CG c/w conversion & X theory smaal boat
03-16-2023, 06:47 PM
#11
Registered
Gary, Too much to get into and type. First I hated spinning in with my surface drives,but had to because of attack angle,stern lift spinning out...getting on plane etc.., boat always wants to rollover in any kind of throttling in a sea...but they say you get more bow lift which we all need..,now I have my first round bottom old school v but back to an XR shorty single I/O. 8ft beam though. I loved my 7ft beam boats but much more tender with tab etc. Always had at least a 280 merc k plane. You just have to play with weight mid to forward and find a good balance.
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Twin O/B Sonic (03-16-2023)
03-16-2023, 07:53 PM
#12
Registered
Outonsafari, THANK YOU so much for your input and sorry for hijacking your thread!
Not in any order but, here’s some replies/comments.
Yes my Sonics had round keels so driving them at speed was also a challenge as you’re trying to keep it on a pad that, it don’t have!
I tried a set of Bravo Ones on it and it hopped.
I cut the lip off the hubs same as you and it cured it.
It still would not carry the bow w/them.
I have a GoPro and that is on my list for fact finding.
From before the GoPro era, here is my first 24 Sonic At WFO.
I blew this shot up then drew lines for keel, chine, transom and water line to approximate wetted surface.
Very little!
Look close and you can see the tabs.
The Convincor has a, kinda pad.
15” wide but w/a vee.
In my world a “pad” is flat so….
In theory, (a guy that loves flying fast OB vee’s) this should be easier to drive than the Sonic.
NOT!
I owned rigged, set up, a 100+ mph 17’ Hydrostream, Allison, STV, raced/built kneel down hydros etc, thought I knew how to do this.
Cool thing is, after getting the Convincor to be a really good, weekend cuddy cabin, run 70+, I was out of energy and ready to move on.
Then…I took the winter off to work on my MG and now I’m wired for sound!
Totally rejuvenated.
I think w/stock 225’s I should see 80.
My real love is porting/tuning the motors.
I said at the start that I thought 90 was a legit target but we’ll see.
May not have that much energy left for the project.
At this point extra HPs do nothing.
I will tame the beast!
Not in any order but, here’s some replies/comments.
Yes my Sonics had round keels so driving them at speed was also a challenge as you’re trying to keep it on a pad that, it don’t have!
I tried a set of Bravo Ones on it and it hopped.
I cut the lip off the hubs same as you and it cured it.
It still would not carry the bow w/them.
I have a GoPro and that is on my list for fact finding.
From before the GoPro era, here is my first 24 Sonic At WFO.
I blew this shot up then drew lines for keel, chine, transom and water line to approximate wetted surface.
Very little!
Look close and you can see the tabs.
The Convincor has a, kinda pad.
15” wide but w/a vee.
In my world a “pad” is flat so….
In theory, (a guy that loves flying fast OB vee’s) this should be easier to drive than the Sonic.
NOT!
I owned rigged, set up, a 100+ mph 17’ Hydrostream, Allison, STV, raced/built kneel down hydros etc, thought I knew how to do this.
Cool thing is, after getting the Convincor to be a really good, weekend cuddy cabin, run 70+, I was out of energy and ready to move on.
Then…I took the winter off to work on my MG and now I’m wired for sound!
Totally rejuvenated.
I think w/stock 225’s I should see 80.
My real love is porting/tuning the motors.
I said at the start that I thought 90 was a legit target but we’ll see.
May not have that much energy left for the project.
At this point extra HPs do nothing.
I will tame the beast!
I swear when I’m trying to drive straight it sometimes feels like I’m crabbing, but I can’t be sure.
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Twin O/B Sonic (03-18-2023)
03-18-2023, 06:02 PM
#13
Registered
Yours is twins isn’t it?
If so, shouldn’t be crabbing.
My Hydrostream, the yellow boat was crabbing bad at speed.
Had mechanical steering so easy test.
W/the boat on the trailer, I set the motor straight ahead then put a wire tie on the steering wheel at top dead center then made a pass.
As I cranked in steering correction to keep the mass…,moving straight, I watched the wire tie.
It ended up at bottom dead center!
It wasn’t scary until I put it on the trailer, turned the wire tie to BDC, then stood behind the boat and looked at the motor!
Should have been going in circles!
I modded the gear case and reduced the crabbing by 50% but still was not good.
If so, shouldn’t be crabbing.
My Hydrostream, the yellow boat was crabbing bad at speed.
Had mechanical steering so easy test.
W/the boat on the trailer, I set the motor straight ahead then put a wire tie on the steering wheel at top dead center then made a pass.
As I cranked in steering correction to keep the mass…,moving straight, I watched the wire tie.
It ended up at bottom dead center!
It wasn’t scary until I put it on the trailer, turned the wire tie to BDC, then stood behind the boat and looked at the motor!
Should have been going in circles!
I modded the gear case and reduced the crabbing by 50% but still was not good.
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IGetWet (03-19-2023)
03-18-2023, 07:18 PM
#14
You didn't/aren't hijacking the thread, the discussion is on topic
Man that sonic is way up out of the water. thats the bottom (keel) i thought the checkmate had.
You had those hydrostream pics on other threads and over a 100 was wha t i rememner.
turning the steering wheel that much is insane.
didn't think diffuser rings would induce chinewalk on twins.
About that crabbing i always thought the kplanes were doing it. Wind over/across the strbrd bow was not a factor, maybe beause of a right handed prop.
wind over the port bow caused a wheel turn and port lean, 1 kplane swear to god would push the transom to right in order for boat to run level. Cross a wake and the changing water pressure on the hull would give that 1 kplane double its force and wiggle the boat up bad. But only wind coming over port bow.
Man that sonic is way up out of the water. thats the bottom (keel) i thought the checkmate had.
You had those hydrostream pics on other threads and over a 100 was wha t i rememner.
turning the steering wheel that much is insane.
didn't think diffuser rings would induce chinewalk on twins.
About that crabbing i always thought the kplanes were doing it. Wind over/across the strbrd bow was not a factor, maybe beause of a right handed prop.
wind over the port bow caused a wheel turn and port lean, 1 kplane swear to god would push the transom to right in order for boat to run level. Cross a wake and the changing water pressure on the hull would give that 1 kplane double its force and wiggle the boat up bad. But only wind coming over port bow.
Last edited by outonsafari; 03-18-2023 at 07:23 PM.
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Twin O/B Sonic (03-19-2023)
03-19-2023, 06:32 AM
#15
Registered
Normally, the farther back you go on a OB powered, heavy Vee, the faster it runs.
Here is my 21’ Checkmate Starliner (that I should have never sold!) that I added 18” of set back to.
And was a successful mod.
Although I never got a handle on the motor I built for it, went from feeling like a heavy ski boat, requiring full up trim to get the bow up, to needling only neutral trim to fly the hull like a 500lb Allison!
And back to the Convincor, I ran w/friends in Fla last winter and though they didn’t get pics of it, they said it was on the drain plug at speed.
The problem is getting it there and back!
My 20” mid sections will be here tomorrow and Yesterday I scored a second Lightning gear case.
I have a second one on the project motor from the Starliner and will convert it to LH rotation (as OMC never made one) and install them as well.
Did the same on my last Sonic and looked to be worth +1 - 3 on top.
Plus, that will complete the equation of making it look like a fast boat!
And to your observations above, sometimes, after yrs of doing this, many projects, thinking we know what we’re doing, it’s good to get our asses kicked to remind us there is still much to learn!
On my first 24 Sonic, it ran so good out of the box, I thought, wait till all the tricks I’ve learned!
It should be a screamer!
Rotation, toe in/out, nose cones, etc.
EVERY one I tried, slowed it down!
A couple of points on the OB Vs IO discussion.
If you can make your OBs work on a bracket w/decent set back, you get back the corners of our swim platforms that none of us want to lose.
And this one I’ve not seen mentioned, is jackplates.
For speed yes.
Same as raising your X dimension.
Ive helped a bazillion fast IO boats into dock, in the wind, due to this.
The OBs act identical in the wind.
W/my plates up, in the wind, you better have bumpers out and a good first mate!
W/the plates down, it docks like a fische Bote!
When I go to the 20” mids I will lose a fair amount of that.
Here is my 21’ Checkmate Starliner (that I should have never sold!) that I added 18” of set back to.
And was a successful mod.
Although I never got a handle on the motor I built for it, went from feeling like a heavy ski boat, requiring full up trim to get the bow up, to needling only neutral trim to fly the hull like a 500lb Allison!
And back to the Convincor, I ran w/friends in Fla last winter and though they didn’t get pics of it, they said it was on the drain plug at speed.
The problem is getting it there and back!
My 20” mid sections will be here tomorrow and Yesterday I scored a second Lightning gear case.
I have a second one on the project motor from the Starliner and will convert it to LH rotation (as OMC never made one) and install them as well.
Did the same on my last Sonic and looked to be worth +1 - 3 on top.
Plus, that will complete the equation of making it look like a fast boat!
And to your observations above, sometimes, after yrs of doing this, many projects, thinking we know what we’re doing, it’s good to get our asses kicked to remind us there is still much to learn!
On my first 24 Sonic, it ran so good out of the box, I thought, wait till all the tricks I’ve learned!
It should be a screamer!
Rotation, toe in/out, nose cones, etc.
EVERY one I tried, slowed it down!
A couple of points on the OB Vs IO discussion.
If you can make your OBs work on a bracket w/decent set back, you get back the corners of our swim platforms that none of us want to lose.
And this one I’ve not seen mentioned, is jackplates.
For speed yes.
Same as raising your X dimension.
Ive helped a bazillion fast IO boats into dock, in the wind, due to this.
The OBs act identical in the wind.
W/my plates up, in the wind, you better have bumpers out and a good first mate!
W/the plates down, it docks like a fische Bote!
When I go to the 20” mids I will lose a fair amount of that.
Last edited by Twin O/B Sonic; 03-19-2023 at 06:51 AM.
