Originally Posted by survivor25
yea I will be severly ovrpowerd but there will be a limit stop to the throttle and it will only go so fast I am not looking to go faster into a wave only to not be "pushed" back by it. its all just a hobby anyway and no one will have one like it. lol hull speed
on this thing is only 18 "mph" anyway so...
Hull speed is 18 mph??? you have an 18 foot sailboat that has a hull speed
of 18 mph, does it have a keel
? is it a displacement hull
? if so then the calculation that I have seen to find hull
speed is HS=1.34x(sqrt of LWL)
Hull speed - Wikipedia, the free encyclopedia
So, if you assume that the LWL is 18 feet (obviously, it will be shorter than that) you would have a hull speed of about 5.7 knots, or about 6 mph.
Next thing to consider, an 18 foot sailboat will not take much effort to get up to that speed. I have a 32 foot Hunter
is an 18 Hp Yanmar
, 2 cyl. Hull speed is a bit over 7 knots. The engine
will get me to a pretty comfortable 6 knots. With the sails
, I have on occasion seen 7 knots. I have a friend with a 34 foot hunter
and a 30 Hp Yanmar
, he has a hull speed only very slightly higher than mine and he can easily get to 7.5 knots with the engine. My boat weighs in at around 9700 lbs. I can not imagine that you would be able to ever get a significant load on an 18 Hp diesel
, which means that not only are you over powered, but you are going to have some carbon build up problems with the diesel.
My suggestion: Save the weight, use a smaller diesel, mount it as close to the current
center of gravity as you can, use a shaft and a prop, not an Inboard/outboard configuration, as that will change the center of gravity, the length of the water
line, and the angle the boat sits in the water
even under sail, etc.
Now, if your boat is designed for an outboard
, and you can keep the weight of the new motor
and out drive to around the weight of the designed outboard
, then you might be able to make it work.
Good luck, sounds likes a very interesting conversion. Keep us informed of how it comes out.