300 promax tuner

[Varmint]

So i finally had time to take clamp and tuner off my old 300 promax mid, for paint. Of course broke 2 10mm bolts/fasteners, 3 ez outs, ended up just drilling out to 3/8" and looks like plenty of meat left to re tap and/or helicoil. Sending it out for glass beading, as it had a bit of saltwater use. Be putting my 250xb with 300 heads and 300 ignition ecu on it. Should i shorten the tuner ? Or just leave it stock ?

[ghost28]

Leave the tuner portion itself and cut the liner at the casting line....or buy a taylor, hydrotec, bobs, tuner and save the tume of cutting....

[Varmint]

I should have said liner,I bet it's loud,lol
Leave the tuner portion itself and cut the liner at the casting line....or buy a taylor, hydrotec, bobs, tuner and save the tume of cutting....

[One Oldman]

They say they are loud. Changing exhaust location should help if you are going to run OTH props.

[ghost28]

mine is not that much louder in my opinion...a lot more tinny sounding at idle....

[Varmint]

it's on my xb2003 allison,I usually run choppers,but that much motor won't care,lol
They say they are loud. Changing exhaust location should help if you are going to run OTH props.

[Varmint]

been reading that it doesn't really give 'em much performance gains,,it's easy enuff to cut on bench ,with 14" chop saw,just gotta heat/remove water tube retaining bolts,I have to cut water tube anyhow,it is a 20" can,but had a 5" spacer from factory,it was the stbd. unit,from twins. It appears that merc. used a 25" shift shaft and water tube,whereas I have found 5" extensions before in 2.4/2.5 25" spacer kits. I already ordered correct studs and gaskets,shift shaft for it,to load my TM Gen 1 onto it.
mine is not that much louder in my opinion...a lot more tinny sounding at idle....

[One Oldman]

So Varmint, what pitch prop are you going to start off with on the XB?

[One Oldman]

it's on my xb2003 allison,I usually run choppers,but that much motor won't care,lol So what pitch prop are are you going to start out on with the XB? I'm looking hard at the Eagle 3s and 4s or maybe a Hoss all in 32.

[Varmint]

dunno,I have a 30 bravo and a few 29/30 choppers

[Varmint]

what boat /motor do you have ?
So what pitch prop are are you going to start out on with the XB? I'm looking hard at the Eagle 3s and 4s or maybe a Hoss all in 32.

[Varmint]

boat ran good with a cut 28 hill big ear,and a 26 pro et with a 2.5, I dont have a 3l sporty,was gonna' cone a TM gen 1
dunno,I have a 30 bravo and a few 29/30 choppers

[One Oldman]

what boat /motor do you have ? Mines a Shadow VT200. Motor will be 250XB with a few mods. I'll probably have to start out with a standard coned lower unless I just run up on something I like. I don't know my weight yet but think most likely between 800-900#.

[Varmint]

Mines a Shadow VT200. Motor will be 250XB with a few mods. I'll probably have to start out with a standard coned lower unless I just run up on something I like. I don't know my weight yet but think most likely between 800-900#.
I have had shadows , my red one ran low 90's with a bridgeport and 29 srx, buddy mac runs 100+ with a 2.4 BP, i'd think she would rip with a good chopper, 30p+

[Chaz]

been reading that it doesn't really give 'em much performance gains,,

No ... ehh ?

So how often do you think the motors with full liners , go around and wave bye-bye to one's that have been ..... relieved ;)

[Varmint]

I dunno,that's why I asked ? :)
No ... ehh ?

So how often do you think the motors with full liners , go around and wave bye-bye to one's that have been ..... relieved ;)

[Chaz]

My bad , I thought you made a statement . Theorized from the compilation of your readings ... :smiletest:

"Just" cutting the inner liner will give the exhaust a larger area to expand in before it meets the same "total exit area". There is room on the bottom of the cavitation plate behind the back set of 12mm studs to drill a few .625" holes .
It will be quiet @ idle and move enough air at WOT to be happy .

The tuner leave's a bit to be desired . But if your going to take the time to take the mid all apart you might as well spend a few hours correcting core shift and get rid of the casting (&%&**(()% in the runners .

https://i.imgur.com/gchjKBfl.jpg

https://i.imgur.com/206Xw4Bl.jpg

https://i.imgur.com/TimcXY1l.jpg

[One Oldman]

"Just" cutting the inner liner will give the exhaust a larger area to expand in before it meets the same "total exit area". There is room on the bottom of the cavitation plate behind the back set of 12mm studs to drill a few .625" holes .
It will be quiet @ idle and move enough air at WOT to be happy .

The tuner leave's a bit to be desired . But if your going to take the time to take the mid all apart you might as well spend a few hours correcting core shift and get rid of the casting (&%&**(()% in the runners .

Do you have any pictures of the .625 hole locations? Thanks

[Varmint]

My bad , I thought you made a statement . Theorized from the compilation of your readings ... :smiletest:

"Just" cutting the inner liner will give the exhaust a larger area to expand in before it meets the same "total exit area". There is room on the bottom of the cavitation plate behind the back set of 12mm studs to drill a few .625" holes .
It will be quiet @ idle and move enough air at WOT to be happy .

The tuner leave's a bit to be desired . But if your going to take the time to take the mid all apart you might as well spend a few hours correcting core shift and get rid of the casting (&%&**(()% in the runners .

https://i.imgur.com/gchjKBfl.jpg

https://i.imgur.com/206Xw4Bl.jpg

https://i.imgur.com/TimcXY1l.jpgthats real nice work, tks. For the reply and info

[Varmint]

I had to take it apart to cut 5" from the water tube and degrease and paint it, had some salt use at some point, i see where you mean to drill holes in can

[One Oldman]

I had to take it apart to cut 5" from the water tube and degrease and paint it, had some salt use at some point, i see where you mean to drill holes in can
Dang you have an advantage on me...You have yours apart.:eek: