I/O (Sterndrive) Conversion to Outboards

[Scott Danforth]

I'm going with 425-435

 

[Jmunk]

This is an immense amount of work and I commend you for your attention to detail and the amount of research you’ve put into it. Your drawings are professional and I hope the N.A. was impressed with your knowledge and skill set.

I’ll wager a guess at 412lbs.

 

[redneck joe]

IDK . . . but I'll say 420 . . .

Now that there is a number that makes me happy....

 

[tpenfield]

This is an immense amount of work and I commend you for your attention to detail and the amount of research you’ve put into it. Your drawings are professional and I hope the N.A. was impressed with your knowledge and skill set.

Yes, the N.A. thought that I was "pretty much there" with my design and details. He said that he usually gets hand sketches to work with. Both of us being engineers, we spoke the same 'language', so the conversations went well.

The N.A. did a hydrostatic analysis using some specialized computer software and had these findings . . .

"Effect of the bracket:
The 42" extension of the hull adds planing area aft, which:

• Reduces hump-speed trim
• Improves acceleration
• Softens re-entry
• Reduces porpoising tendency in the 24 to 40 knot range

This aligns with the design intent and is consistent with the powering curves"

 

[tphoyt]

This should be all well worth the effort.

 

[redneck joe]

Random thoughts from a redneck. I aint real stupid but my ignorance can be something to behold....

In my mind Cruisers Inc has always seemed being well built which I'm going to assume is the basis for you adding this many boat unit to it, even given that it appears to be a 90s model when 99% of other boats had quality go to sh.t. They also seem to have been well designed for performance although that is a wee bit out of my area of expertise of which those areas i am good are a very small number.

With the expected improvements in performance (and usable space, etc) what are your thoughts on why they didn't do similar on the original builds? I get that like in your battery conversion that tech has progressed but has there really been that much improvement in hull design in this size boat? I've seen advancements in the 50 plus hull design for planing and speed purposes but a 33 is a commonish size.

Or is the future of boat design just evolving into a system best left to bored old guys?

Kind of an esoteric question but it's early and my wife is out of town and all i have to do today is go paint the new house...

 

[Pmt133]

My thought on why they didn't was simply because at the time, the viability of outboards on a "big" boat wasn't necessarily there. You only really started seeing that come up the last 15 years or so I think. And higher HP outboards that are reasonably light are a relatively new thing as well. Couple that with I/Os getting more complex to service and expensive since 2010 or so and it now looks attractive. Just my thoughts.

Also random thoughts from a dumb kid.

 

[flashback]

I'll guess 475 lbs

 

[tpenfield]

479.4 lbs. . . . more than I was thinking (hoping)

The winner is @flashback

 

[tpenfield]

@redneck joe , @Pmt133 . . .

Just to be clear, the boat is a 2016 model . . . The 328/338 series was introduced in 2014 as a twin engine sterndrive bowrider with overnight capabilities (328 model). It was an extension of the Azure Boat product line, which Cruisers Yacht acquired in 2011. In 2016, the boat was re-badged as the 338 (exact same hull, just an optional swim 'patio' on the back). In 2018-19 the boat also became available in an outboard model with twin Verado 350's.
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Rather than extending the hull, CY merely added a flotation bracket that had the engines mounting at about were the original swim deck ended. To accommodate the engine rigging and tilt space they sacrificed much of the swim deck.
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I am not sure why they did this, because they had to modify both hull & cap molds for the OB versions. They also added a static trim tab at the original transom, indicating that the boat did not have enough hull . . .

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The boat was phased out in 2022 (ish) in favor of the '34 GLS' which is the entry level of the 'new' GLS series. A total of 325+/- '328/338' models were built during its 8-9 year run.

Anyway, since CY modified both top & bottom molds, it is beyond me as to why they didn't add more planing surface, which could then accommodate the engines being further back out of the way of the swim deck.

That has been one of my purposes in doing a custom bracket, and not merely buy a 338 outboard model.

 

[tpenfield]

While I had the extension bracket outside, I did a 'dry run' of installing it to the boat. A few tweaks are needed, based on this trial run.

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Right now I have a single 4x4 along the keel pad to guide the E-B in place. I'll need something more like a cradle so it will have guides on either side as well as the keel. I plan to use a ratchet strap to pull the E-B in tight to the transom.

Otherwise, the combination of the gantry and the shop hoist seem to be OK.
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Once a make a cradle I'll be able to do a full test fit and see where there are gaps. . . as I assume there will some.

Next steps are to:

• Finish the transom laminates
• Do some fairing compound and sand smooth
• Full test fit and gap fixes

 

[Scott Danforth]

479.4 lbs. . . . more than I was thinking (hoping)

The winner is @flashback

View attachment 415182

Holy heavyweight batman

 

[flashback]

This is cool, I never win anything.

 

[Pmt133]

So I guess you can say you added a wee bit more running surface?

 

[redneck joe]

Well I must say for a 2016 boat she have some nice lines. I really thought mid to late 90s.

 

[Scott Danforth]

Not much change in boat stylings over the years...... Pointy end and blunt end with propellers

 

[Pmt133]

Yeah, the last "big" change was the transition to euro styled hull/transom. Regardless, good lines are good lines. Ted's boat has fantastic styling.

4 winns, just as an example, primarily exists because of their design department and what ever cocktail of drugs they were on in the 80s penning those liberator hulls. I still see them out in the wild and think they are up there with some of the nicest styled boats ever built. My horizon is nice but those flat deck sport hull liberators look fast sitting still.

 

[redneck joe]

I like the 'muscle boats' of the 80s

 

[tpenfield]

Garboard Drain ???
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My boat does not have a garboard drain . . . Must be a 21st century thing . . .

During the off-season, keeping the bilge empty is a PITA. Adding the hull extension will only make matters worse. So, I've been thinking about drilling a hole from the original transom into the hull extension once the E-B is fully mounted/secured. Then put the garboard at the end of the extension, so the boat can drain when on the hard. I probably will put a sleeve in the hole between the two to prevent any seepage into the adhesive area of the mating surface. Thoughts?

My main concern is the long-term integrity of such an arrangement . . . basically any movement at a microscopic level forming cracks where the sleeve meets the hull. . . . This might be a @Scott Danforth (and a few others) type of question.

 

[Scott Danforth]

Ted, most of the armstrong brackets have a vertical drain. being aluminum, they simply weld a tapped boss in the aluminum, or if the material is thick enough, just tap the base material.

I would take the garboard drain you show, recess it in the bottom of your keel on the extension. and use one of these



regarding the hole with the sleeve you are showing, I would not do that, however add a second drain to the hull and duplicate what you are doing in the extension since you are already going to be scarfing, tabing, and gel coating

or you can go with the reverse thread version where the plug is inside the bilge.




this is what Cruisers used for decades and what I have on my boat. (I did add an aft garboard plug under the drive because the big block sits over the drain in the bilge)