1989 Webbcraft Exhaust

[dausbury]

I have an 89 Webbcraft that I am about to get on the water and want to make sure that I have the exhaust set up correctly. This boat has two sets of exhaust tips, one set exits the engine compartment into a set of boxes built in to the hull under the swim platform then another set of tips exiting the boxes. The boxes under the swim platform have two 1/2" drain holes in the bottom. The inner exhaust flappers that were inside the inner tips were burnt out when I got the boat and the drain holes in the boxes were plugged with rubber hose around a wall anchor. I originally flipped the inside tips around so the exhaust hose would go on the angle cut end and installed rubber hose clamp style flappers on the ends of the inner tips inside the boxes but I was nervous that they would not function properly inside the boxes when the boxes had water in them. I have ordered a set of replacement inner shutters to install in the inner tips and plan to remove the rubber flappers and reinstall the inner tips with the shutters installed. I am looking for some advise on what the proper set up should be. Should the shutters go in the inner or outer tips? Should the holes in the boxes be open or plugged? What function do the boxes serve, I am assuming noise reduction? Should I try to rig the exhaust to go straight through the boxes to the outer tips somehow? I have attached some pictures of the exhaust system with the rubber flappers installed on the inner tips. I am installing a rebuilt 454 and do not want to risk getting water injestion.

 

[jerryjerry05]

Re: 1989 Webbcraft Exhaust

Where does the small hole drain to?They should probably be plugged while in operation.
The boxes are like a muffler.How is the manifold/riser setup? Any possibility of flappers in that section?Two sets of flappers might work.
If you use the angled tips on the outside then for sure use the flaps on the inside.Anything to stop the flow back into the motor.Post some more pics of what your putting in.J

 

[MahtyMaht]

Re: 1989 Webbcraft Exhaust

My stepson has an '88 7 meter Velota by WebbCraft - looks the same as yours - His stainless exhaust tips have angled oval plate flappers inside of them. Very simple, very bullet proof.

 

[dausbury]

Re: 1989 Webbcraft Exhaust

Thanks for the info Mahty Maht. Are the flappers in the inner tips coming out of the engine compartment or in the outer tips exiting the noise reduction boxes? Also are the two 1/2" holes in the bottom of his noise reduction boxes plugged, partially plugged or open? Does he have angle cut tips exiting the rear of the noise reduction boxes? If so does he have a problem with his outdrive hitting them when trimmed all the way up?

 

[MahtyMaht]

Re: 1989 Webbcraft Exhaust

No, the outdrive won't actually contact the external tips when trailered up at either lock. I must say, though, that after installing the engine and outdrive, fixing a bunch of other stuff, trim switching among them, the first time somebody else was there to hit the switch, and I was back there watching, the drive got close enough to an exhaust tip to make my sphincter slam. The flappers are actually in the external tips. There are no drain holes in the boxes that house the tubes where the tips mount.

 

[MahtyMaht]

Re: 1989 Webbcraft Exhaust

And you do NOT want water in those boxes. The inside is rough as a cobb, not gelcoated or otherwise finished. It's why the tip flanges get sealed on the outside end of those boxes. My understanding of exhaust tube geometry for this rig is that there should be a minimum 6 degree down angle on the exhaust tubes from elbow to transom, but that's a parameter established by the boat manufacturer. You could conceivably reduce it messing with aftermarket exhausts, but that really seems unlikely. I think it's that angle that prevents reversion, (engine driven phenomenon), and the flappers prevent incoming stern waves from washing up the tubes with sudden throttle cuts, etc. I have read that if you had a really agressive cam with lots of overlap, you might be able to start some reversion problems, but this is not based on my experience, because I don't have much - just huge amounts of indiscriminate Merc and boat research, driven by my fear of avoidable catastophic outcome, after I agreed to take a crack at fixing my stepkid's boat, and ended up replacing the engine, propshaft, and undoing lots of vandalistic maintenance. I don't see holes in the pic of the box - where is it?

 

[MahtyMaht]

Re: 1989 Webbcraft Exhaust

I'm feeling kind od dense all of a sudden - My exhaust set up is different, in that it has only one set of tips - the externals. At the transom there are just a couple of fiberglass trim rings. The tubes go thru them, but they are otherwise not attached. I wonder if that's something some PO did on your boat, my boat or a factory design change?

 

[dausbury]

Re: 1989 Webbcraft Exhaust

Thanks for getting Back to me. As you can see in the pics attached my set up looks factory. The inner tips come out of the engine comparrment and into the boxes under the swim deck. Then there is a second exiting the boxes. The boxes have two half inch holes in the bottom. You are correct the boxes are not gel coated on the inside. I am really not very confident on how to set up the. Flappers or weather or not to plug the holes.

 

[dausbury]

Re: 1989 Webbcraft Exhaust

Allthough the boxes look factory I am not sure they are because the out drive will break the tips off if not centered before hitting the trailer trim. I have already dented them up twice. Are you saying that your velota has the same boxes under the swim deck, but the exhaust tubes go all the way through them to the rear tips? If so what purpose would the boxes serve?

 

[jerryjerry05]

Re: 1989 Webbcraft Exhaust

Muffler.J

 

[MahtyMaht]

Re: 1989 Webbcraft Exhaust

I think Jerry is probably right that they are mufflers, maybe they're swim deck supports, too. My 4" rubber exhaust tubes attach at the elbows on one end, external tips at the other. My tips have 1/2" holes, too, but they are covered by the exhaust tubes, so they aren't an issue. It would seem to me that you would NOT want those holes open to the inside of the boxes, as that would allow the the engine to discharge exhaust water into the boxes. I don't see how you access the hose clamps inside the boxes with your set up.

 

[MahtyMaht]

Re: 1989 Webbcraft Exhaust

It occurs to me too, that since the flappers are supposed to act like a check valve, allowing rapid water movement in only one direction, if there are flappers inside the inner tips, and they are reversed, they may be, restricting water flow out of the tubes. Bad, bad, bad.