16 SL with HONDA BF90

Optimizing the performance of Boston Whaler boats
cbards
Posts: 3
Joined: Tue Jul 23, 2019 8:16 am

16 SL with HONDA BF90

Postby cbards » Tue Jul 23, 2019 8:20 am

A 1993 SL16 has a 1997 Honda BF 90 mounted all the way up, and a 13.5 x 15 Honda aluminum propeller.
Engine speed = 6300-RPM WOT
Boat speed = 33 MPH

Give a recommendation on propeller upgrade.

The 16SL now has significant bow rise and porpoising.

biggiefl
Posts: 178
Joined: Thu Jul 11, 2019 1:31 pm
Location: south Tampa Bay area
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Re: 16 SL and Prop

Postby biggiefl » Tue Jul 23, 2019 10:50 am

[A 16 SL was] Not really designed for that [HONDA engine]!weight so that might heighten the porpoising.

Q1: Can any weight be moved forward like battery?

I would probably get same size propeller but SS which may drop engine speed 100-RPM or so—no biggie.

Seems like a small propeller for a 16-foot boat and 90-HP.

Q2: What is WOT range?
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

cbards
Posts: 3
Joined: Tue Jul 23, 2019 8:16 am

Re: 16 SL and Prop

Postby cbards » Tue Jul 23, 2019 3:56 pm

1997 Honda BF90 WOT range is 5000-6000 RPM with a 2.33 gear ratio. leaning towards SS 13.25 x 17 prop

jimh
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Location: Michigan, Lower Peninsula
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Re: 16 SL with HONDA BF90

Postby jimh » Wed Jul 24, 2019 10:12 am

I don’t think a remedy for excessive bow rise while transitioning to plane and oscillating bow while on plane will be obtained by a propeller change.

Reduce weight in the stern.

What is the engine mounting height as described by the number of holes above lowest position?

biggiefl
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Location: south Tampa Bay area
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Re: 16 SL with HONDA BF90

Postby biggiefl » Wed Jul 24, 2019 10:29 am

He just raised the engine mounting, but now the engine speed is exceeding the redline. A 17-pitch should get the engine close to 6,000-RPM.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll:

flymo
Posts: 191
Joined: Thu Oct 22, 2015 2:58 pm

Re: 16 SL with HONDA BF90

Postby flymo » Thu Jul 25, 2019 7:01 am

[The HONDA BF90 engine is] hitting the rev-limiter at 6300 RPM, so to tell what pitch you should be at is hard with that data.

I recommend a quality stainless steel propeller with a stern-lifting design to reduce the porpoising.

Try a PowerTech SCD-3 in a 18-pitch.

You may want to connect with ken@propgods.com. He sells PowerTech (at the best price I have found) and is a good source of specific recommendations.

cbards
Posts: 3
Joined: Tue Jul 23, 2019 8:16 am

Re: 16 SL with HONDA BF90

Postby cbards » Wed Aug 21, 2019 2:57 pm

Update; After working with Prop Gods I installed a Power Tech SCD3 17-pitch stainless steel propeller.

Now has faster acceleration onto plane from a standing start.

[Engine speed was] 6000-RPM trimmed in. And increasing to MPH trimming out before having to slow down.

Still experiencing some bow rise.

Winter projects will

—relocate battery to the port console
—remove the many years of flaky old bottom paint and ——sand gellcoat to shiny.

Thanks for all the advice.