Yamaha HPDI gearcase mod..

wildcatt · **Joined:** April 29th, 2012, 7:26 pm **Posts:** 503

allstock wrote:

Alright now that I'm there I'm going to do the four holes, it's on the bench with the tools out so why eff around. I'm going to leave the half-shut screens the way they are and try it. I can pull them off and epoxy them shut easily if need be.

Have you tried it in the pond yet Mike?

allstock · **Joined:** August 30th, 2012, 11:21 am **Posts:** 325

wildcatt wrote:

allstock wrote:

Alright now that I'm there I'm going to do the four holes, it's on the bench with the tools out so why eff around. I'm going to leave the half-shut screens the way they are and try it. I can pull them off and epoxy them shut easily if need be.

Have you tried it in the pond yet Mike?

Yes I ran it quite a bit yesterday, I'm totally happy with the results! I can jack it until the prop loses bite and still maintain 15psi at WFO. It doesn't seem to ever go over 25psi, which is fine but I never drive it with the shaft much more than an inch under. At top end I think I'm about 1.5" above, maybe more I'll measure it out of the water.

DoktorC · **Posted:** June 8th, 2014, 10:49 am

That's very interesting. How much height did you gain over the stock inlets? I may take off my closed and try a set of stockers. Mine are trying to blow out of the gearcase.

allstock · **Joined:** August 30th, 2012, 11:21 am **Posts:** 325

DoktorC wrote:

That's very interesting. How much height did you gain over the stock inlets? I may take off my closed and try a set of stockers. Mine are trying to blow out of the gearcase.

I never ran it at all with stock inlets, I epoxied the top half shut before I put the lower on. I would say I gained an easy 1". If you've got too much psi I would try a stock set with only the top half shut, it seems to work for me at the moment.

DoktorC · **Posted:** June 8th, 2014, 7:03 pm

I honestly thought it would blow the water right out the screens give how the water enters from the lwp. Learn something new everyday..

allstock · **Joined:** August 30th, 2012, 11:21 am **Posts:** 325

I'll put the go pro On it next weekend, maybe we will be able to see what's going on. I only ran my 26" this weekend and it ran the exact same speed as before... I'll try my 27" next weekend and see what happens. I may not have gained any speed BUT the water psi is way more stable now. It use to drop off if I turned sharp or had the motor trimmed all the way in, but not now.

wildcatt · **Joined:** April 29th, 2012, 7:26 pm **Posts:** 503

allstock wrote:

I'll put the go pro On it next weekend, maybe we will be able to see what's going on. I only ran my 26" this weekend and it ran the exact same speed as before... I'll try my 27" next weekend and see what happens. I may not have gained any speed BUT the water psi is way more stable now. It use to drop off if I turned sharp or had the motor trimmed all the way in, but not now.

Good stuff Mike. I'd like to see that vid. When it's ready.

allstock · **Joined:** August 30th, 2012, 11:21 am **Posts:** 325

http://s1222.photobucket.com/user/kusho ... 2.mp4.html
Alright I kinda struggle with uploading shit but I this should work. No wonder I was running out of water pressure. Don't mind the huge rogue wakeboard boat waves I hit... I have a vid of a full blowout on the top end, I'll try to post it up. Btw psi never dropped below 15 on this vid.

allstock · **Joined:** August 30th, 2012, 11:21 am **Posts:** 325

http://s1222.photobucket.com/user/kusho ... 8.mp4.html
This is a good one. It looks pretty tame on the vid but I thought was going around in a circle at 80mph!

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Yamaha HPDI gearcase mod..

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