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7.5 OB Lower unit for tuned pipe

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7.5 OB Lower unit for tuned pipe

Old 02-18-2006, 11:54 PM
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Default 7.5 OB Lower unit for tuned pipe

I am looking for a new or used 7.5 K & B milled lower unit for placing a wrap around style tuned pipe which I also am looking for a new or used pipe as well.
I have peaked on performance and won ribbons with my Stock 7.5 and it is time to step it up a bit I think.

I will be placing this on a new tunnel hull I am designing.

Links, Tips and Parts offers welcome.

Thanks, Jeff
Old 02-19-2006, 07:20 AM
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Ron Olson
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Default RE: 7.5 OB Lower unit for tuned pipe

Ever think of modding your stock one? It's pretty easy to do. If I can do it, .....................
Old 02-19-2006, 11:42 AM
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Default RE: 7.5 OB Lower unit for tuned pipe

I used what I had handy. I first drilled a hole at least 1-1/4" using a hole saw for the radius above the cavitation plate then did the major cuts with a hacksaw. I smoothed off everything with a mill file. The water pick-up I modified by flipping it around and holding it in place with some of those nylon throttle cable clamps bolted though the cav plate with countersunk screws. Some people will leave part of the old exhaust system in place to use the water pick-up as-is.
Look over everything before making any cuts as you might want to do things differently. If I were going to go another route, I'd use a lower from Lawless/R Manufacturing that is made for tuned pipes.
Tuned pipes. I haven't had to shop for one of those for an OB tunnel in a while. Maybe Mark or one of the other OBer's can point you in some directions.
Old 02-19-2006, 11:45 AM
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Default RE: 7.5 OB Lower unit for tuned pipe

Ron, Good point, what did you use to cut it and where can I locate a tuned pipe that bolts to the engine?? If I trash this one, I can buy a lower unit just as easy as buying a modded one for more money

Jeff
Old 02-19-2006, 11:54 AM
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Default RE: 7.5 OB Lower unit for tuned pipe

Thanks Ron, I was thinking of my bench grinder but aluminum is horrid on a bench grinder as you probably know, Drill it, hack it and file it sounds good to me!!

Found this company "http://www.precision-boats.com/" they have pipes and headers. looks like a $100.00 conversion.
Anybody know of other companies..

And any clear Pics of your lower end 7.5 units that have been cut for a tuned pipe would be great. Just for some visual direction.

Thanks, Jeff
Old 02-19-2006, 12:02 PM
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Default RE: 7.5 OB Lower unit for tuned pipe

I might have some in my favorites under my other screen name, I'll have to look in there. I don't use that one hardly at all but I have to keep it because it's my master account name.
Try 707 Specialties. The do have a link in the NAMBA website to make it easier to find. I'll check my other OB manufacturer links to see what they have.
Old 02-20-2006, 11:35 PM
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Default RE: 7.5 OB Lower unit for tuned pipe

Tim and Josh at PBR are great people to deal with. I get items from them all the time.

Stock:


Ready for pipe:



707 Spec. is also good to deal with. Might want to check with Props-4-U as Mark is a U.S. dealer of SPP carbon fiber pipes.
Old 02-20-2006, 11:38 PM
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Default RE: 7.5 OB Lower unit for tuned pipe

BTW: the above lower was cut via a metal band saw and cleaned up with a mill. Took all of 20 mins to perform.
Old 02-21-2006, 08:04 PM
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Default RE: 7.5 OB Lower unit for tuned pipe

Thanks for the response Mark, I will get going on cutting as soon as I get the pipe and header.

Jeff

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