Transom mounted water pickup

[Mr. Demeanor]

First off, hello and all that. First post here but no stranger to the boating forums.
I do not have a hydroplane but I do have a pretty fast little tunnel hull boat. It is a 13' Biel full tunnel with a 130hp Yamaha. I presently have a Bobs nosecone/lwp but I am losing water pressure and just tired of re-epoxying the lower unit.
I have decided to try a transom mounted low water pickup. I have searched around the net and presently have a thread going over at www.screamandfly.com but there not much info out there. I was thinking that you guys probably run these and may have some thoughts.
I just finished mounting a Bobs Machine adjustable pickup. If the wind allows, I will make some passes this weekend with the pickup not plumbed but just want to see how it effects speed and handling before proceeding.
My initial thought was to reduce drag I would mount the pickup a little high and grind a small "ramp" into the trailing edge of the hull just in front of the pickup to feed it water. I modified the mount to hold the pickup tube flush against the transom.
I plan to plum the pickup straight to the existing fitting for the bobs nosecone at the water pump cavity.
I know there will be some trail and error with height but any advice on how to adjust this pick, modify its shape, etc. are appreciated. Pics of your setup would be great.
My goal is 85mph and I have run 82.6mph so far. I think a little more engine height will get me there.

Heres the existing thread at S&F:
http://www.screamandfly.com/showthre...t-water-pickup

A couple videos of the boat. Took one video using a waterproof camera of the lower unit losing water pressure that came out real nice. I had raised it another 1/4" for this run and lost pressure at 78mph.


http://www.youtube.com/watch?v=yMF31PI111s

http://www.youtube.com/watch?v=Br6JV..._order&list=UL

[STEVE FRENCH]

Mr.D,
Just be carefull!!!!.....You are near'n a point of "break'n-loose"...or walk'n on the prop

Happens with a hydro when you get the engine set too high in da pursuit of speed.

With a tunnel you are already high because of the tunnel funnel'n air to the foot......

Would be very scary to see ya break loose at 84.9 MPH!!!

I have play'd with speedo/water tubes to feed my Yamato MOD motors......The yamato foot has no water pump and relies on the prop to feed water to hole and passage thru tower to powerhead.....looks like the water pick-up your work'n with will fill a garden hose!!....should feed plenty of water once you have it set......I have a 10ft Glen-L tunnel Mite with a Yamato with same issues.....Just watch if your rig starts ta git loose....especially just as you start to back-off throttle and nose dips and back gits squirly......your near da point of NO-RETURN!

PS....Keep the nose cone.....We also have a 135MERC with stock blunt foot on a 13 ft tunnel.....handles like crap......wait'n to add a nose like on yer foot.....

PSS....You might even add a "T" to your speedo pick-up, run a 3/16"-1/4" line to feed powerhead and be able to maintain the water your now lose'n.....take GPS with ya to compare speed in case it affects your speedo?......(or eliminate/bypass the speedo?)

[Bill Huson]

easy answer . . .

Jet it rich (more fuel) and feed the engine Giggle Gas = nitrous oxide.

[Mr. Demeanor]

Thanks for the comments Steve. I actually considered t-ing the speedo pickup into the new water pickup and eliminating the speedo pickup.

[Mark Monkres]

STEVE FRENCH!

I still have the original popular mechanichs magazine that showed the Tunnel Mite off of San Franscico Bay I drooled for years. How Does it it run? Couldn't cut enough grass to buy the kit when Glen-L would send you pre-cut pieces.

O-49 Monk

[sam]

also have a 135MERC with stock blunt foot on a 13 ft tunnel.....handles like crap......

Frenchie, not many 13 ft boats have enough butt for a 135 Merc ... can you post a picture ... my first impression would be that you are just putting too much motor on the boat ... (says the owner of a 14.5 ft E&T with a 135 ... duh)

You got something bad in your setup if are having problems with a 135 Merc on a tunnel and a nosecone is NOT going to help. Consider all your setup options including the prop ... no one makes or made a nosecone for them, because they don't need them ... 150 Mercs ran over 100 mph in SJ and not far off in FJ ... without nosecones

[dcrummett]

Monkres, you'd have killed yourself if you'd gotten all that grass cut and turned it into a tunnel mite! But weren't those the days of looking at the Glen-L catalog... hmmm not much different today!!! ZIP, TNT, SQUIRT... all of 'em look like fun... as long as they are overpowered!

Dan
O-66

[johnsonm50]

Home made answer on a smaller scale>>

This is about 3/8ID but could easily be upsized. By ramping up to the pickup I doubt will avoid much drag because the pitot still has to drag to work, the ramp may even cause more.
Cool rig! The codes are 'off' so Ill try the pic again later or maybe you can get it from here. Good Luck

[Mr. Demeanor]

I ran into a little setback (no pun intended)
I took the boat out and made a couple runs but it was too windy to get a good stable top end run. I decided to go ahead and put the pickup tube in the bracket and beached the boat. When I went to stick the pickup in the bracket, I found that the back of my sponsons were actually sitting in the sand. The boat sits so bow high at rest with nobody in the drivers seat that the sponsons sit in the sand on a gradual sloping beach. This could be a deal killer.
I am also going to look at moving the pickup holes in my existing low water pickup/nosecone further back. My eyeball guestimate is that I can pick up about 1/4" more depth. I I remove the nosecone and do some fabricating I may be able to get more.