I understand what your saying. I wasn't comparing diesel boats I was shooting for gas powered boats which I didn't make clear.

On the Nortech that does 83 what's the gearing?

I didn't ask about fuel rate to calculate to actual HP. If they haven't done it yet, they will.

Since its full-authority electronics, and the statement was made that it was running ~70 at rated speed (3400 rpm), this only suggests that they're not over propped with the 17x37.

If the governor begins to pull fuel right at 3400, allowing only 50 rpm of no-load overshoot, they could be under propped. I thought I heard that they tried the 17x39 first, so this would be a counter-point to my previous statement. If they couldn't pull the 39 to rated speed, I'd say they're pretty close to using everything the engine has in it.

This isn't to say that the efficiency of that particular combination is as good as it can be. That type of change seems like something that gets you 1-2 mph.

Purely from a top speed perspective, which is more efficient...bigger wheel, reduced pitch, same rpm or smaller wheel, reduced pitch, higher rpm?

There are an many ways to put 480hp into the water, and each has tradeoffs. I'm not so sure they haven't hit one of the better ones right out of the gate.

he is running a 1.18:1 ratio. I should also say that we really only play with the larger diameter stuff on the LY engines and arnesons. We don't do many arneson boats with the smaller LP engines.

what are you guys thoughts on multi speed trannies??

obrein,

So you validated what I keep saying which is "you need prop speed to go faster" not pitch or dia.

Your running the 1.18, just look some real loose logical deduction here.

1.3's put you in the 70's
1.15's put you in the 80's
.8's I know from the EBEL put you in the high 90's
.6's I know from Gancia put you in the mid 110's

You see the pattern .2 taller gearing gives you about 20mph in every case. I know this is loose but the pattern and the actual applications prove it to be a logical deduction.

There are many problems with tall gears so when stainless asks "what are you guys thoughts on multi speed trannies??".

That is how you overcome the pitfalls of tall gears. I wrote alot on here about our projects with Twin Disc and the yellow Don Shead boat from the UK with #3 drives and it's hydraulic "slipper" overdrive trans.

Stainless, the theory behind them is 100% sound - I have never had the luxury of using them as they did not exist in the form they are today. We ended our work almost 20 years ago.

Joe Gere

Thanks joe. The new cms boat is using some close ratio 4 speed units. It might be cool to try something along those lines with a diesel app.

habanajoe,

I agree completely on needing prop speed. However we have had luck on several boats running more diameter that gave us higher efficiency. The 50' we have been running has a 1.5 ratio and runs 67+ in the 3450-3500 range which is all we can turn rpm wise.

I quess what I have should have said earlier, is that they definitely need more ratio to run the size props they are trying right now (i.e. more prop speed). with the ratio they are running I was only suggesting that they try a bit more diameter rather than continually adding more pitch.

obrein,

I agree with you, I can tell your a smart guy.

I like to debate things and see what comes out of it.

I think we're all on the same page here, everyone wants to see this boat do great.

On a whole another note didn't Weisman make multi-speeds for a couple Seatek race boats? That might be what this boat needs a 2 or 3 speed with OD to raise the 1.32 up toward direct?

I know a little late in the game now, but after the last two days I'm not getting any new boat for awhile so I have to live through everyone else for now!!!!

Joe Gere

I don't know how many Class1 diesel boats had Weismanns, but they were very popular. Zero Defect(Laith Pharaon/John Tomlinson) had Weismann 3 speed trannies and drop boxes when they went undefeated in 1996 I believe. They were banned at the drivers' meeting after Key West.

Good stuff guys... Much appreciated...