Through Hull Exhaust

[TheBigJerm]

I've been told this isn't a good idea, yet when I go to the river, I see so many boats with it, can't be that bad can it!! I'm jealous because you can hear the churning of the V-8 engine at idle and then blowing past you on the river. My boat has a 305, which sounds pretty throaty out of water when I am flushing the engine, but in water, it's just a bubble machine. Has anyone ever done this on their SunRunner, or even another boat?

I was thinking of getting them installed on the corners just above the swim deck, of course, only if it will not damage the boat. I have heard the possibilities of the lakes enforcing their decibel rules, but come one, there's flat bottom boats with big blocks and open headers. Really?!?

 

[TheBigJerm]

Through Hull Exhaust

This topic has been started over and over again, and now, yet again. I have an 84' SunRunner with a Volvo Penta 225. I would like to convert to through hull exhaust, if possible, just for cosmetic reasons. I like the look, and love the sound. Now I don't know if my situation is better or worse than any of the other posts I have read, but I am inclined to believe it is pretty simple. Here's my setup, don't worry, I removed the car air filter and breathers.

My idea is that I can run the exhaust manifolds straight back and through the hull, rather than having them divert down.

 

[captmello]

Re: Through Hull Exhaust

We can't see your transom so we don't know if that is an issue. However, you'd have to pull the engine to remove the Y pipe and plug the hole in the transom shield. Doesn't seem worth it to me.

 

[Bondo]

Re: Through Hull Exhaust

Now I don't know if my situation is better or worse than any of the other posts I have read,

Ayuh,... Welcome Aboard,.... Your in pretty Good shape....
The Simplest way is to project a straight shot off the risers thru the transom,...
Drill the holes,+ slip the pipes thru...
Straight pipes are abit cheaper than bent...

I made my own that way,....
Spent the last 10 years redesignin' to quite 'em down....

 

[JustJason]

Re: Through Hull Exhaust

As Bondo and captmello have said. It's alot of work for no return, and in the long run the constant noise isn't worth it and is going to annoy your fellow boaters.

Sure it's pretty neat when a high end Fountain or Donzi rips right past you.... and keeps going....
But when your in the chair, and your driving a bargain barge, the noise just stinks. If your really intent on doing this, look into a captains choice exhaust system.

While your back there fix your fuel line the proper way, and get those batteries in some battery box's and make sure they are bolted down good.

 

[rjlipscomb]

Re: Through Hull Exhaust

This topic has been started over and over again, and now, yet again. I have an 84' SunRunner with a Volvo Penta 225...

Just having fun with you, but how is that little 225 pushing that big 84 foot SunRunner? (84' vs '84)

 

[wca_tim]

Re: Through Hull Exhaust

What you're talking about will work just fine. It is not really that much work compared to many other things we do to our boats.

You'l need a 4 1/16" inch hole saw for your 1/2 in drill, 3m 5200, exhaust tips that install through the transom, flex hose to reach from your risers to the tips and double clamps for each connection.

Assuming your exit will be fairly near the waterline, you'll need tips that incorporate flapers inside or to instal rubber flappers on the outside. You'll also want the flange angle on your tips to be consistent with the angle that the flex hose will meet the transom. You can either pull everything apart to take the y pipe out or cut them back out of the way and seal them off temporarily with 4" pipe caps (rubber, clamp on from the hardware store)

After you cut the holes, seal the exposed wood carefully with thinned resin or epoxy for good measure and then later when you install the tips, seal them in with 5200.

Note that you probably have enough room to run small inline clamp in mufflers between the risers and the transom or may want to buy exhaust tips that incorporate good mufflers. The majority of people like a nice throaty sound to the exhaust, very few like obnoxiously loud...

mufflers, stainless tips etc.. are not cheap, but if you look you can often find used ones for less... since their stainless, you can clean the up...

Hope this is helpful

 

[TheBigJerm]

Re: Through Hull Exhaust

Just having fun with you, but how is that little 225 pushing that big 84 foot SunRunner? (84' vs '84)

Lol, nope just a 21 foot boat.

 

[TheBigJerm]

Re: Through Hull Exhaust

We can't see your transom so we don't know if that is an issue. However, you'd have to pull the engine to remove the Y pipe and plug the hole in the transom shield. Doesn't seem worth it to me.

All this time that I thought about running it through the hull, I never thought about the existing exhaust system, and having to remove\plug it. Your right, it isn't worth it, just something to look for on the next boat!

 

[TheBigJerm]

Re: Through Hull Exhaust

As Bondo and captmello have said. It's alot of work for no return, and in the long run the constant noise isn't worth it and is going to annoy your fellow boaters.

Sure it's pretty neat when a high end Fountain or Donzi rips right past you.... and keeps going....
But when your in the chair, and your driving a bargain barge, the noise just stinks. If your really intent on doing this, look into a captains choice exhaust system.

While your back there fix your fuel line the proper way, and get those batteries in some battery box's and make sure they are bolted down good.

Yea this wasn't too long after I bought the boat. I took it to a shop and had the engine overhauled, now it hauls a**, lol, 40 mph +, according the always accurate speedometer on the boat. The fuel line, air filter, water fuel separator, ignition, coil, oh and battery boxes, are all new! So most of the stuff in the picture is history. As a matter of fact, first time I took the boat out, when I got it, because it was "turn key (my a**)," the fuel line busted on me, wasn't thick enough.

 

[JustJason]

Re: Through Hull Exhaust

What I had meant by the fuel line is that I hope it's not rubber. It should be steel line between the fuel pump and the carb. You should also get rid of any teflon tape on the fittings because ethonal with eat the tape up.

 

[havasuboatman]

Re: Through Hull Exhaust

Don't forget that there is a minimum riser height requirement that you need to follow for thru hulls. There is also a minimum exhaust hose slope you need to follow.
The top of the exhaust risers must be a minimum of 13 inches above the water line of the boat when it is fully loaded.
And you need at least a 10 degree slope of the exhaust hose for the first 18 inches from the engine. 3 degrees after that. That's about 2 1/8" drop per foot and 5/8" drop per foot respectively.
If you don't follow that formula you are going to have water ingestion issues.

 

[ezmobee]

Re: Through Hull Exhaust

I'm going to move this to the I/O forum as it isn't really specific to Sunrunner hulls and you'll get more views.

 

[Philster]

Re: Through Hull Exhaust

Boat type doesn't matter in most cases. The engine/outdrive type matters.

If your engine doesn't have valve overlap, your just run the exhaust from the risers towards the transom and exhaust hoses to the transom, then tips out the transom.

If your engine has valve overlap, then water reversion (exhaust moisture creeping back into the cylinders from the momentary sucking created by valve overlap) becomes a big problem.



You need to look around places like Eddie Marine http://www.eddiemarine.com/

And CCP http://www.cpperformance.com/

 

[Philster]

Re: Through Hull Exhaust

Yeah. Before getting into thru-hull exhausts, google "water reversion" and you might never consider a thru-hull again.

I have a thru-hull exhaust, but there are only two (very expensive) ways to have an open thru-hull exhaust without seriously risking water reversion on a Merc 502 (whose valve overlap means the engine is actually sucking BACK during part of the exhaust cycle.) All engine risk it, but some with more aggressive valve/cam timing risk it even more.

Eddie Marine (manifolds/risers) and CMI (true headers) have enough rise and slope along with placing water injection closer to the transom that they minimize reversion risks (but you never are guaranteed it won't happen).

So... whether you tackle it on a current boat or seek it in a new(er) boat, make sure the boat you buy was done right, and that the thru-hull exhaust has the right rise/slope to the headers/risers/whatever and that the water enters the exhaust far from the engine... and the closer to the transom the better.

 

[wire2]

Re: Through Hull Exhaust

...... You should also get rid of any teflon tape on the fittings because ethonal with eat the tape up.

No, it won't.
PTFE (Teflon) is resistant to ethyl alcohol, a.k.a. ethanol. See the Chemical Compatibility Guide here;
http://cool.conservation-us.org/coolaic/sg/bpg/annual/v11/bp11-33.html

 

[JustJason]

Re: Through Hull Exhaust

No, it won't.
PTFE (Teflon) is resistant to ethyl alcohol, a.k.a. ethanol. See the Chemical Compatibility Guide here;
http://cool.conservation-us.org/cool...1/bp11-33.html

Apparently you do not work on boats, have never done a boat side fuel system test, or repaired fittings that don't always drip fuel out, but suck air in instead.

That website may claim that pure teflon, the actual material teflon all by itself, may be resistant. But there is a big difference between resistant and proof. It's like saying XYZ fabric is fire resistant, but ABC fabric is fire proof. Big difference.

Trust me, the fuel eats the tape.

 

[Utahboatnut]

Re: Through Hull Exhaust

In addition this would be done for sound/looks only. The thru hull won't give a 305 any more power or torque. I think I would put the $ into some fenders for that trailer, and yearly maint. and gas.

 

[haulnazz15]

Re: Through Hull Exhaust

They do make a special pipe-tape for use on fuel line connections though. Teflon won't usually last, and most of time still drips fuel.

 

[havasuboatman]

Re: Through Hull Exhaust

I have installed many, many, brand spanking new right out of the box Mercruiser motors. From 377 cid small blocks to 1025HP big blocks. And never have I replaced manifolds, or water injection, or anything else to keep them from ingesting water. It's not hull type or engine type. If you follow the formula for Riser height, Exhaust angle and drop ratio You Don't Have That Problem. It's people who don't know what they are doing that screw things up. Other people who buy those screwed up boats assuming that because their exhaust has a problem, that all of them are junk.
So these clueless people get on sites like this and spout B/S about " I'll tell you about thru hull"
Philster, you are cluless about thru hull. CCP or Eddie marine, huh? Have you ever heard about a thing called a resonator? That's what you use, when you do an exhaust wrong, to correct the problem.
10 years and thousands of boats built by me for Nordic, Advantage, Sleekcraft, Magic, etc., etc.
That's how many perfectly working, stock manifold, open exhaust, 502 cid motors I've done.
Dont' bad mouth thru hulls in general just because you didn't put yours in right.