Side Exhaust vs. Out the Back

[JohnD]

Thought I'd post this here for general discussion. I'm about 3 weeks out from starting my Diesel conversion, unfortunately timing of yard and motors pushed things back.

Anyway, here's the topic:
I've got a 1972 B35 with gas and 3" exhaust out the stern. I'm installing 3126 Cat's and will be changing the complete exhaust over to 6" per spec for my motors and I'll be using an inline muffler.

My Options are:

1) Keep the current config and run out the back of the boat. May be a little quieter than out the side, but greater stationwagon effect bringing fumes into the cockpit.


2) Modify and exit the exhaust out of the side of the boat & if so, how far up from the stern? I'd expect this modification to cut down on cockpit fumes, though may make the boat "sound a little louder".

I'd be interested in hearing the thoughts and opinions of others.
(Please vote above).

Thanks,
JohnD

[alano]

John, can you use the fiberglass diverters (assuming they're there), I know they fit over 5" bronze flange. They do a good job pushing the exhaust into the slipstream. If they're gone, I think the outfit in Australia that makes Caribbeans still produces them. Alan.

[JohnD]

Thanks Alan, The diverter's you mention are the ones screwed over transom outlet? If so I have them but one is chipped, but could be patched.

I was wondering if anybody had switched from back to side and what thier thoughts were?

Thanks,
John

[Carl]

Interesting post, I will be watching as one complaint I always seem to get is the fumes are killing me... cough... cough... once a person starts, it becomes a chain reaction and I want to toss them all off the boat.

Not running on many boats with side exhaust makes it hard to make an educated guess, but I like the way the exhaust looks and sounds comes out the transom. Plus I feel being able to guage the cooling water coming out the exhaust allows me a heads up on any problems.

On the exhaust flaps I tilted them outbourd ( a tip on the Boating show) to direct exhaust outwards, does it work, how knows but it made the wife feel better that I did something.

[bertramsupermex]

Take a look at the side exhausts that Carl from Elite Marine installs. He has done several B31s and the owners love them. I can't speak to them yet as the boat is still having restoration work completed.


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[mike ohlstein]

Interesting post, I will be watching as one complaint I always seem to get is the fumes are killing me... cough... cough... once a person starts, it becomes a chain reaction and I want to toss them all off the boat.

Good idea.....toss 'em off the boat.

What Ray Hunt hath prescribed, let no man put asunder (or aside....as the case may be).

[Capt. Mike Holmes]

I have a transom platform, and ran extensions on the exhaust (rubber hose, wire reinforced, with flaps on the ends) to the back of the platform. Keeps the exhaust from blowing water into the cockpit when I crank up the Cummins, helps keep the smell out of the cockpit, and I can see the water coming out of the exhausts from looking over the transom. It makes the back end of the boat look like a hopped up '57 Chevy, 327 and dual exhausts. Sounds good, too.

[Hyena Love]

How about vents or ducts to direct more fresh air into the cockpit to break some of the vac.?

[JohnD]

I had posted the same question on the B33 board, just to broaden the audience. Several there had added side exhaust as part of their conversion and are happy with the results.

Roland, nice pix!!! I love what your doing with SUPERMEX.

After hearing some discussion about the side exhaust, I'm going to do it if the budget allows. I should be getting pulled in the next week and once I get things apart, I'll know what I have to do and then can add the things I want to do.

One thing I have decided is that whether it's out the back or side, the generator exhaust will dump out of the same hole as the port side exhaust.

Can't wait for the fun to begin.

John

[Sean B]

I have a transom platform, and ran extensions on the exhaust (rubber hose, wire reinforced, with flaps on the ends) to the back of the platform. Keeps the exhaust from blowing water into the cockpit when I crank up the Cummins, helps keep the smell out of the cockpit, and I can see the water coming out of the exhausts from looking over the transom. It makes the back end of the boat look like a hopped up '57 Chevy, 327 and dual exhausts. Sounds good, too.

Hey Mike that is one hell of an idea, I think I'm going to try that one out. I bet it keeps the soot off the transom too? That would be my main motivation, and also to keep the fume nazis in the cockpit from complaining (I hate that too).

Any advice on the project? I'm wondering if my exhaust outlet flanges are big enough to accept a hose and clamp. I'm talking about a B33 here, but that really shouldn't matter.

Great idea, thx

[Sean B]

... and I want to toss them all off the boat.

Hey now that is a Florida thing, don't you yankees start stealing all our stuff

[Carl]

Toss'em off the boat is a universal thing!

Eight people on the boat ALL day long, fishing, cruz'en, sight seeing, dock n dine then a 2 hour ride back to the dock at night and the last half hour someone detects fumes, within five minutes I have 7 people hanging their ass over the transom telling me how bad they are ....how its making them sick. Toss 'em

[Capt. Mike Holmes]

I saw this done on several other boats first, I think at least one was a factory job, maybe an Orca? Also an old timer I respect very much told me he used to do it a lot on boats he worked on. I'm not sure how you'd attach the extensions to a factory exhaust flange, I ran fiberglass pipe through the transom when I redid my exhaust in the repower, and left enough sticking out to just hose clamp the extra lengths of rubber hose to, then supported them off the platform, also.

[Sean B]

Thanks Mike. I love the idea but I don't think I have enough flange to do it. The ass end of my boat looks like this



There is no way I have enough room to slip hoses and clamps over the ends of those flanges. Slipping something inside would be a restriction so I don't want to do that either.

Any bright ideas?

[dougl33]

Sean,

With all that black and white you must be the Bertram police!

[Capt. Mike Holmes]

Yeah, doesn't look doable. I saw a 33 once that had just been repowered gas to diesel, and I remarked at how small the exhausts out the transom were. My old timer buddy who knows everything boating told me some Bertrams had a split exhaust, with the largest portion going out under the hull, and just a smaller pipe out the transom as a hedge against back pressure, I think. Never saw this boat out of the water, though.

[dougl33]

Mike,

All gas powered 33's (and some diesels) are set up that way. Bertram called it their velocijet exhaust system. The boats are very quiet. There are what look like mail slots about a foot under the rails (not under the hulls) near the stern of the boat.

My 1981 28 was set up the same way, though I don't know if all 28's were set up this way.

[Capt. Mike Holmes]

This one had the marinized GM pickup diesels, and it very very quiet.