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#1
05-06-2019, 09:12 PM
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25 Seafari Repower Question
Any suggestions on re powering a 25 Seafari with a Stainless bracket?
I'm definitely going Mercury, but working on pro's and con's to a single 300 or 350 Verado, or twin 175 or 200 Four Strokes. The weight is the same for the 175's and 200's - 475 lbs. each 300 Verado - 600 lbs. 350 Verado - 668 lbs. I understand I'm loosing some fuel economy but I'm still thinking security with two motors. I plan on some extended Bahamas trips and that was my thought process. Please let me know if anyone has been own this road. Much appreciated. 
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#2
05-06-2019, 09:39 PM
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Here's one with a 250 ox66 yamaha.
https://www.youtube.com/watch?v=V-W7AI9Tp_w https://www.youtube.com/watch?v=qaF3xQWhHcM If I were you I probably go with a 250 or 300hp v8 Merc when they are available. The 25 seafari hull is narrower than the 23 and only 18inches longer. The weight is about the same as the 23. I might have some real numbers with a single zuke 225 coming soon.
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#4
05-08-2019, 10:56 PM
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Bilgerat sold his 25 with a set of 2.0L Merc 150 two strokes (390lbs each) on a bracket. Those are light engines compared to what's out there today.
Did you read the bigfluke posts from 2007?
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#5
05-09-2019, 07:24 AM
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The 25 is very sensitive to center of gravity changes, both horizontal and vertical. Mine has a 5.7 duoprop with an aluminum platform and kicker. It balances well, but still likes more weight forward. Twins on a heavy stainless bracket put about a net 1000 lbs well behind the transom and several feet higher than an I/O.
Have you done the calculations to see how much the cg would change? Going to a single saves 350 lbs. Might be significant.
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#7
05-09-2019, 02:42 PM
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cdavisdb I've done the basic weight calculations and comparison, but looking for insight on how the bracket will help or hurt that situation and how that stacks up against the twin I/O's that the boat was built with.
I briefly looked at BigFlukes post from 2007. Lot's of info and detail in there. I'll be digging into it more this evening. How does anyone feel about adding more structure to the boat forward, in the way of a hardtop? That will get more weight forward and could help with the extra weight aft, if I were to go with twins. Thanks!
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#8
05-09-2019, 06:44 PM
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Hard top is definitely not a good idea. Even with an aluminum frame, its too heavy to be that high. I have a friend who owned a 25 with two 2 stroke outboards on a bracket that must have been stainless, with a hard top and a tower. He and his wife hated the boat. Raising the cg that much gave the boat a huge roll(to the point that is was scary for an experienced boater) and it snap rolled badly. He took the tower off and it was still bad. Mine has a bimini with aluminum frame to minimize weight. It has a pretty good roll, but its not a fast roll and it does not snap roll. I'm good with it, but somebody else might not be, especially if it was faster and wider.
Bilgerat had twin 2 stokes with a stainless bracket and reported no problems, but he didn't run much in the ocean. I'm not sure how to evaluate that. The 25 has an interesting history. Potter did not build it like Moesly designed it (much less weight forward). To get enough power for the boat to go fast, they needed twin 165's. Compared to my boat, thats 900 extra lbs in the stern. The boat wasn't popular and its my understanding that Potter had trouble getting the boat to act right. Rumors of adding pig iron in the bow. Somebody on this forum posted a formula to calculate cg changes. I've lost it. Anybody remember? Bottom line, be careful with the cg. Extended Bahama trips. Thats exactly what I do with mine. By far, the best boat for that purpose that I've ever owned or been in. If you haven't seen my posts on the early trips, there is a lot of performance information there that you should look at. http://www.classicseacraft.com/commu...ad.php?t=22116 http://www.classicseacraft.com/commu...ad.php?t=24261 http://www.classicseacraft.com/commu...ad.php?t=28890
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#9
05-09-2019, 09:12 PM
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I think Bilgerat had 6-700# in the bow to make up for the CG issue with the bracket and twins. I made a rough 3D CAD model of the 25 and calculated the CG shift between a single I/O and twins on a SS bracket - I don't remember exact numbers but remember it was surprisingly large and that Bilgerat's bow ballast didn't even make up for it. I will try and track that stuff down.
Capt Terry did the CG shift calculator.
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#10
05-09-2019, 10:12 PM
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This was bigflukes KamaII with twin diesels and a fuel tank way forward.
https://www.youtube.com/watch?v=ln3Y1A_RNCM 
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