height-angle

[johnsonm50]

A question about tunnel hull propshaft height and angle, Ive got an A or B size tunnel to put an AB merc type motor on and dont know whether to go by the tunnel or sponson bottom line or whether to be in or out on angle. I want to generally start conservative but be close enough to not change the transome height. Thanks, Mike

[bh/]

tunnel

Not sure if u are sayng u have a A-B tunnel hull, or a A-B hydro with a tunnel. In any event set the motor height relative to the riding surfaces at the aft end of the boat, not the tunnel. The height will depend more on prop design than anything else, but a conservative set up for a modern three blade would be to bury the prop shaft 1 & 1/2" deep, but keep the cav plate at least an inch above the water surface, and set the angle parallel to the riding surface at the aft end of the bottom. Clear as mud..???
This should get u up on plane, and then go from there.

[johnsonm50]

Thanks Brian, Its a full tunnel hull similar to what used to be raced. The riding surface it is.

[STEVE FRENCH]

I have a Glen-L Tunnel-Mite (sit-down) that we run a 1958 35HP Evinrude on.....going To set-up a 30H powerhead on a "Q" tower with a 102 Yamato foot this Spring....Exspect to start below the bottom of sponsons 1-2" deep also have a 25SS to try, and would start the same with it.

Will stop and check current height on the Rude and take a couple pics......I know when we went much higher it would start to "blow-out" gitt'n on plane...... We Ski and pull a tube with the Rude!!

Keep us posted and take some pics!

19P

[johnsonm50]

Thats really cool Steve. This being my first tunnel I wasnt sure on that. I have several choices of motor inc. recreational & race type. [one is a 79 OMC 25 with a 102 14:15 foot]. This is a 10ft 6in sit down or kneel boat from leftover wood of another build. Its been a long time due to bouts of messin with other stuff but its getting close now that I need the space its in. Mike