New Exhaust Outlet

[Alan Wheeler]

Oooookay.
Firstly, lets get the smoke issue out of the way. I don't think you have a smoke issue. What you are getting is cooling water washing soot from the inside of the system and it's running down the hull. It's going to happen no matter what, it's just that with a system so long as your's, it's going to happen a little faster.
Now on to the system it's self. From what I can see (great photos by the way) I "think" you are safe from water running in, BUT, it could be better and safer yet. So lets start at the beginning.
The exhaust outlet should be cut down lower. Much lower as in say 25-50mm above your loaded water line level. This is so you don't have the uggly black stuff so noticable down the hull. Directly on the inside of the hull, you should have a 90' bend and a riser going straight up to just under the deck level, a 180' bend and the pipe going straight back down again, another 90' bend and the pipe off on the direction it will run through the hull. This run needs to be kept level'ish so as water does not pool and block of the hose. Back to the riser, this acts as a gate to sea water when a wave slams against the hull. Because of mostly back pressure int he system, water can not be forced up the riser and flood the system. It also allows exhaust cooling water to be "blown" out and keep the exhaustas clear as possible. Yousee this as the slow "pulsing or purging" effect of water rushing out and then nothing for a few seconds.
From then on, the system I think will pass. Maybe not pretty, but I think it will be OK. I reckon if you get your guy to do the above at no extra cost, then he can put it down to a learning excersise.

Personally, I don't like commenting on peoples work. I have learn't over the years, there are often reasons why things are done the way they are, that are sometimes not conveyed to the ones like us that then have the freedom of passing judgement.

[seafox]

Thanks for the input Alan, talbot and pwederell.

Alan
Firstly, lets get the smoke issue out of the way. I don't think you have a smoke issue. What you are getting is cooling water washing soot from the inside of the system and it's running down the hull

We still had the soot all over the transom above the waterline when the exhaust exit was at the transom under water though so I dont know? It must have been vapour of some sort to get off the water and all over the rudder and transom.

I am definitely up for a hole repair in the side of the boat and a shift of exhaust exit.

What if I was to get the boat builder to shift the exit to the transom again, just above the boarding platform and have a loop inside the locker where it comes out inside the boat? This was what the old exhaust was like.

[Jeff H]

I completely agree with Wheels on this, but I guess I have to ask,
Why was the outlet moved in the first place? and

Did you give the mechanic permission in advance to relocate the outlet where he did?

Jeff

[seafox]

the mechanic told me that because the exhaust was now going under water it was creating back pressure and hence the soot. He told me to move it to the side. I arranged a boat builder and got the mechanic and boat builder to look at it together. I paid the boat builder and the mech did the work. I have just bought the motor new from the mech.

[Alan Wheeler]

Ummm, not entirely true about the back pressure creating black smoke. UNLESS, this is a Turbocharged engine, which I don't see in the pictures, so I presume it is NA. I won't go over what black smoke is again, (unless you haven't see other topics and want me to). But the one time Black smoke could be produced by restriction is if the turbo is not working to its full potential and thus the fuel/air mix is upset. To enable a restriction of this magnitude by water pressure however, the exhaust would have to be waaaay underwater. Like a good couple of feet or more. And the same would go for NA engines. There is greater chance of restriction if the exhaust system piping is not big enough in diameter for the length of run. It takes effort to blow that water through with the expelled gas.
Now I am not saying that you may not have an issue with the exhaust being excessivly smoky. It's hard to judge that one without seeing it. But a white hull and black exhaust smoke just love each other and will come together. You just won't stop the attraction.
I think there are two way's to attack this layout.
1: you can go back to the original transom layout if that is easy.. But it is always going to be a black gunge issue. The transom sucks smoke in behind it and as you found, the stuff gets everywhere.

What I suggest is,

2: I would leave it all as it is already. I would get a new exhaust outlet cut through the hull, down much lower to the water level. Side mounted is going to be best at leaving as little exhaust residue on the hull and your Mechanic was on the right track with that idea. Ensure that the pipe on the inside rises up as far as you can get it.
I think going this way will be much cheaper and quicker. You maybe able to get the mechanic to do this at no extra charge, than to suggest he re-runs out the entire installation. And if he doesn't want to do it at all, it should not be a major price for someone else to do it.
The guy with the hardest job is the one that is going to block off the old hole and make the repair look good.

[seafox]

Our new outlet 400mm under the first attempt. Bedding Sika still needs to be trimmed.



Other side. comes in and now goes up 90% and has a bend, goes down behind lining and out to rear locker. (other pipe will be removed when the outlet is plugged and fixed)






rear locker

and staight down to wet box.

I have to pay a small amount to boat builder to repair top hole and for the skin fitting on the bottom hole.

Is this better?

[Alan Wheeler]

That looks better. Even if the engine did still soot, it shouldn't coat the hull now.