Calculating Maximum Draft with a boat

[Minchk]

I'm in the process or purchasing a 1999 Glastron SX170 with a 150. I'm trying to figure out what the draft would be without anyone in the boat and the maximum draft with a fully loaded boat. Any ideas? Thanks...

 

[backwater dawg]

Re: Calculating Maximum Draft with a boat

Duh--put it in the water empty and then have all your buddys jump in ( the boat--not the water) and take a look at the drive.

 

[Minchk]

Re: Calculating Maximum Draft with a boat

Backwater dawg.....Ok....I wasn't clear with my last post. I don't own the boat yet, but I'm curious what the draft might be with the heavier motor. To be honest, I just need to make sure I'm not limiting my options when I purchase this boat. It's a great boat, but if I need three feet of water below the boat, I won't be able to fish a lake that's two minutes from my house. I'd rather purchase a different boat then. I know there's a formula that's used to calculate max draft. I just don't know what it is. I owned a fishing boat before, so draft meant nothing to me.

 

[nlain]

Re: Calculating Maximum Draft with a boat

This is what the new ones show on the Glastron site

SSV170

• Draft Drive Unit Up: 15 1/2" (.39 m)
• Draft Drive Unit Down: 28 1/2" (.72 m) Max. Horsepower: 115 (86 kw)

SSV180

• Draft Drive Unit Up: 15 1/2" (.39 m)
• Draft Drive Unit Down: 28 1/2" (.72 m) Max. Horsepower: 150 (112 kw)

Not what you were asking for but should give you an idea.

 

[Mike Robinson]

Re: Calculating Maximum Draft with a boat

Trying to figure what the draft would be mathemetically is more trouble that it's worth IMHO.

I'm assuming the 150 you refer to is an outboard?

Being a used boat there should be signs of where the normal waterline is on the hull (dirt, oil etc.) If possible, lower the outboard, as this is going to be the deepest part of the boat and measure from the bottom of the outboard's skeg up to the waterline on the hull and add a couple of inches to err on the side of caution.

 

[themaniam1]

Re: Calculating Maximum Draft with a boat

Yup what Mike said ^. Check of a waterline. I there might even be a slight one on the outboard and just measure that to get the total draft.

 

[Minchk]

Re: Calculating Maximum Draft with a boat

Thanks for all the help. I'm going to view the boat this coming weekend. I'll look for discolorations on the motor and the rest of the boat. That should be a give away of how far it sits in the water. Thanks again.

 

[Triton II]

Re: Calculating Maximum Draft with a boat

Thanks for all the help. I'm going to view the boat this coming weekend. I'll look for discolorations on the motor and the rest of the boat. That should be a give away of how far it sits in the water. Thanks again.

Generally the waterline discolouration will indicate the draft when the boat is at anchor or on a mooring. The draft will vary from that when it's underway. You can cheat a bit by trimming up fairly high but three feet will always be a bit marginal in a boat of that size, weight and power - especially if you want to tow skiers or tubes.

 

[H20Rat]

Re: Calculating Maximum Draft with a boat

without the exact cad drawings of the hull and some fairly in depth calculus, there is no way to mathmatically calculate changes in draft. It isn't anywhere close to linear either.