repower
 

I am trying to finish the restoration of a 1976 20' SC and would like some imput on power. The boat will have no top. I am going to use a 55 gal belly tank and want to get the best range possible without compromising performance too much.The options I am considering at this point are Suzuki 4 strokes either the 140, 150 or 175. If anyone has any imput and some numbers to boot it would help a great deal.

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"55 gal belly tank" => a belly tank is not going to use the space efficently. Which 20 do you have? MA's can fit a 70 gallon tank.

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My '76 is not a MA. The 55 gal belly tank is a stock tank from West Marine. I would like to go larger but do no have any outlets for fabrication. The original tank was 48 gal.

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If you keep the Seacraft scuppers and original deck height the 20'SC is sensitive to motor weight. That said; 140 horsepower will give about 40 mph w-out a top, 150 probably 42 or 43 mph.

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Thanks for the numbers. I will keep the floor height the same but am looking at a small design change with the scuppers.

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MJ - what are the dimensions of that 55 gallon belly tank from west marine? I don't recall west selling any tank of that capacity which will fit into the 20ft seacraft hull.

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West Marine offers two 55 gal belly tanks. One is by Todd and the demensions are 51"L 25 1/2"W and 16"H. The other is an aluminum tank and it is 48 1/2"L 24"W and 9 1/2"H. Both tanks are listed on page 264 of the '06 catalog.

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I'm 99.9% sure that neither of those tanks will fit under the floor of the seacraft sf20 w/o raising the floor several inches or grinding down the center stringer.

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23 1/4" x 90 1/4" x 8 These are the dimensions of my 70 gallon tank in the stock 20 MA.

Do a search on the board for fuel tank Dimensions or maybe someone can post their SF dimensions.

This is hermco's tank on his SF 20.

http://www.hermco.net/pics/Myseacraft/msc12.jpg

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Thanks for the demensions on the 70 gal tank. I still have the floor out of my boat so if I can find someone to fabricate a tank for me I will use that one.

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The 47 gallon tank that came out of the MA was 23 1/4" x 60 1/4" x 8"

You might be limited by the size of the removeable floor hatch on the SF, so 70 gallons might not fit your boat without cutting the floor. I would highly recommend pulling the tank and measuring it, before you buy/order a new one. It's not worth making a $500 mistake.

If you are located anywhere near Florida . . . Marine Connection Liquidators has some nice fuel tanks for about $3/per gallon.

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Thanks for the info. I have the floor completely out of the boat so I can go with the 70 gal if I want. Do the guys in Florida ship?

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If you get a new four stroke fifty gallons is plenty. My 140 will go forever on a tank. Last year I used to get five two hour fishing trips out of about 23 gallons. I watched the hour meter and tried to fuel up at ten hours or so. This year I'm gonna watch the fuel consupmtion real close. I moved my batteries from the rear and put them up under the console and it helped getting on plane a little and the boat sits correctly. I could not find a commercially made tank that was even close to the stock tank. The hieght is kinda short but you could have one made longer because there is some more room in there if you measure. A custom made tank is the only way to fly.

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Thanks for the info on the 140. What type speed can you run?

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Mine is set a little low but I still get 34-36knts(depending on which way the tide is rolling) out of it, most days I'm lucky if I can cruise at 25knts before the sea conditions slow you down. I have it propped right at 6200 RPM WOT with a 18 prop. I would look at the 175 Suzi but the 140 is heavy enough for me. Not sure what the 175 weighs, I know the 150 Yami is heavier than the 140, 420hrs on my Suzi 140 and love it.

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Jon,

Thanks for the numbers. The 140 sounds like it will move the boat just fine. I will be using my boat more in back water and bays rather than off shore so i will investigate the 175 so that I might get a little more top end not having to worry quite as much about rough seas.

Thanks
MJ

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If gas was not a worry I would think that a carbed v-6 175hp Johnson would be a perfect match for this boat. Lots of torque light and haul A$$, but gas is a reality so I love my fourstroke. You get used to the hole shot not being the same and just drive it a little different. In a drag race from 20kts cruise my boat stomps my friends Yami 150 on a 20 Mako. He will get me from a dead stop but if were moving its a differnt story. The top end on the four strokes is where its at. The mechanics say "let it unwind" They just accelerate hard once you get them up. I run mine at cruise 4000-5000 depending on how fast I can run. Before I bought mine I talked to at least five people with the 140 and no one had anything bad to say at all about them. I have 421hrs on it in two and half seasons. The funny thing is it uses half of what my carbed 115 two stroke used. I'm not complaing about that at all beccuase I was happy with the 115's fuel economy. :D

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Jon, The 70 gal. fits good in the 20'.
http://img.photobucket.com/albums/v2...pandedging.jpg

Your right about the fuel. I'm really glad I don't have 2 to feed.
http://img.photobucket.com/albums/v2...t/withtabs.jpg

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Bobber - What are the dimensions of your 70 gallon tank? How high did you raise your floor?

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Big,
Can't remember the size of tank, had it custom made to fit between stringers. It starts at the back side of the CC and goes up to the casting platform. Pushed as much weight forward as possible for the larger motor.
For the deck, added 3/4 material to the top of the stringers as shown and for the deck used the same material as the bulkheads (composite). The floor is about an inch and a half higher then original. You can see the thickness of the composite in the new location for the bait well.
http://img.photobucket.com/albums/v2...sfordrains.jpg