I/O (Sterndrive) Conversion to Outboards

Lou C

Lou C

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Wow Ted that's amazing.
OK got a new business idea for you....
If you are ever on the Hull Truth, there are always a few threads on inboard or I/O conversion to outboards, and this stability issue is rarely mentioned, I bet you could do engineering consults to determine if the conversion will result in safe/stable seakeeping traits....provided that the owners, are looking for that information....
And looking at catalogs for modern sport boats, so many that now come with both I/O or O/B appear to use the same hull you wonder if the OEMs even went that far with it?
Saw this with Chapparal and Four Winns, several appear to use the same hull.
 
P

Pmt133

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schmutzdecke is one of those words you don't think is real but is used industry wide lol
 
Scott Danforth

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Ted, when you put all the extra beer in the bilge, the CG will be lower
 
tpenfield

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Lou C said:
Wow Ted that's amazing.
OK got a new business idea for you....
If you are ever on the Hull Truth, there are always a few threads on inboard or I/O conversion to outboards, and this stability issue is rarely mentioned, I bet you could do engineering consults to determine if the conversion will result in safe/stable seakeeping traits....provided that the owners, are looking for that information....
And looking at catalogs for modern sport boats, so many that now come with both I/O or O/B appear to use the same hull you wonder if the OEMs even went that far with it?
Saw this with Chapparal and Four Winns, several appear to use the same hull.
Click to expand...
I get over to THT once in a while. There are a few conversion threads over there. Not sure I'd want to do any marine consulting . . . kind of late in life to become a Naval Architect.

It is true (as far as I can tell) that the OB versions of the typical sterndrive boats use the same/similar hull. Although, I have noticed that the OB version are a bit heavier than the Sterndrive models. There is some additional weight in the transom supports, and perhaps they also add some weight down low.
 
redneck joe

redneck joe

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tpenfield said:
I get over to THT once in a while. There are a few conversion threads over there. Not sure I'd want to do any marine consulting . . . kind of late in life to become a Naval Architect.

It is true (as far as I can tell) that the OB versions of the typical sterndrive boats use the same/similar hull. Although, I have noticed that the OB version are a bit heavier than the Sterndrive models. There is some additional weight in the transom supports, and perhaps they also add some weight down low.
Click to expand...
What is percentage of weight differential?
 
tpenfield

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For those following along, here is the calculation for change in CG . . . I previously did a similar calculation for the fore/aft movement of CG.

12in x 1400lbs + 19in x 2250lbs - 12in x 400lbs = 54750 in-lbs

= ? in x (11000-2250+1400+400) lbs

54750 in-lbs/10550 lbs = ?

? = 5.2 inches​
 
harringtondav

harringtondav

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tpenfield said:
Very technical . . . Here is what I Googled . . .

"A wee bit" means a very small amount, degree, or quantity, using the Scottish word "wee" (meaning small or little) with "bit". It's an informal phrase used to say "a little bit,"
Click to expand...
That extra 44+" of planing hull has been in the back of my mind. I'm thinking a good outcome. Hopefully a lower planing speed and maybe being able to abandon the trim tabs.
 
tpenfield

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harringtondav said:
That extra 44+" of planing hull has been in the back of my mind. I'm thinking a good outcome. Hopefully a lower planing speed and maybe being able to abandon the trim tabs.
Click to expand...
I will keep the trim tabs, even though I don't use them much. Speaking of which, I unfastened the trim tabs the other day, just to gain some clearance. There was a stainless steel plate between the trim tab's mounting plate and the transom. It was stuck on with what appeared to be 5200. I had to get a sharp chisel to cut into the adhesive to get the plate off (destroying the plate in the process).
 
Scott Danforth

Scott Danforth

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tpenfield said:
I will keep the trim tabs, even though I don't use them much. Speaking of which, I unfastened the trim tabs the other day, just to gain some clearance. There was a stainless steel plate between the trim tab's mounting plate and the transom. It was stuck on with what appeared to be 5200. I had to get a sharp chisel to cut into the adhesive to get the plate off (destroying the plate in the process).
Click to expand...
Easy to have another laser cut.

It's just 16 gauge stainless
 
harringtondav

harringtondav

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A bit off the main topic, but I want some education about I/O vs O/B in saltwater. I'm freshwater and realize the maintenance simplicity of O/Bs vs I/Os.
I see many/most O/B boats in saltwater. I assume the engine housings are aluminum, but still subject to corrosion, as are the drive hsgs.
Are big saltwater O/Bs HX cooled? Beside the maintenance advantages, what are the other benefits of an O/B in saltwater?
 
tpenfield

tpenfield

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harringtondav said:
A bit off the main topic, but I want some education about I/O vs O/B in saltwater. I'm freshwater and realize the maintenance simplicity of O/Bs vs I/Os.
I see many/most O/B boats in saltwater. I assume the engine housings are aluminum, but still subject to corrosion, as are the drive hsgs.
Are big saltwater O/Bs HX cooled? Beside the maintenance advantages, what are the other benefits of an O/B in saltwater?
Click to expand...
To the extent that I have researched, OB's of all sizes are open cooling (no HX).
Large-OB1.jpg
.
The main advantage with OB's is that you can/should tilt them up out of the water when not in use. This alleviates the issues of galvanic corrosion and marine life growth. Since the lower unit and propeller don't need anti-fouling protection (paint) and are generally not subject to marine growth, they maintain their original efficiency.

An I/O boat that is a trailer queen, rack stored, or always kept on a lift has similar advantages.

Others may have additional comment on the advantages/disadvantages.
 
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