Page 1 of 1
1980 F26 Flybridge
Posted: Fri Aug 12, 2011 12:08 pm
by JimmyM
Hi All
Still working on our 1980 F26 flybridge project. Comming along slow, but lookin good. After sitting a few years we are running old fuel out of her mixed with fresh. What should our top speed and RPM be ? We did a short haul cleaned and painted bottom and installed new 13in prop.
She has a 2002 mercruiser and velvet drive.
Thanks in advance
Posted: Fri Aug 12, 2011 2:33 pm
by ready123
Need more info....
Max rpm should almost = spec WOT for engine.
Then you can calculate theoretical speed using gear ratio of velvet drive and the pitch of prop and allow slip losses of 8-10%.
You need to supply the specs of your boat.... it is unlikely to be the same as another.
Engine model gives WOT rpm
Velvet ratio & prop pitch combined with above can answer the speed.
So how about supplying some spec data?
Posted: Fri Aug 12, 2011 8:49 pm
by MattSC
Hi Jimmy,
Glad to hear that your project is coming along, you should post some photos.
Ready is correct in needing more info to help you out. Is it a rebuilt original Mercruiser, or a newer fuel injected model? That will make a difference in what rpm you should be able to reach. For example my original Chrysler 318 needed to turn 4000 rpm at WOT, my current 5.7 crusader, an "02" model which is fuel injected needs to turn between 4800 and 5200 rpm at WOT.
As far as your velvet drive, it would be a pretty good bet that it is a 1:1 ratio. Your prop shaft should be 1". As for props, mine originally shipped with a 14x10 cupped prop. I can cruise at 2900-3000rpm between 15.5 - 17.5kts depending on conditions. I can reach a top speed a little over 31kts. With the original engine my top speed was right around 25.
Good luck and enjoy your boat!