adding Extention Box on 251
 

Has anyone added an Imco extention box ( 12" netural) to a 251 convinsor ? What type of "X" dimensions are good for the older ones ? Or has anyone used a 2" shortie lower ? Any comments or history ? Thanks

Re: adding Extention Box on 251
 

I would not do it unless you had twins. The boat will chime walk real bad. The 28 convinsor with extensions is a hot set-up.

Mark

Re: adding Extention Box on 251
 

Had 89 GTX Convinsor with land and sea sternjack, did not chine walk at all but there tough on gimbal bearings.

Re: adding Extention Box on 251
 

Thanks for the comments. Mark why do you say it will chine walk ? ZZZZZZ's the land and sea is totaly different, but how did it run with it ?

Re: adding Extention Box on 251
 

74 GPS, I believe it helped and it's pretty cheap. you might find one used. also helped with the holeshot.

Re: adding Extention Box on 251
 

Allot depends how your boat is set-up. I had a notch transom which allowed for a higher x dimension in my 253. I was also running 710hp at 90 mph which left very little of the boat in the water. I was "running out of boat". The righthand rotation of the motors tend to favor one side. Twin screws counter rotate and keep it balanced. If you don't have a notched transom, then the extension box will make it feel like a big boat(12" longer). The way the water comes from the bottom of your boat and hits the drive and props is critical. Too high you get blow outs and too low you will loose speed. You need the boat looked at to determine if spending the big $ will gain you any speed at all. Just not a big fan of extension boxes on singles. I know you don't want to hear this, but when ever possible, get twins.
Mark

Re: adding Extention Box on 251
 

Thanks for your comments Mark. Your correct I would love to have twins, but I like the current payment, if you know what I mean. My 251 does not have a notched transom ( 87' 251 convinsor ) With the old motor (468 ~550hp) we were running 78mph. The new motor is a 572, 650hp and I hope to see 82-85mph. I bought the box and drives for a reasonable price so I will try one step at at time and see what will work the best.

Re: adding Extention Box on 251
 

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