BBIII design mods needed

Huntindave McCann

Huntindave McCann

Well-known member
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As some on here may recall, last fall I purchased a BBIII from a member on the east coast. The hull was built "to print" and the workmanship was done well. TO BE VERY CLEAR: I am not trashing the original builder. I knew certain mods would need to be done and took that into account during the purchase.

I've done my homework and am well aware of some issues and mods that have been documented here on this forum. Unfortunately a lot of the previous postings, are incomplete and missing pertinent information. I'd appreciate it if some of you will share your experience, so I don't have to reinvent the wheel. Thanks

What I need to do;
(A) trim the corners of the motor well, to allow for full clearance of the motor, throughout the range of tilt.
Seems to be fairly straight forward to mark the interference and trim as needed. Any pictures or dimensions of what worked for you would be appreciated. Again; BBIII w/ 25 hp Yamaha 2 stroke

(B) address the porpoising issue.
Plan is to add wedges on both sponsons. (sp?) Should I also add some wedges along the leading edge of the motor well? Again what has worked for you? Thickness and length of wedge bow to stern ? Does a longer or shorter angle make any difference or is the height of the wedge the only determining factor?


(C) address the issue of water splashing up and into the cockpit from the motor well.
Plan is to add a splash guard around the lower end of the motor. Debating on just where to position it height wise. I am thinking, lower would be better for controlling splash when moving in a forward direction. Yet a higher position would be better to prevent "wash over", when the engine is in full reverse.


Again, would appreciate some feedback on what is working for those that have already addressed these issues.

THANKS
 
I added splash guards to my BBII...Low as I recall. But that was 9-10 years ago... Have you tried running it? I did not have issues with interference on the BBII, and a Yamaha 25 hp 2 stroke.
 
Huntindave McCann said:
(A) trim the corners of the motor well, to allow for full clearance of the motor, throughout the range of tilt.
Seems to be fairly straight forward to mark the interference and trim as needed. Any pictures or dimensions of what worked for you would be appreciated. Again; BBIII w/ 25 hp Yamaha 2 stroke
Click to expand...
My trimmed off pieces looked like little 3"x3" pyramids. Like you said, mark the interference points and connect the dots. If you take much more than what I did you may end up going through the plywood and fillet joint. If that happens I'd cut another inch or so off and cap with plywood and glass over.

Huntindave McCann said:
(B) address the porpoising issue.
Plan is to add wedges on both sponsons. (sp?) Should I also add some wedges along the leading edge of the motor well? Again what has worked for you? Thickness and length of wedge bow to stern ? Does a longer or shorter angle make any difference or is the height of the wedge the only determining factor?
Click to expand...
Don't add wedges along the front of the motor well, just the sponsons. If any trailing edges are rounded then square them up with thickened epoxy. You want water coming off the back of the boat as clean as possible. The size of the wedges depends on how bad the porpoising is. A little wedge goes a long way. Something along the lines of 3-4" wide and 3/8" thick may be all you need. Make them flush with the sides of the sponson. Fair them in and keep the trailing edges square and clean.

Huntindave McCann said:
(C) address the issue of water splashing up and into the cockpit from the motor well.
Plan is to add a splash guard around the lower end of the motor. Debating on just where to position it height wise. I am thinking, lower would be better for controlling splash when moving in a forward direction. Yet a higher position would be better to prevent "wash over", when the engine is in full reverse.
Click to expand...
Higher is better. Above the cavitation plate and below the motor bracket. On my Brant's current configuration I just added 1x3 mahogany strips to the sides of the well. Nothing along the back was needed. In an earlier version I made something akin to a three sided "horse collar" from 3/8" ply and it worked nicely.
 
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Phil Nowack said:
I added splash guards to my BBII...Low as I recall. But that was 9-10 years ago... Have you tried running it? I did not have issues with interference on the BBII, and a Yamaha 25 hp 2 stroke.
Click to expand...

Phil,
Yes, been out fishing several times playing with pin position, cargo position/layout and such. No issue in two lowest pin positions except when using shallow water feature. At that point is where the interference begins.

I made a cardboard template and cut out a trial splash guard just now. Need to secure it temporary in place and give it a run.


View attachment 20180319_130117.jpgView attachment 20180319_130100.jpgView attachment 20180319_130150.jpg
 
Eric Patterson said:
Huntindave McCann said:
(C) address the issue of water splashing up and into the cockpit from the motor well.
Plan is to add a splash guard around the lower end of the motor. Debating on just where to position it height wise. I am thinking, lower would be better for controlling splash when moving in a forward direction. Yet a higher position would be better to prevent "wash over", when the engine is in full reverse.
Click to expand...

Higher is better. Above the cavitation plate and below the motor bracket. On my Brant's current configuration I just added 1x3 mahogany strips to the sides of the well. Nothing along the back was needed. In an earlier version I made something akin to a three sided "horse collar" from 3/8" ply and it worked nicely.
Click to expand...

Eric,

Thanks for the good info. See the above reply for what I whipped up today. I'm about halfway between min and max mounting positions. Using the same pattern and cutting wider will make it sit higher in the motor well. I started where I did because that was the size of board I had. [sly] Now I need to scrounge up some temp mounting clips and give it a test run.

I am hoping to cut the corners, add the wedges and splash guard all in one shot to minimize manhandling the hull several times.
 
That looks good. You will also want it level or maybe angle it up slightly as water exits so as not to "trap" water.
 
Eric Patterson said:
That looks good. You will also want it level or maybe angle it up slightly as water exits so as not to "trap" water.
Click to expand...

Eric,

I ended up "tabbing" in place with a hot glue gun. The present location is right at the "at rest" waterline. Trial run was good. 100% effective in preventing the splashing from reaching the deck/ top of transom. As I suspected, I still got some "wash over" when in reverse. However the trial plate did reduce the wash over to a point where it was not going over the top of the transom. I will cut a wider piece and raise the location as high as possible under the engine mount. The new location will put the plate above the waterline when at rest.

As to being level, I cut it such that the splash plate runs down hill towards the open end. Trailing edge is about 3/4 inch lower than the leading edge. I wanted it to drain and avoid ice build up.
 

Dave:

You may have already seen these but this is a link to show pictures of how I trimmed the corners on my BBIII. I can't remember how I decided the geometry to make the cut but remember cutting them off with a Japanese saw and finishing to the lines with a belt sander. Went back and patched with 3/8 ply and thickened epoxy and sanded the edges smooth. I know someone on the site shared with me the dimensions to cut but could not find that post.


http://www.duckboats.net/cgi-bin/forum/gforum.cgi?post=154806;do=post_view#p154806
 
David Wheeler said:
Dave:

You may have already seen these but this is a link to show pictures of how I trimmed the corners on my BBIII. I can't remember how I decided the geometry to make the cut but remember cutting them off with a Japanese saw and finishing to the lines with a belt sander. Went back and patched with 3/8 ply and thickened epoxy and sanded the edges smooth. I know someone on the site shared with me the dimensions to cut but could not find that post.


http://www.duckboats.net/...do=post_view#p154806
Click to expand...

David, Thanks for the link, my earlier search did not turn up your thread so this helps. I fully anticipate doing exactly as you and capping the corners. I'd like to think I can do this without flipping the hull, but I know that is delusional thinking,,,,, sigh.
 
Phil Nowack said:
Just lay on your back and keep your mouth shut... You should not have to flip the hull.
Click to expand...

Phil,
Laying on my back to work on something is unfortunately not a good option anymore. In my younger days I could and did, work in most any position wrenching on various pieces of equipment. Now days I can't even slide under the truck on a creeper without actually getting physically nauseous. In a word it sucks, but what can I do?

I had to replace a kitchen faucet a while back. Got the job done but felt like sh*t the rest of the day.
 
Dave

Looking at your pictures again I would narrow the width of the collar. I think 2-3 inches is more that adequate and it doesn't hurt to leave a little more room for the motor. You or someone else might one day run a different motor and need a little more room. It probably only takes an inch or less to stop the water anyway.

Eric
 
Eric Patterson said:
Dave

Looking at your pictures again I would narrow the width of the collar. I think 2-3 inches is more that adequate and it doesn't hurt to leave a little more room for the motor. You or someone else might one day run a different motor and need a little more room. It probably only takes an inch or less to stop the water anyway.

Eric
Click to expand...

Eric,
Thanks for your thoughts. The photos may be a bit deceiving, I've got at least 1/4 inch clearance minimum, that is a country mile to a machinist. [;)] I understand your point about a possible motor switch. Don't see that happening except in case of major damage to this one.

Just for reference, the width on each side is 4 inches. I do want to move the plate up to just under the motor mount. This means the overall width of the splash plate will have to increase by around 3/4 inch to span the opening. I think what I will do is split the present pattern and add the material in the middle. This will leave the width on each side the same, yet increase the motor clearance to 5/8 inch on each side.

I really want to keep the linkages and such of the motor as dry as possible. On other boats in the past, I've experienced problems with things freezing up in zero degree temps. Almost got stranded on a fishing trip one time. Could not pull the starter cord because I had left the gear shift in forward gear. Took a bit of persuasion and cussing, but I was able to bypass the safety, so I could start the engine while in gear.
Another time when duck hunting, got the engine started but could not move the shifter. Had to let the engine heat warm everything up for about 15 minutes before I could move.

The things we do in the name of relaxation.
 
For water splashing, would one of those things walleye fisherman put on the back of their boats to prevent water from coming in the back when backtrolling work? No idea, just throwing it out there. I have seen some that are not rigid but flexible. Made out of silicone I would guess. Could you mount these and trim to fit?

Mark
 
Mark W said:
For water splashing, would one of those things walleye fisherman put on the back of their boats to prevent water from coming in the back when backtrolling work? No idea, just throwing it out there. I have seen some that are not rigid but flexible. Made out of silicone I would guess. Could you mount these and trim to fit?

Mark
Click to expand...

Mark, The splash guard shown above is a better choice and is quite effective.
 
Phil,

"I had to replace a kitchen faucet a while back. Got the job done but felt like sh*t the rest of the day."

I'm glad i'm not the only one with this dilemma, but I really thought him keeping his mouth shut would be the real problem!!

George
 
George Goodsell said:
Phil,

"I had to replace a kitchen faucet a while back. Got the job done but felt like sh*t the rest of the day."

I'm glad i'm not the only one with this dilemma, but I really thought him keeping his mouth shut would be the real problem!!

George
Click to expand...

George,
I was doing a good job of ignoring that detail until YOU couldn't keep YOUR mouth shut! [ninja]
 
Just an update; Moved the splash guard further up to just under the motor mount. Set up my band saw to cut an 8 degree angle and ripped out a couple temporary wedges which I glued to bottom of the hull with hot melt glue. Went out for a test run and was extremely pleased with the results.

The splash guard worked fine in both forward and reverse. Once the weather warms up and I get some epoxy ordered, it will become a permanent addition to the hull.

The temporary wedges I cut came out at 2 3/4 inch leading to trailing edge and 11/32 inch thick at the trailing edge. The wedges eliminated all porpoising and had no adverse effect to top end speed. I am ecstatic and will cut a set of duplicate wedges for permanent duty.

Now I need to take a saw to the corners for motor clearance. That may have to wait a day or two. We are forecast to receive 3 to 7 inches of snow overnight.
 
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Rather than trimming the corners, have you thought of maybe looking at a standoff plate to set the motor back just enough to clear the corners? might also help negate the need for the wedges also.
 
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