kidturbo

That's good info to know. In watching some other videos, I realized the boat speeds up in steps. Once they break loose again up at about 25mph, it takes em forever to hook up again unless you really spin the RPMs. Which I'm trying to avoid. But that's how I got it to shift and hold on plane over 50mph before our transmission issues. Now I'm attempting to bring shift RPM range down to something reasonable. Would be nice to have a set of big 18" 6blades to see if they hook up better at these slower shaft speeds. I need about 6-8mph more speed to get fully on top of the water before changing gears.

thisistank

Saw this and thought of this thread.

1,000 hp.

green lightning

The two issues I think you are fighting are your prop speed and your prop choice , anytime I put my boat on plane I have to bring the RPM's up to 3500 the prop will slip for a few seconds and then the props will bite the RPM's will drop down to 2500 and then she will take off , If I just brought the RPM's up to 2500 and held it there it would never get on plane.

green lightning

green lightning

That video was from a few years ago when i was checking engine RPM's and the boats ability to get on plane

kidturbo

Thanks for the data an video. What gear ratio are you running on that setup?

While in low we are at 1.75:1 ratio, and with the 30P props, it just not getting up on top the water by 3500R. It did when I pushed em to 4500R and held, they finally hooked back up and jumped about 17 to 47mph or above. Once shifted the RMP fell to a level the turbos stayed lit, and it took off from there. Until it puked out trans fluid and I backed off. Unfortunately I have like zero data from that run.

These past few attempts I tried holding boat up by pushing the tabs down [280 k-planes] and then shifting. In attempt to keep props loose until after the shift and it has time to recover. However soon as it shifts, the props hook up again instantly, and the load is to much to overcome at current fueling and boost. Which is about 15psi before the shift..

So question is, do we go much bigger pitch and see how that works, or go up in blades and see if they respond better? While testing the 17x32 6 blades in FL the boat felt great down low speed, but soon a it nosed over, those props were done and not coming back even after shifting and spinning the shafts 4k.

Plan to get back on water over the weekend and test everything we have available. Fixing a couple issues today like header bolt/nut backed off on Stbd manifold, and some electrical interference on Port causing a high RPM misfire. Main reason for not just reving them back up to 5k until they hooked. But our goal is get them on plane, with rev limiters set to 4k.

green lightning

My gear ratio is 1.32 , in the video I was spinning a set of 4 blade 17 dia 35 pitch 15*rake props the best props that I have tested so far have been a set of 5blade 18dia 31 pitch 20*rake they made my planning time a lot shorter .

kidturbo

Thanks very much that info. Maybe I'm expecting to much out of this drive setup down low. Will see how these 32's do in comparison. Maybe even try the 17x34's again now that I know what not to expect. With no engine cover, those big turbos get a bit ear itchy at 4 grand and makes the seconds fly by.. Never remember the ear plugs until I reach about 3400r.

payuppsucker

I’d try some 18 x 34 if you can find some. You have plenty of torque, turning them shouldn’t be a problem.

hoodoo

Ive got 18 34’s in a crate your welcome to try.
If I ship them please find the two lmm ecm’s in the crate.lol
They need vat’s deleted when you have a minute.
I’ll be ready to splash mine as soon as Ryan wires up the ignition harnesses.