Reply To: 1964 Evinrude Speeditwin 28, @ cottage, no pwr

[Don]

OK, so the problems began when the tube almost stopped the boat.

First:  I really don’t think there is anything wrong with the gearcase/lower unit, so please don’t take it off and rip it apart.  With the engine in gear, you will only be able to rock the propeller back and forth just a bit, which is normal.  The propeller should spin freely when in neutral though.  You inspected the shear pin and it is OK.

Tell us more about the running symptoms now.  You mention the engine has no power at WOT, does it idle properly?  Does the engine rev up but not deliver any thrust at WOT, or does it not not even “wind up” when the throttle is pushed all the way up in gear?

It almost seems like the engine is running on only one cylinder, but idle performance would be affected as well if this was the case.  I’m just thinking there might be some sort of connection between the boat being almost stopped in its tracks by the tube and the loss of WOT power.  Perhaps the linkage got messed up when you were wrestling with the throttle during the event.

The throttle linkage on this engine is a little complicated, there are a few things there that could be causing issues.  First, there is the “neutral lock out/limit” linkage that prevents you from over revving the engine in neutral.  There is a vertical rod that runs up from the shift lever to underneath the mag plate.  When in neutral, the vertical arm stops the mag plate from advancing fully, the vertical arm swings out of the way when in forward.  So, if this linkage is messed up, it might be limiting timing advance at higher throttle settings, usually the throttle linkage won’t advance past this setting in neutral, but I suppose it might be possible to advance the throttle control/linkage past this point.

Next, there is a complicated little throttle linkage called the “economizer linkage”, this allows full WOT timing before the carburetor opens fully.  There is a little brass barrel/screw on the left side of the engine mounted to a small diameter horizontal round rod which links the mag plate to the carburetor linkage at higher throttle settings.  So, if the screw on that brass barrel has loosened up allowing the barrel to slide back, your carburetor won’t be opening up fully limiting WOT power.

Next, the is a vacuum switch located on the left hand side of the engine which keeps the engine from over revving when the throttle is cut back quickly by cutting out spark to one cylinder.  The vacuum switch is connected to one crankcase to sense high vacuum  which would occur if the engine is over revving with the throttle closed.  When the switch closes at high vacuum, it grounds out one set of points killing spark to that cylinder.   Once RPM comes down and vacuum decrease, the switch opens allowing that cylinder to spark again.

Finally, perhaps your control box/cables got messed up so the engine throttle linkage is not being advanced fully.

So, your best tool now is a good visual check of the linkages to make sure everything is working properly.  In other words, shift the engine into forward gear (you may have to rotate the prop slightly to get the gear/dog lugs to align allowing full forward engagement).  Now, have an assistant hold the engines throttle linkage in the WOT position.  Is the carburetor opening fully?  Is the mag plate moving to its WOT stop?   You have already pulled the engine back off the boat?  If not, I would simply use the remote control to set the engine to WOT in gear.  Perhaps the cables/box is messed up preventing the engine linkage from advancing fully.