engine size and shroud length

[billdoherty]

a friend has an old johnson 25hp. Will the 25.5 be capable of handling the size, weight and power. and does anybody know the lengths of the upper and lower shrouds. it seems they got legs as the boat sat unattended for quite some time.

Thanks
Bill

 

[peptobysmol]

My guess is that it would FAR overpower this boat. I think most would only have a 9.9 HP max.

 

[twalker H260]

shroud length

direct from Marlow-Hunter
http://www.marlow-hunter.com/export...1984_1987/25.5 Standing - Running Rigging.pdf

I would agree a 25hp on that size would be too much. The 26 and 260 were rated for 9.9's.

 

[Deucer]

Bill,

Two issues with this motor and both involve the transom. First is weight. How much does it weigh compared to a 9.9? Will the transom hold it without undue stress? Second, will your transom hold up the that much thrust being put on it? You may severely damage the transom either way.

I can understand the desire of a free or low cost motor. Can't beat that. But remember, no matter how big of a motor you put on, the vast majority of sailboat will only go as fast as the hull speed....for a 25.5, that's probably around 6.5 knots and a 9.9 will push your boat to that speed. With more motor, you'd just be pushing more water around, burn more gas and don't go any faster. If you want a further explanation about hull speed, go here: http://en.wikipedia.org/wiki/Hull_speed

 

[billdoherty]

z

Bill,

Two issues with this motor and both involve the transom. First is weight. How much does it weigh compared to a 9.9? Will the transom hold it without undue stress? Second, will your transom hold up the that much thrust being put on it? You may severely damage the transom either way.

I can understand the desire of a free or low cost motor. Can't beat that. But remember, no matter how big of a motor you put on, the vast majority of sailboat will only go as fast as the hull speed....for a 25.5, that's probably around 6.5 knots and a 9.9 will push your boat to that speed. With more motor, you'd just be pushing more water around, burn more gas and don't go any faster. If you want a further explanation about hull speed, go here: http://en.wikipedia.org/wiki/Hull_speed

 

[billdoherty]

Thanks for the info

z

 

[billdoherty]

thanks to all for the info. don't need to rip off the transom.

 

[Happy Daze]

I have a 5hp long shaft and it pushes ok.

 

[Crazy Dave Condon]

Generally as a rule, the transoms are only designed for up to 10 hp. Anything over that will damage the transom particularly a 25 hp.

Crazy Dave Condon former owner of American Marine & Sail Supply