re power

[cjm1300]

Hi guys I have a 20 sf I just got handed to me. I was wondering if the transome can hold a mercury 250 xs optimax. The year is a 84 and the transom is soiled. Also if any one can tell me the fuel tank size I think its 70 gals. Thanks

[Yz2009]

WIll the transom hold it? Probably, but i wouldn't put that much weight on the back of it. Try and stay closer to 400lbs or less.

[Bushwacker]

Carl Moesly designed the 20' hull for the I-6 Merc, which weighed less than 300 lbs! Think about it. The further you go above that, the more you screw up the CG, which means the boat won't ride as well as designed, and your min planning speed will increase, which is a big deal if you plan to run offshore in rough seas. Also keep in mind that the SeaCraft hull is lighter, narrower and much more efficient than the average modern deep V, which means it doesn't NEED as much power as most modern 20' boats. The 20' hull will start to go airborne in seas over 3' at speeds over 20 kts, so unless you're into racing on flat water, a 150 is more than enough power for a 20 if you run offshore very much!

[cjm1300]

Thanks guys I can just get this motor cheap. I am going to put transome knees in it just to be sure. Also I don't go off shore to much maybe just around tbd inlet. The xs weights is 504.

[Blue_Heron]

An '84 is a Seacraft Industries hull. They stretched it 8" longer than the Potter SF and it might handle the weight better as a result. That being said, I agree with the other posts. I've got a 200 Merc on my Seacraft Industries 20SF and it's more than enough motor. If you're going to fish offshore, a 150 will probably deliver more torque at the speeds you'll be running. On the other hand, if you just want something that will haul a$$ on flat water, the 250 is the ticket.
Dave

[FishStretcher]

I got my 1975 master angler hull airborne today at about 17 knots in 3-4 foot seas. With a 100 hp Yamaha 4 stroke pushing and the kicker hanging back there. A 366 lb main motor and a 58 lb kicker.

I have a forward mounted tank and batteries. To put power in perspective. I pull about 35 MPH on the flat and I am still tuning for trim.

Carl Moesly designed the 20' hull for the I-6 Merc, which weighed less than 300 lbs! Think about it. The further you go above that, the more you screw up the CG, which means the boat won't ride as well as designed, and your min planning speed will increase, which is a big deal if you plan to run offshore in rough seas. Also keep in mind that the SeaCraft hull is lighter, narrower and much more efficient than the average modern deep V, which means it doesn't NEED as much power as most modern 20' boats. The 20' hull will start to go airborne in seas over 3' at speeds over 20 kts, so unless you're into racing on flat water, a 150 is more than enough power for a 20 if you run offshore very much!

[eggsuckindog]

Thanks guys I can just get this motor cheap. I am going to put transome knees in it just to be sure. Also I don't go off shore to much maybe just around tbd inlet. The xs weights is 504.

My 200 2.5 rolls in at 405/416 and thats a stretch - honest

T Top and both batteries up under the front console seat, all adding weight forward

[pianewman]

Okay, now it's beginning to make sense to me. I thought I had been cured of the "Seacraft" addiction since 1989, when my dad sold his 1974 Tsunami. We wondered at the time why there were so many Seacraft owners that were adding trimtabs, as we found the concept unnecessary.
Fast forward to 2010. My dad, at 87, has a relapse, buys a 1973 20' CC, with a heavy Johnson, repowers with a 2008 Merc 150 (I think 450lbs. +), and we wonder why the aft of the boat sits so low in the water!
Thanks for the clarification. Now I know why the move toward trimtabs to assist getting on plane, etc.
Are the fins that attach to the cavitation plate of any value? Sure would be a lot less fuss than installing trimtabs.

Carl Moesly designed the 20' hull for the I-6 Merc, which weighed less than 300 lbs! Think about it. The further you go above that, the more you screw up the CG, which means the boat won't ride as well as designed, and your min planning speed will increase, which is a big deal if you plan to run offshore in rough seas. Also keep in mind that the SeaCraft hull is lighter, narrower and much more efficient than the average modern deep V, which means it doesn't NEED as much power as most modern 20' boats. The 20' hull will start to go airborne in seas over 3' at speeds over 20 kts, so unless you're into racing on flat water, a 150 is more than enough power for a 20 if you run offshore very much!

[Fr. Frank]

Okay, now it's beginning to make sense to me. ...
Thanks for the clarification. Now I know why the move toward trimtabs to assist getting on plane, etc.
Are the fins that attach to the cavitation plate of any value?

Yes, those fins help. Even more effective is the Hydro-Shield, which mounts to the skeg, so that it is always exerting influence on trim, whereas with the Davis Whale tail, or Stingray Hydrofoil, or Attwood Hydrolizer, they are all exerting minimal influence when on plane, and exert almost no influence when on plane and trimmed up beyond neutral trim angle.

The Hydro-Shield also very effectively protects your prop in shallow water.