Does the shaft have to be exactly with the transform or can it be 2" longer?

infowire

Seaman Apprentice
Joined
Jun 10, 2018
Messages
33
Hello everyone, i bought my first inflatable boat and i got a mini jacker plate and wondering if i should mount it 6" and leave it as manufacturer specs at 4". My transform is 15". My shaft is 21".
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,118
My transform is 15". My shaft is 21".

Ayuh,..... Welcome Aboard,.... Yer tryin' to mount the wrong motor to a too shorta transom,.....

No matter what ya do, it'll be a compromise that won't be Right,.....
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
What's the Sibs length, OB brand and HP ? Try to raise the OB to sit 5" higher on transom. With well inflated inflatable to factory specs, sit someone up front, trim OB to sit at 90º deg, go for a wot run on calm flat water cond and check if there's water splashing back or over transom, if so, raise OB one, two holes upward till splashes cancels out. Will need to make consecutive water tests raising OB till than cond is met.

Happy Boating
 

infowire

Seaman Apprentice
Joined
Jun 10, 2018
Messages
33
well i raised it to 21" now gotta try it out. It's a chinese 7hp from ebay.
 

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Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
That's a Cat inflatable boat, right ? With OB siting at 90°, that's fully perpendicular to water level raise OB accordingly till water flow passing out middle transom skims right under the small upper splash plate. That's the best spot for prop to achieve top prop thrust with ideal min lower leg drag.

Being such a under powered OB for a Cat once OB's break end period ends install a Hardline induction tach and go for a prop maximization in order to pull wot revs towards max wot rpm range for better hole shot while lightly loaded, would say max 2 light souls on board. If not propped right probably cat will only achieve fast displacement speeds and be hard to plane out. Report your findings...

Happy Boating
 
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