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Matt here is the extra gear case you need
http://www.kijiji.ca/v-boat-parts-trail ... 1276707727

sssshhh! Don, a little more on the down low, maybe..

thanks!

did you see this one? looks minty from the outside.

http://www.kijiji.ca/v-powerboat-motorb ... 1268874926

YEP, I saw that one. Too costly to think about. I will be mad at myself if that Mariner is a 6F0 model with the exhaust pipe and separate muffler.

it is not a 6F0

Don,
I grabbed that motor the other day. It has melted pistons. I checked the lower before buying it and it looked good.

So I brought it home, opened the water pump and the impeller has basically completely eaten up. I happen to have a new impeller at home already, so installed it, new pump gasket, new gear oil, and took it for a test drive today. Turns out it has 1.71 gears!

Boat did not behave at all like at Gravenhurst. Just to confirm the suspicion, I marked the flywheel and prop and it takes just less than 1 3/4 turns of the flywheel to get the prop around exactly once.

Here's what's quite odd though: I marked the driveshaft and propshaft on my other gearbox (the one I used at Gravenhurst). It is coming in at almost exactly 2:1.
I swear the gears that went in were 13:24. Pinion is definitely 13. Just double checked again. Exactly 2:1 when watching the marked shafts..

edit/update: I found a photo of reverse gear from my original gearbox: 26 teeth. Also found a pic of forward gear: 26 teeth, stamped "679" on the back. Searched "679" and looks like that gear is from an old 40: "1977-1979 40B", and the 2Cyl commercial 40.


M

How was the boat with the different gears? Did it make a difference other than pull the rpm down or did it even do that?

When going out to test the new lower, I never considered the gears might be different.
I went in to this test session with this idea: run the exact same setup as Gravenhurst but with the smaller of my two props (the weirdo one I showed people) to see how high of an RPM I'd see.. That was basically the only change, but with some added weight.

Well the boat did not get on plane so easily, and then watching the speedo and tach at mid-range I was wondering how this setup could get me these speeds... It was at that point I figured it could have 1.71 vs. the 1.85 that I thought I had in the other lower, but man the difference was significant.

So in the end it made sense to discover my original lower is 2:1. Makes my prop slip numbers look better, but the boat/motor combo look less powerful than I had thought.

BTW, I just checked plugs and piston wash: excessive wash, and plugs are dark brown like Guinness. I'm hoping I can find more power out of that motor somehow.

I only saw 52.5 with the wind (gusty, windy day) with my smaller weirdo prop (11.25x18) and this new lower. Same motor height as Sunday at Gravenhurst, carrying more fuel.. I'm sure I saw more than that with the larger 12x19 prop and 2:1 lower at Gravenhurst on Sunday. GPS has a 54mph segment recorded from that race.

Matt , try running it with the prop you raced and see the speed and rpm?

I would like to. I didn't that day because it had a hard time getting on plane with the smaller prop. I suspect I'll have a hard time getting on plane (see above description with small prop). RPMs will be lower due to higher gears. Kinda wish this 12x19 prop was vented.

The smaller less efficient prop had minor trouble getting the boat on plane with the 1.71 gear lower. But I could easily lose 40 or 50 lbs (seat and smaller gas tank).

I'm going to try my best to have a T750 motor on this boat for the next race. Although this 70hp was slower than T750 boats, not sure how I'll do with a smaller motor.. Either the boat is heavy and hooked, or the 70hp is weak, or all of the above..

M


I have two props, both are Ron Hill Signature semi-cleaver thru-hub. One is 12x19 (diam is actually larger than 12), the other is 11.25x18 (diam is now smaller than 11.25). the 11.25x18 was "sharpened" and balanced by Kawartha. They did not thin the blades at all. It also has "cup" on the leading edge (weird, and not sure that is helping at all). And according to prop slip calcs, the weirdo 11.25x18 is not as efficient as the 12x19. Now that I know the actual gear ratios, I'm getting 11% slip for the 11.25x18" and 7% slip (Gravenhurst race) with the 12x19".

Matt..the prop slip i am assuming is why its hard to get on plane? I assume the prop was blowing out trying to get on plane or was it the fact the motor bogged down?