25' Checkmate Convincor I/O to twin O/B's

[Instigator]

After taking a break to work on my MG, I am refreshed and ready to get back on the little stuff on the Convincor after struggling through project burn out.

I reversed rotation on the motors to help settle handling have decided to convert to 20” motors.

Installed a stereo too!

Ordering head liner material today to finish the cabin.

The boat came w/o the drop out hdwe for the bolsters and ordered foam to convert them to sit down, for now.
The Mrs much prefers that as well.

We do enough miles on Lake Erie that it is a totally different ride on your asss than on your feet.

On the 20” motors, they will look way better too.

25’s were fine on the wider 24’ Sonics but look like crap, from behind, on the narrower Convincor.

Doesnt even look normal w/the gear cases switched!

[MODVP22]

They look like 30” shafts from the back lol. From the side they don’t look as tall, hmm.

[Instigator]

Agreed Tommy.

[mrichartz]

20s are the way to go... What handling problems are you having? Really interested in how its going to handle at higher speeds with them turning in on yours..
With mine it was definitely interesting getting on plane and hitting the gas at speed (i forget how fast but wasn't much luckily 40 50) the back end just lifted up more and snaked back and forth hard only tried a few times..bow wasn't lifting enough that once the stern lifted more i think it just plowed into the water it was 10 years ago and definitely remember that..because it was so ****ing violent its scared the hell out of the guy with me well me too literally felt like it was going to throw someone out of the boat..not sure if i could have eased into more but wasn't going to bother..mines setup different you got different props etc so. ???.. how high will the motors be up and down w the 20s? You also have alot more setback w the platform..

[Instigator]

W/the motors full up, the prop shafts are even w/the pad.

Which means they’re approx 4” bellow the bottom in front of them.

W/my 26” Rakers it jumps on plane w/o slipping until just on plane then it rolls to starboard.
Hard!

Down tab on stb side cures that.

Basically from 0 - about 45 I run almost full down tab.
I dial in up trim and it flies the bow pretty well, even w/92 gls fuel which has pretty much been the case in all testing/running.

As the tabs are at far corners of transom, they’re out of the water anyhow.

Im still coming to terms w/pulling the tabs and flying the boat w/o them.
It pretty much flies like an Allison.

The issue comes when you back out of the gas w/the tabs up and the bow in the air.
It goes into a violent hop that will scare the baJesus out of you!
I think I was 100% vertical last time, at 50 mph!

I think the trick is to drop the tabs as you slow.

But to choreograph that you need a ton of space which I don’t have around here, w/o going to Lake Erie which is normally too rough to light it up.

Did more on the Suwannee this winter than anywhere else but then you’re dealing w/turns.

Honestly I feel like w/an hr on a long straight river I’d have it.

Basically what the boat wants at 50, changes for 52!
Ive seen 75 once, lightly loaded, right before it tried to kill me and 71/72 multiple times on short bursts but w/92 gls fuel and 15 of water in the anchor locker.

Clear as mud?

[MODVP22]

Hmmm, you do have Jack plates….at idle you could raise them easier to hear them bark if they were shorter 20s instead of 25s

[Instigator]

I run w/the plates full up unless I’m docking in the wind.

Pretty much playing w/tabs and trim only.


Played w/the plates to fight the hop but didn’t seem to matter.

Hmmm, you do have Jack plates….at idle you could raise them easier to hear them bark if they were shorter 20s instead of 25s

[V-bottom]

I prefer the look of 20" mids - but the 25" are more practical if just cruising around most of the time. As soon as I came off plane or just cruising around I would just raise the engines 5" on the lifts

[mrichartz]

Oh your motors are alot lower than mine.
mine are 2 1/2 below 2 1/2 above right in front not the pad
And you've got what 25" of setback w the platform?
Have you run it much with less than 35 gals of fuel?
You've definitely got more weight..

How much did you say yours weighted and that was dry?

Wonder why it rolls hard to starboard like that??

Yea with twins theres nowhere to put tabs so they actually do anything after getting on plane...
Damn you have to run them all the way down?!
Thats the reason i made my tabs 20" just to get more contact once it came up..and so i didn't need to drop them down as far...it definitely made a difference on how much i had to drop them and wasn't as much drag..actually checked speed etc before and after and was faster i mean same rpm and was faster.. less drag..
If that makes sense..
Sounds stupid but back when i was tweaking stuff was curious if a small tab in the middle would work at least it would have contact all the time.. i didn't have a problem with side to side..

Oh where do you have your trim switches? Was trying to find the the picture
i remember trying to use them where they put them factory and wasn't exactly easy actually just a huge pain the ass made juggling look easy... I moved them next to the throttles so i could actually use them..
Still thinking im going to move them in front of throttles.

[Instigator]

Based on the contours at the upper corners of the transom, this limited how high I could go w/my bracket w/o narrowing it, which I did not want to do.

That put motor height right between 20’s w/no Jack places and 25’s with.

I am also close to max motor height w/o going to nose cones, which I don’t want to do.
When I go to 20” mids, I may consider building another pair of Lightnings.
BTW, cavitation burns at intakes lowers shows I’m close.

And I have been thinking similar on extending the tabs.
I even had to go to short rams due to limited install space.

Feels good to have a second wind for the project.

Was close to selling last fall.

[V-bottom]

And I have been thinking similar on extending the tabs.
I even had to go to short rams due to limited install space.

.

I made my own tabs using the stock Bennett shocks and lines from the original tabs. The stock length was 12" so I formed up some new plates @ 16" long and a little narrower - I think 10" wide and it made a big difference getting out of the hole and mid range speed to keep the nose down. The rams were still able to handle the extra 4" length without any trouble.

[Instigator]

Great input.

I looked at that at initial rig but decided to get it wet first.

I have sport tabs w/the double rams too.

I made my own tabs using the stock Bennett shocks and lines from the original tabs. The stock length was 12" so I formed up some new plates @ 16" long and a little narrower - I think 10" wide and it made a big difference getting out of the hole and mid range speed to keep the nose down. The rams were still able to handle the extra 4" length without any trouble.

[V-bottom]

What props are you finding work best for you? Are yours spinning in or out?
My 2 sets of props were 25p 3 blade mirage and 24p bravo 1. The bravo 1 props were best for all round. The mirage were good for a few extra mph top end. I ran them spinning in.

[Instigator]

Been spinning out, just changed to in but haven’t run it yet.

I have six sets of wheels for it but so far have stuck w/old reliable, 26 Rakers.

So far the boat has been such a handful to drive that I wouldn’t learn anything anyhow, unless it helped tame it.

And watch for a set of Bravo Ones.

Ran a set on my old 24’ Sonic and it didn’t like them.

What props are you finding work best for you? Are yours spinning in or out?
My 2 sets of props were 25p 3 blade mirage and 24p bravo 1. The bravo 1 props were best for all round. The mirage were good for a few extra mph top end. I ran them spinning in.

[V-bottom]

Mine was a little quicker spinning out - but too sensitive and unpredictable in messy water. With the motors spinning in and using the nice capilano helm you could cruise along at 50 mph with zero effort at the wheel....dare i say it was almost boring to drive it was so easy.