77 merc shift interupter switch.

[SeattleSeaRay]

Just installed rebuilt pre alpha through transom assembley. Aligned motor, plugged everything back in and fired her back up! Unfortunately, somewhere along the way a spade terminal broke off my shift interupter switch. Looks like a small, low cost electrical component right? Wrong! Apparently no longer available except through specialty dealers in antique boat parts, my local guy wants $250 or found used as low as $20 online. Then I read Mercruiser makes a complete new plate Assy retro kit with new style switch for approx $150 any recommendationsuggestions of which way to go?


1977 Searay SRV 220 351w Ford Mercruiser / MC-1 Outdrive...

 

[SeattleSeaRay]

I found this excellent write up..


The purpose of the switch is to kill the engine for a fraction of a second to release the gears. Normally adjustment of the shift assist switich will be required if the engine kills when shifted into gear. The mere fact that it is killing the engine proves that the switch is good, it is working at the wrong time(going in gear).

If the boat has no neutral, when you try to shift to neutral it fights you and passes from fwd to rev or rev to fwd, then you have a problem of a sticking shift cable or a sticking shift arm and roller on the upper shift shaft. This adjustment is addressed in part two of this page below.

The gears in the outdrive are undercut so once together they stick together if there is a prop load(in the water). When the forward cable tries to move the lower shift cable it fights the action and is felt as a resistance on the shift handle. Pressure on the lower shift cable shifts the arm that trips the easy shift switch, thus the engine starts to die. One second later during the lapse in h.p. the gears let go, then the switch resets and the engine regains power. The whole process takes only a second and the engine recovers with only a hesitation, which you hear (whooomp)

 

[Fed]

That's a terrible write up Ray you will find a much better one in the stickies at the top of the Mercruiser Forum.

Without searching it out for you I'm sure you will find the correct replacement switch very cheaply, I'd expect to pay no more than $20-$30 for one.