. If you look at the bottom center of the picture I posted, you can see the polished, under engine, motor cradle, and the red anodized spacers, and stainless bolts.