Long Shaft OB on 15" Transom-Performance Questions?...

[BloodStone]

Hello;
I currently have an opportunity to buy a "new 25hp motor" (with controls) at a really great price.
Therefore, I am contemplating putting a long shaft 1991 Mariner 25hp with controls on my modified Meyers 15' Aluminum semi-V.
The transom is roughly 15" or so. A local marine mechanic said that outside of the prop sitting 5" lower in the water, there is really not much difference in performance between a 25hp LS vs a 25hp SS on my boat (he hasn't seen the boat btw).
Is this true? Outside of really shallow water, why do I need a "mini-jacker" plate installed?
And would installing a "whale Fin" on the LS possibly help with getting up on plane better?
Thanks in advance.

 

[lckstckn2smknbrls]

You will have additional drag from the longer L/U.

 

[SumDumGuy]

Unless you get the anti-vent plate at correct height the fin will do nothing more than cause more drag.

 

[JoshKeller]

i have a bracket for sale in the buy and sell section that will solve your problem.

 

[BloodStone]

JoshKeller » Wed Feb 12, 2014 8:39 pm[/url]"]i have a bracket for sale in the buy and sell section that will solve your problem.

Saw it-Thanks!

 

[JMichael]

Just a guess, but I'd say you're gonna lose 2-4 mph off the top end by having the prop that much lower and dealing with the extra drag.

 

[T Man]

I would find a new marine mechanic. The amount of drag caused by 5" of lower unit is huge and can be the difference between planing and not planing.

 

[Gotem]

There is a place that rents 14 foot deep-v mirrorcraft boats near me. I think he bolted a 2x8 or a 2x10 on the back of the boat and caulked around it. This way he could run a long shaft on a 15 inch transom.

 

[longshot]

It will also probably fill the boat with water that will come over the transom from the motor plowing through the water that deep