12ft Tunnel Build

[John Schubert T*A*R*T]

Ron.
Very interesting concept never knew that till now.
.
Not quite the same but this helped - when I was using 1:1 gears in the 20H with 2 blade props (circa 1970's) I would try different spline engagements of the drive shaft into the power head to change the diving blade position of the 2 blade prop relative to the piston position on the power stroke. This put the best position of the diving thrusting blade into the water/air mix and the other lifting blade out into more air less water, like slapping the water at the right position with one blade. There were noticeable improvements. Didn't work as good with 16:21 and/or 3 blades but did help some. Every little bit helped to win, even if just 50 rpm more.
Pete

My father always put the prop on & placed it in a position just passing the gear case. Then he would put number 1 cylinder at TDC & mount the powerhead whether 2 or 4 cylinder motors

[zul8tr]

My father always put the prop on & placed it in a position just passing the gear case. Then he would put number 1 cylinder at TDC & mount the powerhead whether 2 or 4 cylinder motors

John
Interesting at least that was a consistent process, that is important. I just tried several spline positions for the best one with the 2 blade props at the time. I found it easier to remove the gear case, set the top piston where wanted and put the gear case back with the prop near desired position. I found that with 1:1 gears and the 2 bladed props set about horizontal and piston about or a bit after TDC was about the best for my rig (positions limited with # of splines). Didn't matter that much with 16:21 gears on two cylinder jobs with 2 blades due to changing cyclical blade positions each blade rotation that repeats each 16 blade revs. Never raced the 4 cyl engines so no experimenting.
Pete

[ice_spy]

Ron, i had the boat out today. My water leaking inside the motor problem has been side cover gasket. It let go from not re torquing it up again consistently.
So today i ran the new Clever u sent me... wow.. this prop is so amazing it scares me. It really lifts the whole boat out of the water and increasing postive trim sends it towards 7k, but the boat is so hairy with postive trim and speeds over 65mph i have not yet reached max speed from this prop yet. i stopped at 6900rpm and 66.2mph. Unreal prop for glassy days as it was today. hole shot is awesome, and it corners the most predictable from any prop ive used yet. Thanks again Ron, this prop really gets the adrenalin running and is exactly what i was after. fast, and has more it in then i want to try in my little 12.5 tunnel boat. lol.

[Infoless Racer]

Ron, i had the boat out today. My water leaking inside the motor problem has been side cover gasket. It let go from not re torquing it up again consistently.
So today i ran the new Clever u sent me... wow.. this prop is so amazing it scares me. It really lifts the whole boat out of the water and increasing postive trim sends it towards 7k, but the boat is so hairy with postive trim and speeds over 65mph i have not yet reached max speed from this prop yet. i stopped at 6900rpm and 66.2mph. Unreal prop for glassy days as it was today. hole shot is awesome, and it corners the most predictable from any prop ive used yet. Thanks again Ron, this prop really gets the adrenalin running and is exactly what i was after. fast, and has more it in then i want to try in my little 12.5 tunnel boat. lol.

Hi I have been reading this thread religiously. Just wondering why are some of the pictures not showing up on the posting?

[ice_spy]

Its been a long time since my last post. My apologies for the disappointment in the pictures not showing up.
A while ago, Photo bucket threatened me with deletion of all my stored photos unless I started paying, for what was once a free host site. The only option was to delete photos to reduce my stored amount, in hope that I could save some. Before I knew it, almost all of my build photos were deleted from photo bucket, destroying my image links to their site. The photos can be seen on Dillon Racing Plans website. I will have to go through the process one day to restore them.
Recently I have just swaped motors from the M50D to the M40C, to be in a legal AustralianPBA super sports 550cc class. I hope to show my fellow Aussies, in their V hull wing boats what a great boat the Dillon Racing tunnel hulls truly are. Acceleration is going to be my concern to keep up, as they the 25 / 30hp mercury / tohatsu engines that are lighter than the M40C and are quick revving.
I have a spare powerhead, where the rules here in Australia allow any modifications to the engine so long as it remains under 550cc. So some porting and mods will follow soon. Does anyone have any power secrets they wish to disclose for the M40C ?

[ice_spy]

[ice_spy]

[ice_spy]

Some more pictures of the modified Sport C Dillion Racing Plans, 12ft tunnel with the M50D on heat

i was feeding her some positive trim for Quinno the camera man here the boat is extremely predictable and now I've put a few hours in on the water, I know how to control it alot better now, especially around the turning boys, it corners very very well, in fact with Bob's (Chairman) advice, I may need to take the sharp 90° off the inside of the sponsons a couple of feet from the bow to stop it biting in so hard. I am yet to do this.

This picture is at the River race with return leg, named the Double Dash. This is the new Bridge to Bridge race that unfortunately has now been cancelled. My dream to race this boat in that race, may never be realised, however the shorter Double Dash on the same river showed me what endurance would have been needed for such a long river race. You can view the race here on YouTube:-
https://youtu.be/-X0jVl2XHiw
You can see me @ 3:40 & 4:40.

Presently shaping up the gearbox for LWP for the M40C swap.

[ice_spy]

That looks better. In primer for now, should have it finished soon.

[ice_spy]

turned out OK for now. Over sanding, will fine sand it smoother next time it needs a coat of paint.