Allison SS-2000 Excel

[aeneas]

Well, we'll see what happens...

[SANTAFE]

OK easy and not lots of money. find a 260 power head with maybe just rod slots done or not. Put a set of 21cc heads on it and then watch it go.

[whipper]

Looking good Aeneas ! Sick setup. More trim and Even or 1/4 to 1/2 inch bellow is what alot of guys like Jay Leach, Roy Roach and Sam Baker have said they run there SS. Those 3 are very very long term runners of these hulls and fastttt. Above the pad you cant run the correct slight 2 or 3 deg positive trim to have the prop shaft aligned for maximum thrust and hull angle of attach to take advantage of the aerodynamics and hydrodynamics built into the hull and pad i would say? With lower rpm motors you need the hull to work with you. Running a SS with a 200 into the high 90,s more difficult than running an SS with a 260 to 105 for instance. to run 97 mph with a 30 your to the floor with max trim settings. With a 260 or 280 at 105 your to the floor with still a few bumps to go!!! LOL

[aeneas]

whipper, I think there is a mph or two still in there...
The reason for jacking the engine so high is that as you pointed out I do not have the most powerful or high revving of engines and I want to get the least possible drag from the lower unit yet still let it carry some weight. With this setup I can run virtually neutral on the trim and the boat lifts anyway. In the pic you see very little of a rooster indicating quite an efficient setup. The SS2000 is such an efficient hull it runs best with a low/small rooster according to the guys at the Allison forum.

I just ordered a drum (200 liters) of Apen+ Alkylate fuel (@ $11.75/gallon).

See the chart above. It is a test to see how the engine runs with that fuel. I called Mercury Racing and they said go ahead, also in Sweden this fuel is mandatory in certain Offshore racing classes. I used to run it before but stopped since my gas station stopped selling it.

[whipper]

i hear ya. if you still have a 100 or 200 rpm left sitting there that fuel should get you that with the big wheel. in that last clip at 55 sec did you see that big fish jump right beside ya!! LOL Looks good im sure youll get her were ya want her. i love your setup such a sweet ride!!

[MStine06]

I ran my SS with a 280 1/8" below to even with the pad. Never had a need to go higher than that. The boat would handle very well and would easily run the numbers it should.

[aeneas]

MStine06: I am 1mm above even with the pad, so about your setup. The boat handles like on a string - no chinewalks - just straight and I hardly need to correct with the steering wheel.

[whipper]

Bellow the pad the gear case angle is slightly positive. 2 to 3 deg. this allows water pressure and a level motor but the hull to have the bow a little higher and less stern area in the water, more only on the pad allowing the lip and pad to work properly along with the {wings} to carry the hull with less effort. The air moving over the bow enters the exaggerated hollows in between the strakes trapping air to create a pressure differential to aid in the over all lightness the prop has to provide thrust for. The fastest gear case position will be half in half out. The bullet then deflects the water away from the sides of the case and ideally the spray re-adheres just before the blow out ring so the prop has enough water to grab and create thrust. To reduce down force at speed from the upper deck the hulls attitude plays an important role. Most will find bellow the pad to be the optimum setting for all these areo dynamic and hydrodynamic factors to align. For kicks and giggles years ago I made a mickey mouse wind tunnel using a roll of streamer tape and big arse fan in my garage with the door on the one side open and rolled the hull in facing the back of the garage so the air went out the doors. I adjusted the bow with the trailer jack on a block and found for down pressure, if the bow wasn't high enough the down force went right into the back seat area acted like a parachute!! It didn't take much to change were the streamers went up or down. The SS has a Narrower rear seating area in the cock pit that would act better for less down force than the GS buy far. The best design for speed on the upper deck is the XR2002 and XR 2001 as we all know. The rear seats in the XR 2002 design flow the air out of the cockpit better to create less down force reducing over all drag in both the air and water. Hence why boats that have a big flat bench with lots of power are faster with a race hatch on even though that adds weight. The over all drag is reduced.

I only said all these things because most guys think of speed equated to power, prop and prop shaft height. With hulls like ours theirs alot more incorporated into the design and when approached with all these factors in mind you will be able to optimise your setup further. Plus much safer knowing why things do what they do. Any 20ft boat capable of 100 mph with a 200hp motor had alot of thought into the design. If you ever get a chance to pick Darris brain have a pen and paper ready because he will blow your mind. HaHa

BTW Less gear case drag is achieved buy blunting the bullet. Just have to watch on the bottom of the bullet so your not deflecting water away from the pickups. For Allison speeds 110 or less round like the end of your finger. If theirs any blowout then you just have to make it a little smaller. You can pick up 1 or 2mph this way. Allison cut Swept skeg also works good. The higher the pad is to the surface the faster you will be with less rpm. i know you know all this but its sometimes good to have a reminder pluss i was board.

[whipper]

Not just for show.