79BFN

Glad you get her running right! When are us Carolina boys gonna hook up? Kids start back to school Thursday and fall is right on it's tails.

when you inspected the plugs did you only use the boat at the "problematic" rpm range?

Eric, maybe it's too lean?

The strut is your fixed point. Disconnect the coupler and loosen the log boot so the coupler end moves freely. Then prop the coupler end of the shaft and adjust that until the shaft is centered in the cutlass bearing front and back. Then align the engine to that.

eric lavine wrote: Greg did we miss the obvious......you, if anyone should know

It's tough to say from here...just tried your cell.

OK, the plugs don't look too bad, but what do they look like? Clean, brown, black? Does 1 or 2 look different than the majority?

To me, an engine vibe feels 'heavier' than a drive vibration if that helps. Did you start at the strut when you did the alignment?

I've been following this thread for some time now and let me tell you, you have done a great job on restoring this boat! I'm slowly grinding out my stringers. I know my boat will never look as good as yours,but,I use your project as a reference to my 72 southwind. I'm new to inboards and I'm no trans expert either. I've read that you had water in your transmission. Seems to me water in the trans could kill a bearing like main bearings in an engine with water in the oil. The way your log was wallered out seems like the tailshaft bearing(if that is what it is called in a marine trans) had a lot of stress on it for some time. If it was a truck I'd say it sounds like either a u-joint, a pinion bearing, or a tailshaft bearing. Seems like you've replaced or repaired every part of the rotating assemblies fore and aft of the trans. Just an outsiders opinion. Happy hunting, can't wait to hear that 2000 rpm's are smooth as the work you've put in to that beauty.
Scott

Greg, plugs really don't look bad. I'm guessing I just haven't run it long enough cause they still look new.

Well, whether it solves the problem or not, I'm going to replace the wire going to the coil from the ign. switch. The meter only shows 6.5 volts on the + side of the coil........must be a "resistor wire". I thought that most everything went to "ballast resistors" in the mid 70's.

New coupler with new shaft and I put it in the lathe together before installing. Runout of .001. The coupler on the transmission I checked with a dial indicator and see .002. I am convinced that it is not comming from the shaft or the prop. I believe that the old shaft and coupler being out .020 was not even being felt now that I've put the new shaft and prop on. That new prop was worth about 4mph on the top end and it was worth the money but it hasn't solved my problem.

I'll be checking them out good. With my luck, anything I did out on the dock would be a sure way for me to drop something expensive in the lake.

I put new plugs and wires in on the weekend of the 4th of July. After the runs I put on her this wknd., I probably should check them and will one night this week. If I have something goofy going on here, wouldn't it also show up at WOT?

New shaft in and eventually put the new prop on. Still have the vibration at low rpm. It almost feels like it's in the motor and is amplified under a load or in gear. Could the motor mounts be worn out? It's a slight vibration, and it's all under about 2200 rpm. Could it come from the transmission? There is backlash in the transmission. (Feels just like the backlash in a rearend housing, however, more.) If I had to guess, I would say it feels like about .020. I'm running out of ideas.

Minimizing strut to prop clearance will put less stress on the shaft and cutless bearing (possibly reducing wear and/or vibration). It also has a positive effect on the boat's performance... namely it will raise the nose ever so slightly at speed.

The original 13x15 Federal doesnt clear the hull by much- Id say less we had less than 1/2" on ours. The keel was pretty beat up aft of the strut because of it- the rudder port and surrounding glass took a pretty good beating. Luckily, the aft rake on the blades of more modern props like the Acmes improve hull clearance, even with the shorter shaft. We had 1.5" cut off, so we're at 39.5" now. Prop to hull clearance is around 3/4" with a 13" diameter prop.

Kirk, while youre ordering a new shaft, dial in the length. You want to shoot for about 1/2" clearance between the prop hub and strut. We had quite a bit more than that on our BFN, and had the shaft cut down to correct it.

Kirk,
Before you go to the trouble and expence of a shaft replacement, I suggest checking it. It can be done in the boat. Using a dial indicator is best. It's mentioned in the alignment video that's in the "new" section of the forums.

If it is out (.003" max), the the ARE double taper shaft is the way to go.

Good to hear it. Hope its all smooth sailing from here!