Engine size for an 18 foot flat bottom aluminum boat

dissturbbed

Seaman Apprentice
Joined
Jul 9, 2014
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30
Just bought a 18 foot aluminum boat wide bottom, needs engine just dont know what size to get..What would be a good size?
 

GA_Boater

Honorary Moderator Emeritus
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May 24, 2011
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49,038
Is there a yellow sticker/plate that has the max HP?
 

robert graham

Admiral
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Apr 16, 2009
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My boat is an Express 1870, aluminum, all welded, a very slight V deadrise of 6 degrees at the transom....mostly flat bottom. The boat/motor package came with a 90 HP Yamaha....it's always been for me a bit more power than I generally use...will snap up on plane quickly and plenty of speed.....but honestly I believe a 70 HP motor would be more than adequate for my boat. Of course it would all depend on how far/how fast you're wanting to go....Another factor is that flat bottom skiff type boats aren't all that good for high speed, since they can tend to porpoise if trimmed up for speed.....good luck!
 

minuteman62-64

Lieutenant
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Apr 12, 2011
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1,350
I have a 1982 15'6" Bayrunner, V in bow, flat at transom. 30 HP Mariner does fine - goes as fast as I want to go, particularly in chop. Bayrunner also made a 1980's 18'6" model, same hull configuration - standard equipment was (and still is - lot of them still running around San Diego area) a 40 HP.Mariner.
 

robert graham

Admiral
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Apr 16, 2009
Messages
6,908
One other factor is the manufacturer/construction of the boat you purchased....for instance, Sea Ark aluminum boats are made from .125 inch aluminum while my Xpress aluminum boat is made from .100 inch aluminum.....so different manufacturers make heavier or lighter weight boats....I've seen "industrial grade" aluminum work boats made of welded .250 inch aluminum plate....so check your weight/construction before deciding on outboard HP...
 
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