DonziJon
01-06-2007, 06:33 PM
Recent thread about "Small Mods" devolved into a discussion about a 78mph 18 Classic.
RedDog said he had an 1990 18 Classic with a 454, 420 HP motor that would only do 71mph. I have a real problem with that. How can that be?
Just a point: My Minx will do 60 on the GPS with 260 HP at the flywheel. 63 mph on the pitot tube speedo that came with the boat. I think Mercruiser changed the HP rating around 1992..to.. HP AT The Prop. The outdrive uses up about 30 HP. So my Minx is about 230 HP at the prop. Probably all Irrelivent.
OK: How is it possable that RedDogs 18 ONLY does 71?? 420hp..less 30 hp loss at the OD (it's a Pre 1992) comes in at 390 HP at the prop. I think that boat should be a LOT faster. Does the weight of the 454 in the back of an 18 make a difference? Does the boat become "squirely" with the extra weight aft, and HP?
Geeos boat is in the back of my mind which confuses me. That boat does around a 100mph, does it not??? I understand that boat has an "Arnesen" drive. Just wondering. John
RedDog said he had an 1990 18 Classic with a 454, 420 HP motor that would only do 71mph. I have a real problem with that. How can that be?
Just a point: My Minx will do 60 on the GPS with 260 HP at the flywheel. 63 mph on the pitot tube speedo that came with the boat. I think Mercruiser changed the HP rating around 1992..to.. HP AT The Prop. The outdrive uses up about 30 HP. So my Minx is about 230 HP at the prop. Probably all Irrelivent.
OK: How is it possable that RedDogs 18 ONLY does 71?? 420hp..less 30 hp loss at the OD (it's a Pre 1992) comes in at 390 HP at the prop. I think that boat should be a LOT faster. Does the weight of the 454 in the back of an 18 make a difference? Does the boat become "squirely" with the extra weight aft, and HP?
Geeos boat is in the back of my mind which confuses me. That boat does around a 100mph, does it not??? I understand that boat has an "Arnesen" drive. Just wondering. John