1985 SPORT 11 Engine Shaft Length

A conversation among Whalers
tigerjim1000
Posts: 2
Joined: Wed Apr 20, 2022 11:55 am

1985 SPORT 11 Engine Shaft Length

Postby tigerjim1000 » Mon Apr 25, 2022 12:25 pm

Q1: what components are needed to install a long-shaft engine on a 1985 SPORT 11?

Q2: is there any concern about using an engine with a long-shaft on a 1985 SPORT 11?

BACK STORY
I own a 1986 SPORT 11 with a 1986 Mercury 25-HP engine with short shaft and remote controls. The engine runs--but not very well. [At some unspecified long time in the future] I MIGHT look at a newer engine.

dtmackey
Posts: 760
Joined: Thu Sep 28, 2017 9:29 pm

Re: 1985 SPORT 11 Engine Shaft Length

Postby dtmackey » Mon Apr 25, 2022 2:08 pm

The extra drag of an additional 5-inches of shaft in the water will reduce speed and affect the overall handling of the boat.

It can be done, but it's not a desirable thing in the long term.

jimh
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Location: Michigan, Lower Peninsula
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Re: 1985 SPORT 11 Engine Shaft Length

Postby jimh » Mon Apr 25, 2022 4:19 pm

It will be much less trouble to fix the short shaft engine to run better than it does now. A new engine will be expensive.

There are very few modern engines with short shaft models. At some unspecified long time in the future those engines will be harder to find and more expensive than they are now.

tigerjim1000
Posts: 2
Joined: Wed Apr 20, 2022 11:55 am

Re: 1985 SPORT 11 Engine Shaft Length

Postby tigerjim1000 » Tue Apr 26, 2022 12:01 pm

I have heard of some people using jack plates, but I'm not sure if one would actually mount securely on this boat.

When I get more time, I will continue working on the engine on the boat now.

A really good deal will come along on a newer engine. I want to be prepared.

dtmackey
Posts: 760
Joined: Thu Sep 28, 2017 9:29 pm

Re: 1985 SPORT 11 Engine Shaft Length

Postby dtmackey » Tue Apr 26, 2022 12:49 pm

tigerjim1000 wrote:I have heard of some people using jack plates, but I'm not sure if one would actually mount securely on this boat.


Jack plates are designed to increase performance on boats that have correctly sized outboard shafts. I run one on my 15' Whaler, which is designed for a 20" motor and that's what I run. However, I find that I can run with the motor an additional 5" up with very little lower unit in the water and as you raise the jack plate (it's hydraulic) the attitude of the boat improves with handling and overall feel.

I wouldn't recommend a jackplate as a bandaid for an improperly paired motor with a longer shaft as a jackplate also changes the moment arm (forces on the transom) increasing them and over time this additional force could cause problems.

D-