BigSilverCat

We originally had smaller gears and two idler shafts to take away half the load on teeth and bearings. But because of the shaft dimensions, bearing dimensions to clear them and gear to be able to inset the bearings into the gear where it will make the box shorter in length dictated a bigger dia gear so we dropped down to one idler shaft.

There would be more power draw from the second idler gears set and more heat generated. And we may not need it, but would not know till we try with out it.

The cases are easy for me to make so if we break a set of gears I will just make new cases that do have a second idler shaft and still be able to use all the same shafts and gears.

TruxtonFox

I’m sure you have the machining abilities for it, but if not, my brother works in oilfield manufacturing. More specifically fluid ends, turntables, draw works etc. Heavy duty, full load, custom gears are made all the time in house.

1 MAIDEN AMERICA

You make gears, shafts, cases, cut splines, etc. Why not props?

stirling

Think he made a set steel props a few years back for his V bottem Skater, as I understand his stainless props kept throwing blades

SS496

Instead of getting your overdrive ratio from a compounded spur gear set......how about an inline planetary?.... 4000 series allison transmission planetaries (or similar) should have the torque capacity and longevity you are looking for...they would also fit into a smaller envelope...integrate them into your own case ( i realize that would be a complete redesign for you).

the main issue would be ratio selection...unless you make your own.

BigSilverCat

The transmissions are Bam's LHP3000, I have a set of crash boxes and spring adapter plates with there splines if the Bam's do not work, if that is what you were asking?

I have been trying to find a Mercury M8 lower that is broke or taken apart so we could look and measure to see if it would be possible to change the lower ratio. That would keep me from having to add the overdrive box, weight, power loss, ect.

The lower ratio is a 22 tooth driving a 25 tooth. Which is a 1.14 ratio under drive. If I could switch the gear tooth count to 25 driving a 22 it would give me a lower ratio of .88 and an overall ratio of .85 over drive which would be about where I want to be. If we could have gears made and possibly cut the side of case and put a plate over the hole I think it would work and not really cause much drag once were going. It would be the top of the bullet which is out of the water when were running.

Does anyone have a M8 Lower that is broken or taken apart for any reason that I could borrow to measure? I do not want to take mine apart because the engines will be done next week to test the boat. And they are still factory set up which might give them a better chance of living then if I take them apart and put back together.

SS496

Also...for gear box testing purposes you could build a 4 square it allows two boxes to be tested at the same time and at varying levels of torque (whatever profile that is deem necessary) ..... Ive life tested transfer cases in as little as a couple weeks with one.

BigSilverCat

I have egt probes on each cylinder, I'm using a guage for aircraft that has 12 inputs. it is not water proof and the last time I ran it I had just put it in and used clear tape over it to keep water out since it was raining. I just finished the cover for it yesterday. The pics are upside down, I will fix them when I get to a hotel tonight.

HabanaJoe

Tyson - a bit of advice and maybe you are doing it already but you should monitor exhaust manifold pressure (not back pressure but between exhaust ports and turbo) and that should be right along side boost pressure, you know boost has to be higher than exhaust, when it is not the engine can't breath anymore and things melt - again not an expert just years of looking over damage.

BigSilverCat

Our exhaust pressure is 10 - 15 psi less then boost pressure. We are only running 35-40 psi boost, which is nothing for a diesel.