383 / Alpha prop selection

Reply Subscribe

Thread Tools

04-25-2020 | 08:48 PM

#21

Team gone again

Registered

Joined: Apr 2020

Posts: 5

Likes: 0

Quote:

Originally Posted by BUP

Your Alpha gear ratio is set up for a V6 190 hp stock mercruiser engine.

Gear ratio also effects where peak torque will land for rpms.

Most marine engines peak torque lands around 70 - 75 percent of max load.

so what would you recommend I do ?

04-25-2020 | 09:00 PM

#22

speicher lane

Registered

Joined: Jul 2007

Posts: 3,336

Likes: 857

Quote:

Originally Posted by Team gone again

hi I have a 24ft crestliner nortic, when fully loaded we are about 6,300lbs just shaped engine to a 383, with 425ftlbs from 2k and on rpms and 398hp at 5500rpm. We have an alpha one with 1.84 gears and a 14 5/8"x 23p 3 blade prop and get to 42 @ wot 5500 but have lots of throttle left? Any ideas on what prop I should get. Thanks

How can you be at WOT and have throttle left? Or, are you stating the engine is maxed out in "safe operating" RPMs well before Full throttle?

1" pitch is approx. 200 rpms....In your case going from a 23P to a 25P will drop 400 RPM, a 27P prop will drop 800 Rpm

04-26-2020 | 07:49 AM

#23

Team gone again

Registered

Joined: Apr 2020

Posts: 5

Likes: 0

Quote:

Originally Posted by speicher lane

sorry yes we are staying at safe operation rpm, we tried a 27p ballistic 4 blade and lost about 4mph top end at 5500rpm and still had throttle left.

04-27-2020 | 06:45 PM

#24

bbladesprops

Offshoreonly Advertiser

Joined: Jun 2003

Posts: 3,878

Likes: 47

From: Princeton, Wisconsin

I would test a known stock Mercury 25 Mirage Plus and learn from that.

Brett

__________________
Brett Anderson / BBLADES Professional Propellers
920-295-4435 http://www.bblades.com/
[email protected]

04-28-2020 | 12:11 AM

#25

BUP

Banned

Joined: Jul 2011

Posts: 9,594

Likes: 46

From: Ft. Worth TX

Wrong gear ratio for the app. Like I said for an alpha outdrive Standard gear ratio for a V 6 190 hp is 1.84.

also the alpha gen 2 is rated for 300 hp only. The 6.2 L - 377 cid at 320 hp will not ever come with alpha outdrive. All the OEM Merc 6.2 s comes with Bravo s that are sterndrive apps.

04-28-2020 | 05:10 AM

#26

Team gone again

Registered

Joined: Apr 2020

Posts: 5

Likes: 0

Well I just purchased the 1.5 upper with HD gears ill get back with some more info.

05-04-2020 | 03:04 PM

#27

Team gone again

Registered

Joined: Apr 2020

Posts: 5

Likes: 0

Well did a test run with the new upper! With a 23p 3 blade we got to 43mph @ wot 4500rpm. With the 19p got to 38mph @5000rpm with throttle left. Both have about 35% slip any ideas on how to get slip lower. Gonna try a 21p this week to see what happens.

05-04-2020 | 08:41 PM

#28

bbladesprops

Offshoreonly Advertiser

Joined: Jun 2003

Posts: 3,878

Likes: 47

From: Princeton, Wisconsin

You are more than welcome to call us and we can start from the beginning and give you our advice as to the best next move considering your performance goals.
Sometimes, forum discussions can't get to the point or the ending.
There are always many variable involved.

Brett

__________________
Brett Anderson / BBLADES Professional Propellers
920-295-4435 http://www.bblades.com/
[email protected]