Shaking at High RPM Running 1955 Evinrude Fleetwin Aquasonic 7.5HP

[fleetwin]

fleetwin wrote:

OK, so is the prop just spinning on the brass hub? Kind of hard to imagine how this could happen, maybe the prop was not machined/assembled properly…Or, perhaps the aluminum is cracked allow it to pull away from the brass hub…

OK, I’m confused….You have one prop labeled as the bad prop, but it looks like a good prop….The other prop is labeled good, and it looks like the one where the brass hub has separated from the aluminum propeller casting…

Does the engine vibrate using either of these propellers?

Strange how the props look the same on the shear pin end even though the brass hub appears to have moved out of the gearcase side. Perhaps these are two different vintages of props….
In any event, if you can turn the brass hub inside the aluminum casting, the prop is NG…

[Good-Fishing]

I got a spare parts motor and put in a new lower unit. Problem solved.Running great now. Just waiting on getting the engine tuned in.The white prop came from NOS , still have the box. the silver one came with the motor. I replaced it after the log strike because i was having acceleration problems.

[aquasonic]

“Perhaps these are two different vintages of props….”

I checked two 7.5 Fleetwin props that I have on hand. The 1954 and 1955 props match the dull aluminum one shown in this thread. The 1956 prop matches the white prop shown in this thread with the bronze hub showing reveal on the inside. Looks like a slight design change was made for 1956 and later.

[Good-Fishing]

Could be. It says its the same part number 277276, If that’s the case..2 different props for the same motor? Produced under the same part number. One for 54-55 and one for 56 and later.

[aquasonic]

PN 277276 prop was used on the 1954 and 1955 Fleetwins. PN 277650 prop was the upgrade used on 1956-1958 Fleetwins and AD models. It is a direct replacement for the earlier model.

[frankr]

I received a “gotcha” when I built up a 5.5 / 7.5 lower unit from parts salvaged from various motors. Everything went fine till I tried to put the prop on. It wouldn’t slide all the way on without banging up against an obstruction. Seems like the webbing inside the prop was the interference, but sorry I just don’t remember all the details.

[fleetwin]

Well, I do remember there was some sort of change made in 1956 in the rear seal hsg, not sure if the props changed also….
The good news here is that a replacement gearcase solved the issue, without doing a lot of investigation/replacement work on the original gearcase….
Perhaps the shock spring was actually broken allowing the two driveshaft halves to spin independently. The vibration may have just been a result of the spring pieces chattering around in there…
Perhaps the gear housing was actually bent/distorted, who knows…
Just be sure to mark this gearcase so you or someone else doesn’t accidentally use it in the future….
Although it is tempting to rip the darn thing apart to figure things out, just be sure to toss the parts away!

[Good-Fishing]

Lower drive shaft seals.

[fleetwin]

OK, well both of those upper driveshaft seal housings look like the lower driveshaft/shock unit was rubbing on them….Once the shock expands, the length of the driveshaft increases so it rubs on this housing. This is wear the binding occurs causing the engine to labor/stall, especially at higher speeds under more load…
So, the question is where did these two housings come from? Did you disassemble the original gearcase? If so, have you measured the length of the lower driveshaft/shock unit?

[Good-Fishing]

I picked up a 1954 complete parts motor that didnt run.The narrow one on the left came from the 54 lower unit currently on the motor.I just switched the lower unit and newer some parts over.I just I haven’t taken the gear case apart yet to inspect it.Just filled it with oil etc. It seemed in better shape. The other wider one on the right came from the 55 and it had more visible damage .I snapped the other shaft from the 55 trying to squeeze it back. So i deceived to leave the the other one alone until I open up the throttle and see if it causes any issues.

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