Engine Mounting Height for Outrage 22

Optimizing the performance of Boston Whaler boats
Fenx
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Joined: Thu Sep 13, 2018 10:07 am

Engine Mounting Height for Outrage 22

Postby Fenx » Sat Sep 29, 2018 4:44 pm

Hello. I'm just about to re-power a 1988 Outrage 22 with a 2017 Yamaha F225.

Could you give me advice on engine height, please.
Last edited by Fenx on Sun Oct 28, 2018 11:13 am, edited 1 time in total.

jimh
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Location: Michigan, Lower Peninsula
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Re: Engine Mounting Height for Outrage 22

Postby jimh » Sun Sep 30, 2018 7:48 am

Install the engine mounted one-hole-up from lowest. Conduct tests by recording engine speed, boat speed, and fuel flow rate. Observe the position of the anti-ventilation plate while running on plane in the upper range of boat speed. Assess these observation to infer if a higher mounting might be beneficial.

Fenx
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Joined: Thu Sep 13, 2018 10:07 am

Re: Engine Mounting Height for Outrage 22

Postby Fenx » Sun Sep 30, 2018 12:26 pm

Thanks Jim, much appreciated.

jimh
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Re: Engine Mounting Height for Outrage 22

Postby jimh » Thu Oct 04, 2018 9:13 am

Regarding engine mounting height with a bit more elaboration:

It is often cited that mounting an engine at two-holes-up from lowest is also a good mounting height. Whether or not one-hole-up or two-holes-up will be better is difficult to predict for a particular combination of boat, engine, propeller, weight distribution, and sea state. I don't think you can go wrong at one-hole-up, as it is extremely unlikely that will be too high.

A significant contribution will come from the propeller being used, and how well it operates at higher engine mounting positions. Some propellers are probably actually intended to be run at rather high mounting heights, and if run with all blades completely submerged in solid water those propellers may behave as if their pitch were substantially higher than the marked pitch, which might be intended to describe the pitch when running is aerated water.

The only way to know which mounting height works best is to try several mounting heights. Therefore, if after testing with the engine at one-hole-up mounting you are not satisfied with the outcome, you can certainly experiment further with higher mounting positions.