Effect of I/O vs. OB on 25 Seafari CG

[bilgerat]

The COG on My 25 with twin 150 mercs set back 3 ft on big heavy aluminum brackets must be wayyyyy back, the 300lbs of led in the bow helps some but she will still launch off a wave like flipper doing a tail dance!! still rides and preforms better than My old 23 Formula with the IO.

[Bigshrimpin]

Flex - Bigfluke mentioned that his 25 performed best when lcg was 7.9ft from the transom heel. Any idea what size ballast and how far forward you'd have to mount it to achieve lcg 7.9ft from the heel?

[FLexpat]

Originally Posted by Bigshrimpin

Flex - Bigfluke mentioned that his 25 performed best when lcg was 7.9ft from the transom heel. Any idea what size ballast and how far forward you'd have to mount it to achieve lcg 7.9ft from the heel?

Since this model does not have a liner or all the heavy cabinetry and other weight - like seating - scattered (mostly forward) around the boat it will over-indicate how much weight is needed. That said, the primitive model took 400lbs in the anchor locker to get the CG to 7.9' fwd of the heel. Based on that I'm guessing 250-300 lbs in the anchor locker - more if the weight comes aft. Sounds to me like the best option is to convert to a '25 Savage' with the motor under a CC and a jackshaft to a drive - I think that is pretty much what BigFluke did (I'm assuming the 7.9' is without the sponsons he added). An easier alternative might be to have 100' of heavy chain anchor rode and a fresh water tank low and forward. The problem with putting weight in the anchor locker is that the CG gets moved higher so it does not damp out rolls as well.

Bilgerat - PM me your bracket weight/dimensions, motor weights and ballast location so I can stuff that in if you want it for another comparison.

[bilgerat]

Originally Posted by FLexpat

Since this model does not have a liner or all the heavy cabinetry and other weight - like seating - scattered (mostly forward) around the boat it will over-indicate how much weight is needed. That said, the primitive model took 400lbs in the anchor locker to get the CG to 7.9' fwd of the heel. Based on that I'm guessing 250-300 lbs in the anchor locker - more if the weight comes aft. Sounds to me like the best option is to convert to a '25 Savage' with the motor under a CC and a jackshaft to a drive - I think that is pretty much what BigFluke did (I'm assuming the 7.9' is without the sponsons he added). An easier alternative might be to have 100' of heavy chain anchor rode and a fresh water tank low and forward. The problem with putting weight in the anchor locker is that the CG gets moved higher so it does not damp out rolls as well.

Bilgerat - PM me your bracket weight/dimensions, motor weights and ballast location so I can stuff that in if you want it for another comparison.

2 merc 150s weigh 404 each, Im guessing the brackets weigh somewhere around 200 to 250 lbs and they have a 30" set back, she also has a 1/4" aluminum plate that is screwed to the transom for support , its 3' tall and 7' wide, it prob adds some weight

[FLexpat]

OK - seems like there is enough interest in this so I will go ahead and make a model of the liner to get the overall model more accurate and then put together a model with OBs on a bracket. If anyone has photos, drawings, or dimensions of the stringers and hull panels (steps) that would help.

[flyingfrizzle]

Mine will have two 395lb 2.5 mercury 200 hanging off the back on a bracket with minimum set back of about 22" to get the motors to tilt enough for road transport. The bracket will be likely at least 165lbs due to the large floatation chamber. The lay up is a little heavy so may end up more around 185lbs. I haven't tried to weigh it yet but may try to do so once I get the swim platform bond down to the other half. I know Im asking for trouble and do have some tanks that I am going to cut down and add under the cabin floor and in the nose section for water ballast. Mine has the larger head room with more drop down than the earlier models so there may have to be some give there to fit the tanks. Going to be hard to come up with 400 plus pounds with out lead. I do have some ballast bar lead that I use in my race car that I can move around to play with the cg but not enough space to contain all the weight. Plus I don't want to make it a pig either. It is already a heavy hull to start with. The large tank mid ship will be shortened and moved far forward as possible but not much help there as I will still need the capacity for the twin efis. There is a guy with twin 150s with an yellow hull in VA and if I remember he said he had 30 or 32 inches of setback on his and clamed it to ride fairly good but his fairly good may be different than mine or others. I have even thought about adding bladder tanks under the bedding section for additional fuel or water to help but then you loose you storage that is already limited. There will be tons of storage aft where the old io sat but adding fish and ice there will defiantly be a negative effect.