Ox66 case vs HPDI

DoktorC · **Posted:** August 18th, 2013, 8:19 pm

allstock wrote:

Did some preliminary testing today with an HPDI lower. It had five exhaust relief holes in each side, and slightly modified water intakes. I found the results interesting.
Pros of HPDI unit...

4) Overall seems to be a tougher unit, the bearing carrier is retained better IMO.

The HPDI lower is designed to be run closer to the surface (obviously) so it is beefier AND uses better prop shaft and shift shaft seals. We (Sr.) upgrade all the OX cases to the HPDI seals whenever possible.

Great testing btw...very interesting differences between the two cases.

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

BoomerMuskoka wrote:

how much did your rpm change with the new ratio ?

5800 vs 6000. I could go down an inch in pitch and I think it would work better all around.

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

DoktorC wrote:

allstock wrote:

Did some preliminary testing today with an HPDI lower. It had five exhaust relief holes in each side, and slightly modified water intakes. I found the results interesting.
Pros of HPDI unit...

4) Overall seems to be a tougher unit, the bearing carrier is retained better IMO.

The HPDI lower is designed to be run closer to the surface (obviously) so it is beefier AND uses better prop shaft and shift shaft seals. We (Sr.) upgrade all the OX cases to the HPDI seals whenever possible.

Great testing btw...very interesting differences between the two cases.

The hpdi unit "appeared" to have Viton propshaft seals, are the two seals the same dimensionally?

DoktorC · **Posted:** August 18th, 2013, 9:05 pm

allstock wrote:

The hpdi unit "appeared" to have Viton propshaft seals, are the two seals the same dimensionally?

Same dimension but like you said...different material.

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

One more thing, the Bob's tab on the OX66 case must be more effective, OR the longer torpedo requires less tab, definitely more crabbing with HPDI case.

OneCycle · **Posted:** August 20th, 2013, 9:35 am

Sounds mainly positive I would say. I gained more top end down pitching when I put the Hpdi case on.

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

OneCycle wrote:

Sounds mainly positive I would say. I gained more top end down pitching when I put the Hpdi case on.

Yes a think going down an inch would have improved overall performance without hurting top end. I would like to see a coned OX66 case with a skeg from an HPDI. I like the bowlift without positive trim of the coned case. I suspect the full modded HPDI case from Hydro-Tec solves these issues. Modified water p/u's, extended bullet, and modified skeg.

OneCycle · **Posted:** August 20th, 2013, 11:09 am

i have some extra setback brackets if you want a llittle more bow lift with the HPDI case?

DoktorC · **Posted:** August 20th, 2013, 11:31 am

Dropping it the inch will probably bring back all your bow lift but I would bet you'll also lose the gained top end.

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

OneCycle wrote:

i have some extra setback brackets if you want a llittle more bow lift with the HPDI case?

I've got 13.5", two more inch's may help but I would be afraid of it porpoising in the midrange.

DoktorC wrote:

Dropping it the inch will probably bring back all your bow lift but I would bet you'll also lose the gained top end.

Tough to say, I've got some rpm range left so maybe not, I know how to find out but I'm still looking for a HPDI case, the one I tried was a loaner.

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Ox66 case vs HPDI

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