Time to go prop shopping!

[smbarcelow]

I dropped the Ski Sporter in for the first time this season. I figured I'd be able to get a few more RPM's out of it, having found and corrected the problem causing the misfire/dead cylinder. Well, a few more turned out to be north of six grand! I kept it limited to 5,500 the rest of the time I was out there. I had hit 59 MPH last season at around five grand. With all eight cylinders firing, I'm guessing I'm probably somewhere around 65 MPH (if I don't over-rev it). I'm hoping to take the GPS with me next time.

[BigGrizzly]

I have some props.

[smbarcelow]

Yes, I re-visited the emails we traded last year, Randy. I'm thinking the prop I'm running is a Volvo Ultra 24 (based on some pics Mattyboy posted). I'll have to find out and let you know. Last time we talked, you were thinking I'd probably need a Solas 21. I'll definitely let you know. I think I could twist this one well north of six grand if I wanted to grenade my drive and, possibly, my engine. That eighth cylinder let loose a whole lotta horsepower!

[mrfixxall]

i wing mine to 6200:) but i probably have a little more$ in my engine tho! what drive you running?
Gice john a call at dahpropellers.com, he is the king with the ultra props:yes:

[BigGrizzly]

Wel if you have 350 ponies the 21 is for you if you have 400+ the 23. Most 26 ultras will be same as the 21. Magic Bill has well over 425 hp and turns a 23, only to 5500 or maybe 6000 on his 16 as does his son. In most cases a 21 at just over 5,000 nets you 63mph. on an 18 Donzi.

[MOP]

You can wind the Volvo up a lot more then the black stuff, not that you want to wail the krap out of the engine. But I would not hesitate to push 6K, if it peaks out there then prop down to where your best torque is for your setup.

[smbarcelow]

I've got a GM Performance ZZ4 crate engine that is rated somewhere in the neighborhood of 345 to 355 HP. I'm not sure what year the engine is, so I'm a bit unsure about specs. The previous owner indicated that that Volvo 270 had been rebuilt at the time of the engine transplant. Current ZZ4 specs put redline at 5,800 RPM's. I need to do a little research and see if I can determine where peak torque and peak HP are made. I'd hate to put too much prop on it and make it a dog out of the hole but I'd like to get a good top speed at safe RPM's. I'm still learning about prop drives, as I grew up driving a squirt boat. :D Thanks for all the replies!

[mattyboy]

my goal for a volvo aquamatic boat would be to make a mill that had the cujonez to spin one of grizz's solas 23 to 5000 with a 1.3 gear set

that would be one kick azz ride :yes:

[MOP]

According to this page your peak torque is at 5500, IMO that is what I would prop for. The Volvo drive is very robust don't sweat the drive, I know of a few that have been spinning high numbers for a long time we are not talking black here!

http://www.gmhorsepower.com/350-ZZ4-Turn-Key.php

[mrfixxall]

I've got a GM Performance ZZ4 crate engine that is rated somewhere in the neighborhood of 345 to 355 HP. I'm not sure what year the engine is, so I'm a bit unsure about specs. The previous owner indicated that that Volvo 270 had been rebuilt at the time of the engine transplant. Current ZZ4 specs put redline at 5,800 RPM's. I need to do a little research and see if I can determine where peak torque and peak HP are made. I'd hate to put too much prop on it and make it a dog out of the hole but I'd like to get a good top speed at safe RPM's. I'm still learning about prop drives, as I grew up driving a squirt boat. :D Thanks for all the replies!


you dont want to get to crazy with winging the zz motor like i wing mine like i do, the pistons in your motor dont like constant rpm's..

[mattyboy]

i think 350 horses would have a tuff time spinning a solas 21 to 5500 even at 1.6 i think a 24 ultra or a 21 solas would put the motor right at about 5000

[smbarcelow]

Based on the torgue graph, peak torque appears to be at 3,500, but relatively flat until around 5,250 where peak power is made. I think propping for 5,200 to 5,500 would be about right.

[HallJ]

Marine exhaust kills the power.
The GM power curves are not the same as your current installation.

Jeff

[smbarcelow]

It doesn't seem like logs exiting through hull would kill power, unless you think they create too little back pressure. They can't be more restrictive than a full auto exhaust.

[MOP]

Marine exhaust if anything decreases back pressure, restrictive no!

[BigGrizzly]

Trust me on this logs are not a good way to go. the engine will run more effienctly with an aftermarket or center rise type.

[smbarcelow]

I'd like to get these. I'm not sure whose engine this is, but I know I found the pic in these forums. I grabbed the pic so I could put them on my wish list. [I had made a note that these were CMI.]