Seafari 25 Conversion Thoughts on Power?

[FishStretcher]

I think you will want between 200 and 300 lbs ballast by the anchor locker. Squeezing trim tabs around a kicker might be a little tricky. It is said that trim tabs work better in the middle panels, not the outer panels. All the usual tricks like fins and stern lifting 4 blade props are probably the place to start.

[cdavisdb]

I'm not much help on the OBs, but I do have an 8 hp Yammie hithrust on the 25. Very happy with it. Pushes the boat 4 knots into wind and chop and 5+ in calm conditions. This is far superior to the old 15 hp Evinrude I had on the Seabird. It had about zilch low end torque and would not do much at all into wind and chop, and that was with the biggest diameter, lowest pitch prop I could get. .

[Blue_Heron]

I guess I'm late to the dance... My $0.02

• My 25 had a 260hp Mercruiser (blown) when I got it. The PO said the boat would run 40mph with it. My 300HP IO will push it to almost 45 if I prop for speed and run light. Propped for normal use, it cruises at 30mph and tops out around 40 depending on load.

• I did a "back of the napkin" moment calculation once on the CG effect of a single outboard on a bracket, twins on a bracket, and a single V8 IO. Twins shift the CG aft, no surprise. A single OB on a bracket won't move the LCG aft, but it will move the VCG upward. Put a 30gal water tank under the cabin sole and call it good.

• I believe a 250 OB will be plenty of power, but it won't be a race boat. The key to low speed planing will be the prop. If you go Merc 2 stroke, get an Opti, not an EFI. The keel on this boat is deep. You will want a 30" shaft unless you like running the powerhead very close to waterline at idle.

• One advantage of an OB is engine height adjustment. My Bravo drive is mounted about 1/2" higher than recommended by Mercruiser, and it's probably 2"-3" lower than it should be. The steep deadrise angle has a huge effect on correct engine height.

[GameOnSalmon]

Originally Posted by cdavisdb

I'm not much help on the OBs, but I do have an 8 hp Yammie hithrust on the 25. Very happy with it. Pushes the boat 4 knots into wind and chop and 5+ in calm conditions. This is far superior to the old 15 hp Evinrude I had on the Seabird. It had about zilch low end torque and would not do much at all into wind and chop, and that was with the biggest diameter, lowest pitch prop I could get. .

Connor,
Awesome and Thank You that is exactly what I was looking for on the 8hp Yamaha High Thrust. I was considering trying to find a 15 Xtra Long and then Turning it into a High Thrust. That just made my day... Got a 8hp HT Yammie sitting here in the Garage.

Definately Keep You all Posted on the Build out over the next 3 weeks.

Originally Posted by Blue_Heron

I guess I'm late to the dance... My $0.02

• My 25 had a 260hp Mercruiser (blown) when I got it. The PO said the boat would run 40mph with it. My 300HP IO will push it to almost 45 if I prop for speed and run light. Propped for normal use, it cruises at 30mph and tops out around 40 depending on load.

• I did a "back of the napkin" moment calculation once on the CG effect of a single outboard on a bracket, twins on a bracket, and a single V8 IO. Twins shift the CG aft, no surprise. A single OB on a bracket won't move the LCG aft, but it will move the VCG upward. Put a 30gal water tank under the cabin sole and call it good.

• I believe a 250 OB will be plenty of power, but it won't be a race boat. The key to low speed planing will be the prop. If you go Merc 2 stroke, get an Opti, not an EFI. The keel on this boat is deep. You will want a 30" shaft unless you like running the powerhead very close to waterline at idle.

• One advantage of an OB is engine height adjustment. My Bravo drive is mounted about 1/2" higher than recommended by Mercruiser, and it's probably 2"-3" lower than it should be. The steep deadrise angle has a huge effect on correct engine height.

Blue Heron.. Thank You .. Thank You... Your calculations seem to be very close to mine. I spoke to Scott Porta today at Porta Brackets. Will be putting on a 26" 350 HP Porta Bracket in 2 weeks... Scott seems to think this is gonna be one awesome handling boat with the Single 250 on the bracket, I have to tend to agree.

I cant swing the 250 OPTI on Price now... Am working on an OX66 Yamaha from a Guy as well as a 250 Merc EFI from another. If i could swing the cash load on the Opti I would or better yet a 250 H.O. Etec that will have to come next year... The Porta bracket is almost 3k and along with Glass, Resin and all the other stuff I am gonna be 14,000 Into this sucker without much overhaul at this point. With that being said, If i can get her in the water in the next 30 or so days and run it... That should tell me where to start...

And I will be giving out all the data I can so anyone else thinkin about it with a 25' Seafari can... Thanks for taking the time to reply.. Appreciate it.

Robert

[gofastsandman]

Originally Posted by cdavisdb

I'm not much help on the OBs, but I do have an 8 hp Yammie hithrust on the 25. Very happy with it. Pushes the boat 4 knots into wind and chop and 5+ in calm conditions. This is far superior to the old 15 hp Evinrude I had on the Seabird. It had about zilch low end torque and would not do much at all into wind and chop, and that was with the biggest diameter, lowest pitch prop I could get. .

Spoken by one who was there.

[McGillicuddy]

Originally Posted by GameOnSalmon

Blue Heron.. Thank You .. Thank You... Your calculations seem to be very close to mine. I spoke to Scott Porta today at Porta Brackets. Will be putting on a 26" 350 HP Porta Bracket in 2 weeks... Scott seems to think this is gonna be one awesome handling boat with the Single 250 on the bracket, I have to tend to agree.

I ain't doing the math, but I once used a teeter-totter at a Holiday Inn...
Might check with Blue Heron on his napkin bracket calculations. My guess is that he was including a flotation bracket in his calculation rather than a Porta-bracket.

I think Porta-brackets are fine for skinny water and shallow-draft, flat-bottom boats but me thinks this is a bad plan for a 25 deg dead-rise hull that wants is ass end out of the water in the big pool.

I'd talk to Don Herman at Hermco before spending a wad on Scott's product and ruining a perfectly good boat because a rogue wave caught your arse crossing the bar. Just a thought

[GameOnSalmon]

Originally Posted by McGillicuddy

I ain't doing the math, but I once used a teeter-totter at a Holiday Inn...
Might check with Blue Heron on his napkin bracket calculations. My guess is that he was including a flotation bracket in his calculation rather than a Porta-bracket.

I think Porta-brackets are fine for skinny water and shallow-draft, flat-bottom boats but me thinks this is a bad plan for a 25 deg dead-rise hull that wants is ass end out of the water in the big pool.

I'd talk to Don Herman at Hermco before spending a wad on Scott's product and ruining a perfectly good boat because a rogue wave caught your arse crossing the bar. Just a thought

Mcgillicuddy, Thanks for the input... The debate between Twins and Big Singles and the so called Flotation brackets vs non flotation is beat dead.

I for one just look at the math... In a so called flotation bracket you need One Cubic foot of Air to float 63 lbs... Add a 150 lb bracket you need 2.5 cubic feet... Now try and float a 495 lb engine on top of that and you need 10 cubic feet of Trapped air for balanced flotation...

I guess IMHO and it's only an opinion that Flotation brackets cannot create positive flotation... but I will say Don makes Kick Ass brackets for sure but I looked into them and between 3,000 and 4,000 bucks vs the porta with 17 Inches of verticle travel for $2900.00

The main issue is outside of one Person no one has added a bracket to the back of a 25 Seafari... I have to believe that Heron has his #'s right since mine were as close... Even taking into account the so called Cantilever effect the 600 lbs on a 26" Set back is not to far off of 2 outdrives hanging straight out the back and 1100 lbs of engines.... I am going to be really curious to see how she squats once the bracket is on with a 250 HP.

Someone here has to be a Guinea Pig and I am signing up for it... The worst that can happen... I have to remove the bracket, Notch the Transom with a 30" Foot Motor and Glass in a Splash well to Preserve the Integrity of a Full Transom...

This should be interesting to See what happens... can always add some kind of balanced Ballast to the Front as Needed to Level her out...

Thanks Robert

[htillman]

Can't wait to see the results with the bracket and OB installed and the performance with such.

[Blackfin26]

You are brave for taking this on. No expert by a LONG shot but I'd opt for a 300 hp 2 stroke on a notched 30" transom with the splashwell (make the splashwell foldable to give you as much stern room as possible). Then float her and see how she sits. From there you can add/subtract weight along the centerline as needed. Use a 6 gallon portable tank and bring weight to simulate tank placement, etc...Seems the best strategy for doing it once
Best of luck, Steve

[GameOnSalmon]

Originally Posted by htillman

Can't wait to see the results with the bracket and OB installed and the performance with such.

Thillman - Thank You - will start a build out thread 2morrow.

Originally Posted by Blackfin26

You are brave for taking this on. No expert by a LONG shot but I'd opt for a 300 hp 2 stroke on a notched 30" transom with the splashwell (make the splashwell foldable to give you as much stern room as possible). Then float her and see how she sits. From there you can add/subtract weight along the centerline as needed. Use a 6 gallon portable tank and bring weight to simulate tank placement, etc...Seems the best strategy for doing it once
Best of luck, Steve

Blackfin26 - I thought about this a lot, I can always remove bracket and go to a Notched Transom if this does not work... The only Outside cost will be the Porta bracket... So I decided to try this first... If for some reason its a no go... Then the Notch can come... Going with a 30" Foot out the gate.

Look for a build thread to start... Thank You for the Input!