Question for 3.0 Gurus

**One Oldman** · 02-13-2018, 03:22 PM

2003 XB 250. I need to vent the exhaust above the prop. What is the best, easiest, and cheapest way to do this? I'm not concerned about noise and I'm not looking to gain or lose any power. Could you not just cut the bottom out or remove the exhaust tube and drill holes at the cavitation plate, like the 2.4s were done? THANKS

**vnemous** · 02-13-2018, 03:59 PM

Pull power head, remove exhaust plate and cut the tuner off at first parting line up from the bottom.

**One Oldman** · 02-13-2018, 05:02 PM

No need to drill the mid? I'm sorry I don't have one off in front of me.

**vnemous** · 02-13-2018, 07:24 PM

Reach up above your cav plate you will find it open into the can. The noise will come out there. Check this video you will see what I mean where the water and exhaust comes out right above my sportmaster.

https://youtu.be/UNvZk8Xu8gc

**vnemous** · 02-13-2018, 07:28 PM

Here is where you cut the tuner. Pic supplied by Simon Motorsports

Attachment 399638

**One Oldman** · 02-13-2018, 08:28 PM

Well, the attachment link doesn't work. Drats! Anyway what I plan on running this on is a shadow vt hull and everything I've read says that the hull works best with a chopper or chopper type prop. I will be running the standard gear case but will have it coned. I have heard the standard case will not be happy with OTH props due to over ventilation which is the reason I'm asking about this. Do you have any knowledge concerning running these heavier 3.0s on STV type hulls. I don't know what mine will weigh yet but it's been on a diet and I'm hoping for something around a stv euro weight

**vnemous** · 02-13-2018, 09:47 PM

Click image for larger version.

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**vnemous** · 02-13-2018, 09:49 PM

We have had quite a few customers and friends running 3.0 with cut tuners on STV and over hub props. In fact its a very common setup.

**One Oldman** · 02-13-2018, 11:39 PM

Great info thanks.

**Varmint** · 02-14-2018, 08:48 AM

I ran mid 90's steady on those hulls with just a 2.4 bridgeport,,mine loved a mazco re4 or a worked srx27/29,,, honestly I dont think my 250 pro xb with 300pm mid and alien weighs more than 50lbs more than a 2.5. factory specs say the 300 pm was 445lbs.

Originally Posted by One Oldman

Well, the attachment link doesn't work. Drats! Anyway what I plan on running this on is a shadow vt hull and everything I've read says that the hull works best with a chopper or chopper type prop. I will be running the standard gear case but will have it coned. I have heard the standard case will not be happy with OTH props due to over ventilation which is the reason I'm asking about this. Do you have any knowledge concerning running these heavier 3.0s on STV type hulls. I don't know what mine will weigh yet but it's been on a diet and I'm hoping for something around a stv euro weight

**Varmint** · 02-14-2018, 08:53 AM

I recently weighed a 300 pmax mid and cowling for shipping on a certified scale,it was 225lbs. so add 70lbs. l/u,and the weight of the powerhead, not sure what the powerhead weighs exactly,I have a dressed 250xb on my shop floor,I should go weigh it someday,before I mount it up on a mid.

**One Oldman** · 02-14-2018, 09:59 PM

Thank you so much for joining in 'Varmint'. I knew there was someone on one these boards that had ran big numbers with these old hulls. Most everyone I've seen run big #'s were running over hub props and 12" jack plates. I'm wondering with the extra 50# of weight if I should start with a 10". I actually have both though I would need to make sure the 12" is rated for the weight and HP, SlideMaster.. It looks like it's made of mostly .425" stock. The 10" I have is a heavy (in more ways than one) CMC and the stock is over .500". The true weights on any of these motors appears to be some kind of trade secret.LOL It's hard to find two places that list the weight as the same for the same thing. So for the sake of arguement, I'm going with the Mother Merc service manual weights.Again, thanks for your comments.

**Varmint** · 02-15-2018, 05:00 AM

I ran a 12" rapid jack,before steve bought them out,,great plates,but a 2.4 bport is a lot lighter,than a 250xb,I think the cowling on a 250xb weighs more than a BPort,

, to me the 250xb needs to shave some weight in the cowl dept. Alot of days,I still wished I never sold my shadows,and they are so easy to drive. Like any performance boat,you just gotta' balance them well. I dont think you will have any issues with a 250xb on 'em,,plenty of them had the heavy old omc 235's back in the day. everybody said you can't put a 3L on your ally xb03,,damn,it's all I see on 'em these days. I had a brand new 250 pro xs last year,and everybody was negative,,wish I woulda' tried it,,,

,oh well, I just got a l/u for my xb,so will try it this summer.

**Varmint** · 02-15-2018, 05:03 AM

You may wanna add a couple knees to the transom,kinda easy to do on a shadow,the years varied on their quality of build. originals had Mohogany ply.,transoms.

**One Oldman** · 02-15-2018, 02:30 PM

I have seen some old posts where pretty good #s were put up with old 225/235 OMCs. Mine is not a Cox built boat. It was made by some 'fly by night' outfit that appears to have been in business less than a year. From the serial # it looks like mine was the 3rd one built. It has a foam transom but beyond that was very poorly built. I removed about 75% of the layup and went back with a 3 layer that was about 1/2 as thick as original. There is 0 wood or foam in the hull now. I reduced the height of the knees by 3-4" at the notched area and extended them into full length stringers. Added knees on outside of sponsons incorporated into full length stringers. Incorporated 3 small knees in V pad into full length stringers. Used all epoxy and 3/4 honeycomb laminate board. Less than 39#s per sheet. Input is welcomed