Re-power 16 SL with modern engine

Optimizing the performance of Boston Whaler boats
oiiuyrs
Posts: 1
Joined: Tue Aug 16, 2022 7:05 am

Re-power 16 SL with modern engine

Postby oiiuyrs » Tue Aug 16, 2022 7:15 am

I have a 16 SL with a 1992 or 1993 Mercury 90-HP two-stroke-power-cycle engine. I want to replace that engine with a modern four-stroke-power-cycle engine.

The Yamaha F90LB has been recommended. I believe the current engine weighs 290-lbs and the F90LB weighs 353-lbs, or 63-lbs more.

Give me your opinion if I should repower my 16 SL with a Yamaha F90LB [with an inference that the concern is the increased engine weight].

Cf.: https://yamahamarinemedia.com/wp-content/uploads/2017/01/F90F75.pdf

[Moderator--this post revived a thread that had been dormant for two years. This post has been moved to begin a new thread on this topic.]

User avatar
Phil T
Posts: 2294
Joined: Thu Oct 22, 2015 6:08 pm
Location: Was Maine. Temporarily Kentucky

Re: 16 SL Re-power at some future time

Postby Phil T » Tue Aug 16, 2022 12:48 pm

I recommend to all owners planning a repower to simulate the new weight in the splashwell before buying new engine.

Take current engine weight, future engine weight, calculate difference. Use bags of sand or water and place in splashwell and drive boat around. Observe trim, static position.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

jimh
Posts: 10790
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Re-power 16 SL with modern engine

Postby jimh » Tue Aug 16, 2022 2:36 pm

oiiuyrs wrote:Give me your opinion if I should repower my 16 SL with a Yamaha F90LB [with an inference that the concern is the increased engine weight].
I cannot give you my opinion because I have not much experience with these older and very light 16-foot hulls with heavier engines. However, a very popular re-power for the somewhat newer 17-foot hull--really the same hull as the older 16, and just a name change--was with a 90-HP E-TEC engine. An E-TEC 90 engine in 20-inch shaft weighed 320-lbs, as far as I can find. The Yamaha F90LB is 33-lbs heavier than that.

A common method to compensate for added engine weight is to move the battery (or in some cases two batteries) out of the stern of the boat and to the console area. A large lead acid battery can easily weigh more than 50-lbs, so moving one or two of them will shift 50 to perhaps 100-lbs or more out of the stern. This will affect the static trim.

The general consideration for a Boston Whaler boat to have proper static trim is that the engine splash well drains are not submerged below the water when the boat is at rest and no one is aboard.

As PHIL mentions, you can easily simulate the added weight with some sand bags or buckets of water in the stern. Observe where the engine splash well drains are now and where they are when you add more weight to the stern. The best place to check for engine weight is to set several 25-lbs sand bags atop the engine cowling.

Some operators of these older 16-foot hulls think a heavy engine is a hazard. See this discussion on engine weight for your boat:

Storm Story: July 17, 2006, Manitoulin Island
http://continuouswave.com/ubb/Forum1/HTML/013113.html

cbards
Posts: 12
Joined: Tue Jul 23, 2019 8:16 am

Re: Re-power 16 SL with modern engine

Postby cbards » Tue Sep 20, 2022 8:31 am

I have a 1993 16SL with 1997 Honda BF 90 at a dry weight of 369-lbs. Both splash wells are above water line, and were even before battery was relocated to the starboard console.

The [maximum boat speed is 40 in what can only be assumed was MPH] with a load [specified only as full] with engine mounted all the way up.

If I ever had to re-power I would like to get a Mercury 115 ProXS with a dry weight of 359-lbs.

The Honda runs like a dream and has for past four years with proper maintenance.

-Craig

jimh
Posts: 10790
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Re-power 16 SL with modern engine

Postby jimh » Tue Sep 20, 2022 1:34 pm

Thread closed. There were no replies or acknowledgements from the originator in over a month. We seem to be talking amongst ourselves.