I'm looking for some insight on the real differences between a BF75 and a B75 7.5hp twin.
I have a 1980'ish BF75-11014XX. There are no year marks on these motors. It starts and idles great, won't get up to speed, maybe 2000 rpm. Runs a little rich (plugs a little blackened). I"m at high altitude, and know I have to re-jet (has the stock #88 main jet in Keihin BD 25mm carb). I was looking for a 2nd carb to setup for high altitude (using a #82 to #86). This would let me just swap carbs for high altitude or sea level. Most of my sailing is at 6200 feet plus. BTW, it is a sailboat kicker, and I'm going to look into a lower pitched prop after I get the jetting just right. The alternator is usesless, since I can't get the RPMs up enough to get any more than about 11.5 or 12 volts.
I recently bought a carb off ebay from a B75 (NOT BF75), with 1000XXX serial. The ebay photo made the carb "look" very similar to mine. I missed the missing F in BF75 in the ebay ad. A B75 and BF75 are both twin 7.5hp 4-strokes.
The carbs are TOTALLY DIFFERENT. Mine is very simple, has only a main jet and emulsion tube, float, valve and needle, a choke plate and throttle plate. Mine mounts with the bore horizontal, into the intake manifold. The carb was spotlessly clean when I pulled it for inspection and to check the jet size. I cleaned it anyway.
The B75 ebay carb has the bore mounted vertically, has the float chamber sideways (the float is really weird being mounted sideways), and has 3 linkage plates (choke, throttle, and a third that operates a valve inside the float chamber). The bore is also smaller, say 22mm. Needless to say, useless for my BF75. I'll be re-selling it on ebay soon.
I have looked, but I can't find much detailed information on the history, years, differences between the "BF75" and the "B75". I verified the B75 carb mounting on the www.boats.net site parts diagrams. The intake manifold mounts the carb vertically on the B75.
Anyone know the real details about the differences? Are at least SOME of the parts interchangeable? Many of these are being parted on ebay now (both B75 and BF75, as well as BF100 10hp units). It would be nice to know what can be interchanged (like props, lower units, cowls, etc)
Finally, is there a chart for recommended main jet size reduction for high altitudes? Should I just buy the next 2 or 3 smaller jets and use the one that works the best?
Stu
Los Alamos, NM
I have a 1980'ish BF75-11014XX. There are no year marks on these motors. It starts and idles great, won't get up to speed, maybe 2000 rpm. Runs a little rich (plugs a little blackened). I"m at high altitude, and know I have to re-jet (has the stock #88 main jet in Keihin BD 25mm carb). I was looking for a 2nd carb to setup for high altitude (using a #82 to #86). This would let me just swap carbs for high altitude or sea level. Most of my sailing is at 6200 feet plus. BTW, it is a sailboat kicker, and I'm going to look into a lower pitched prop after I get the jetting just right. The alternator is usesless, since I can't get the RPMs up enough to get any more than about 11.5 or 12 volts.
I recently bought a carb off ebay from a B75 (NOT BF75), with 1000XXX serial. The ebay photo made the carb "look" very similar to mine. I missed the missing F in BF75 in the ebay ad. A B75 and BF75 are both twin 7.5hp 4-strokes.
The carbs are TOTALLY DIFFERENT. Mine is very simple, has only a main jet and emulsion tube, float, valve and needle, a choke plate and throttle plate. Mine mounts with the bore horizontal, into the intake manifold. The carb was spotlessly clean when I pulled it for inspection and to check the jet size. I cleaned it anyway.
The B75 ebay carb has the bore mounted vertically, has the float chamber sideways (the float is really weird being mounted sideways), and has 3 linkage plates (choke, throttle, and a third that operates a valve inside the float chamber). The bore is also smaller, say 22mm. Needless to say, useless for my BF75. I'll be re-selling it on ebay soon.
I have looked, but I can't find much detailed information on the history, years, differences between the "BF75" and the "B75". I verified the B75 carb mounting on the www.boats.net site parts diagrams. The intake manifold mounts the carb vertically on the B75.
Anyone know the real details about the differences? Are at least SOME of the parts interchangeable? Many of these are being parted on ebay now (both B75 and BF75, as well as BF100 10hp units). It would be nice to know what can be interchanged (like props, lower units, cowls, etc)
Finally, is there a chart for recommended main jet size reduction for high altitudes? Should I just buy the next 2 or 3 smaller jets and use the one that works the best?
Stu
Los Alamos, NM