Exhaust Thru Hull going from 4" to 6"

[fishlook]

forgive me for new post, I've been searching the old threads but can't seem to find what i'm looking for..............

I am going from 4" exhaust from my old 454's to 6 inch for my new 3006bta's. As I lay awake in the middle of the night I'm thinking I'm going to simply expand the 4 inch hole in my transom to 6inch (6 1/8) and use fiberglass exhaust tubing extending 2-3 inches out the back and glass it all in.......from the fiberglass exhaust tubing I will go back to the engines with exhaust hose, fiberglass exhaust tubing, mufflers, etc.......

How does this sound for a plan? anyone have any photos or better ideas? The 454 exhaust had a SS exhaust flange on the transom that has been removed.

[CaptPatrick]

Jay,

Have a look at Hancock's exhaust system

Also so a brief discussion on surge tubes that was posted back in September

[fishlook]

very nice thank you.

so with my 300's you say mufflers and surge tubes would be ideal?

I see your genset exhaust running to the back but don't see it coming out of the transom? did you tie it into the engine exhaust?

did you manufactor the oval exhausts or buy them? what size are they? how far out do they come from the transom.

I'm reading past posts now to get smart on surge tubes.....

[fishlook]

also.... did you move the mufflers and exhaust outboard to make room for fishboxes or something?

[JP Dalik]

by moving the exhausts as far outboard as you can you make room for fishboxes or storage below the hatches. there is a muffler made by centek called a centubular muffler. its been used in a few boats up here including ours with good results.
i think primex may make a a smaller diameter muffler as well.

good luck i can post some pics if your interested

[fishlook]

pics would be great. thanks

[wmachovina]

centek also makes an oval muffler that fits outboard of the stringer is only 7-8 inches tall(fits under cackpit sole and is much cheaper than the tubes. I put 5 inchers in (250 cummins) but they make a 6 incher too. fives were about 300 ea. Bill

[JP Dalik]

These are what I could find Hope they help.

[ed c.]

J P Dalik, when did you steal my 2" scupper guards.

[JP Dalik]

J P Dalik, when did you steal my 2" scupper guards.

A little bird told me I could build simple scupper guards if I went to ACE and picked up some 2" pipe.

The little bird didn't tell me I'd spend 6 hours grinding, glassing and faring them into the transom.

I hate that f'en bird

[Bob H.]

Fishlook, After hearing all the boats at the Pt Judith rendevous, the big mufflers seem to be overkill, moved mine outboard, tubular exhaust, got two big fishboxes, I should have listened to JP and others from the get go...

[coolair]

see if you can get John to post some pics of real cowboys exhaust, its pretty slick.

[fishlook]

Bob H.-

so no mufflers and straight out. any sound proofing? are you happy with the noise or lack of?

jay

[JP Dalik]

What your looking at in both Bob's post and mine is the muffler. Not a straight pipe. Little more noise at idle, not much difference running. But then again I can't tell what's engine and what's exhaust even with all the sound proofing. Dem turbos sure are loud

[fishlook]

do you have dorade vents - i'm reading that helps noise levels?

[Bruce]

Dorade boxes in the side of the hull reduces noise only because of the location. They are really designed for keeping water out of the engine area by catching any spray and draining it out, not noise reduction.

Reducing noise to its minimum requires sealed insulated engine boxes and outside air intakes, nothing that opens into the cockpit.

There isn't anything that will totaly reduce turbo whine but you can get it down to where at cruise speed a conversation between the engines boxes at normal speaking levels is possible.