Mercruiser Alpha 1 Gen 1 Stern Drive Repairs Part 11: How to Upgrade The Shift Interrupt Switch

[@ProWrenching]

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[@dlp4183]

Thanks for the video! It took me a few days to find something like this, I wish this was one of the top results when searching ‘shift interrupter switch’

[@staceybarnes9582]

Thanks for the video and the part number, did this to my 1995 Maxum over the weekend,

[@ProWrenching]

Awesome! Thank you.

[@joedirt9600]

Make sure you check the shifter link adjustment, my 1988 Sea Ray Sundance was stalling constantly. I checked the shift linkage and it was out of adjustment.

[@HolyFix]

Bro thanks for making the video. since I bought my boat I can’t get the shift interrupter to work. I even changed and adjusted the lower shift cable. It barely moves at all, never leaves the valley. The switch itself tested out ok

[@CarlPrudeJr3]

Thanks for posting. I was thinking about making the same upgrade on my 2.5 Alpha 1 Gen 1.

[@ProWrenching]

Awesome! It worked great on my boat. I'm glad I did it.

[@gherickb8181]

As always brother you are the best !!!!!

[@ProWrenching]

Thanks, man! I appreciate that.

[@gherickb8181]

@@ProWrenching I still having problem whit the trim motor hose want charge me a LOOOOT they say , the engine have to come out !!

[@ProWrenching]

@@gherickb8181 oh no, sounds like a big job. I hope you can get back on the water soon.

[@mikew5432]

i have a 5.7 ltr with a hei distributor which i've assumed was original to boat,when i bought it nothing was hooked up, after lot of work and money runs great, but i don't know how to hook up the cutout switch with this hei distributor, i've seen companies selling these but i can't find anything bout the wiring of them to the cutout?

[@ProWrenching]

I would recommend contacting the Mercruiser customer assistance. Their phone # is 920-929-5040. They should be able to help you with the correct setup for your engine. I’ve called them before on other issues and they’ve been very helpful.

[@BobBob-eh5sb]

Late going to this video, but I was just looking for interrupter switches and saw that the old style is no longer available. I saw this new style for around $20. But the new plate is around $175. Saw a couple of the old ones on eBay for $90 to $100. I think like someone else posted, if it’s intermittent, check for adjustment and maybe a lose wire connection before spending a couple hundred bucks.

[@mellow-2]

Is it necessary to replace the gimbal fiber washers-I didn’t see them during removal.

[@ProWrenching]

You might check to see if they're possibly stuck to the sides of the gimbal. If not, I would get some new ones and install them.

[@paulplantinga2865]

Thanks for the video. My 1988 Sea Ray has twin 260 HP Mercruisers. They are intermittently stalling when shifting into reverse. I see the OEM switch lever as a big liability. I'm probably going to order 1 kit to see if it fixing that engine, then will do the other if the results are good. Does the kit have good instructions, including cable adjustment directions?

[@ProWrenching]

Yes- the kit does come with good installation instructions. I don’t remember if it has the cable adjustments . The procedure is the same as the original shift plate.

[@wikid4948]

Where did you get the extra long stud for the shift assist? Mine didn't come with one. The stock one is too short.

[@ProWrenching]

Mine came installed in the shift plate.

[@skidooextreme2233]

Have the same issue. Plate is moving is moving going into reverse but not forward and hitting the switch It is technically only to shift interrupt coming out of forward or reverse into netural. Everyone on the board tells me to replace the shift cable since it might be binding. I don't fully believe it yet since I had the cable apart and lubed it well upon reassembly. No resistance moving it by hand. Maybe I have a similar issue.

[@ProWrenching]

You might try seeing if the switch works while running the engine by pushing down on the shift interrupt switch and seeing if the engine dies. If the engine doesn't cut out or die when the switch is engaged, you know the switch is defective. It could also be a good idea to check and adjust the shift cables to make sure they're set correctly.

[@skidooextreme2233]

@@ProWrenching switch works perfectly. Adjusted correctly. Something is just binding it a little bit going into reverse and forcing the switch to activate

[@ProWrenching]

@@skidooextreme2233 the cable adjustment can be tricky. There’s also a slot on the front attachment point for the shift cable that will move up or down. It helps determine the reverse shift engagement. Sometimes there could be too much slack in the shift cable. When shifted into forward gear & with someone holding the propeller, the cable shouldnt have more than 9/16” slack.

[@moabbas5525]

Thank you so much I have mercruiser alpha 1 gen 2 . My issue is that when I put boat in forward the roller switch stays engaged and doesn’t go back to the “neutral position “ or the “valley” which then shuts off the engine . I can run it when I disconnect the switch without issues but obviously that’s going on cause damage . The switch is functioning properly but the issue like I mentioned the “V” shaped part stays in the forward or backwards position and keeps the roller pressed which then press on the switch, my understanding is that the roller should go back to the valley position “neutral “ and releasing the switch which keeps the engine running … iv tried to adjust the cables but still no luck not sure what to do

[@Realitygetreal]

I think you better double check that, this is a normally open switch when you shift it goes to the valley and beyond, when you pull back to neutral just before neutral it should be in the valley and open the connection temporarily cutting off the spark relieving the pressure on the gear box, if its in the valley at neutral you have something NOT in the right place.

[@moabbas5525]

Yeah I couldn’t figure it out . I’m wondering if I could add a shut off switch on the boat throttle control (lever)

[@fizzybillylah3816]

Do you know if it required for the lower unit to be lowered all the way down? It doesn’t seem like it should matter since the adjustment end is locked in place. Thoughts???

[@ProWrenching]

Yes- it needs to be all the way down. It’s harder to shift into reverse when the lower unit is in the up position

[@glenngray1201]

It should be down anyways not stored up except when moving on the trailer 😊

[@investedtolife7319]

Hi, this is a very informative video. Thank you so much. May i ask a question regarding to the issue with my boat. I can drive fast in the water but when i slow down to the point of going under 1000 rpm, the forward gear anymore will not re-engage. I can shift to reverse and will move. The current solution i have is to re-start the engine and it will work perfectly again, until i go under 1000rpm. Any advise, please.

[@ProWrenching]

I have not had that exact issue before. I would check all the cable adjustments and make sure that the prop will engage correctly after adjustment and also check the cable for too much slack. It may need replaced if it has too much.

[@leeh6816]

Great video. I’ve got the same shift plate on my 1999 mercruiser and find it stiff especially going from reverse into neutral. Did the new plate make it easier to shift for you?

[@ProWrenching]

@@leeh6816 thanks! Yes- I did notice it being a little bit easier to shift. I believe it is that shift assist mechanism that helps.

[@leeh6816]

Great thanks 👍

[@user-rr8dn5yl7d]

I'm installing the same kit on the same motor so I was excited to find your video. Unfortunately the information i was looking for is missing. The instructions don't include anything about wiring. The wires are color coded on the motor, but on the upgrade kit they're both black. So there's no way to tell which is positive and negative. The instructions say to connect the wires of the upgrade switch to the appropriate wires on the motor. But there's no way to tell which wire goes where. I was hoping you would help with that but you didn't cover it at all. Maybe they're interchangeable? But I hate to guess at something like that. It would have been helpful if you would've covered that.

[@ProWrenching]

@@user-rr8dn5yl7d it’s an open close switch. It doesn’t matter as long as it’s connected to the same two wires as the other switch, it will work

[@jasonbruno1065]

Thanks Pro Wrenching for posting this. I have been struggling with my shifting since I have gotten the boat. Replaced shift cables and adjusted several times only to have the same issue. Finally decided to pruchase the new shift plate kit as I have been constantly trying to straighten my inturuptor switch. I am hoping you may have some insight as to how to install this on the transom as I have the original is mounted on aluminum rocker. Instruction say to move to the transom or engine stringer. One last question: in the instructions it says to not change cable adjustments. Is there a reason why you rotated that cylinder four times? Curious if I should do that or leave as is. Appreciate your feed back 🙏

[@ProWrenching]

I rotated the barrel four times as part of the shift cable adjustment. I was readjusting the shift cable because it may have gotten out of adjustment while transferring it to the new shift plate. On my boat the new shift plate is installed in the same location as the old one. Unfortunately I don’t have any insight on moving the shift plate, as mine was bolted in the factory location. Thank you for watching!

[@josepeixoto3384]

You really know your stuff,thanks for the video,very helpfull to refresh things up,long time no do; Just finishing changing from a 3.0 to a Iveco 2.5Td intercooled ,about 150 horses; turns out to be a waste of time now,never knew diesel here would go up so much; i'm in Portugal (-that's in Europe, bottom left lol ) and doing the adjustment of the cables tomorrow; I don't have the shifter assist cylinder,is that just one spring inside? just one way push spring? i could easily make one, what is it for, i have the old plate with the roller micro-switch already properly wired,working fine by hand,maybe i don't need it ?

[@ProWrenching]

Thank you! That sounds like a cool project. It’ll be worth it when the price of diesel goes down eventually. If you have the old plate with the roller switch that is working fine, then you don’t need the shift assist. Yep- it’s just a one-way spring that helps with the shifting process. Glad my video was helpful!

[@yarmoth6]

Great video thank you! I’m thinking about doing this, I have a 87 SeaRay with a MerCruiser 4.3. Everything was working fine and then suddenly if I put it in reverse the engine dies, and if I put it in forward throttle it sounds like it’s flooded or bottoms out… If I slightly past the throttle I can at least trot around without having to get towed and now that I think about it I think it always goes forward even in neutral. I’ve heard any ideas but a lot of people seem to be pointing at this shift interrupt or switch or the cables… I am new to this so I’m trying to figure out which cables how to change the cables or if it’s just needs to have the switch or cables adjusted? Any advice?, Thanks again!

[@ProWrenching]

Thanks for watching! If it’s moving forward even in neutral, it sounds like your shift cables are out of adjustment. I would start by adjusting the shift cables so they are correct. You want to make sure all the shift cables are correct before you think about replacing the switch. Sounds like the switch might be working, just out of adjustment.

[@tomm2271]

Hello from Ohio. 1986 Imperial 20' cuddy. V-8 like yours. Was having reverse engaging problems from last year. I thought I would replace the cut out switch due to age. I found a guy that had a brand new OEM roller cutout switch. Installed no problem. I spent ALL day playing around with cable adjustments. It doesn't seem like the shift cutout switch LEVER is activating properly. It wont move and "snap" like it use to, thus not properly operating the cutout switch . Sometime it doesn't even move, I cant figure it out. I did the 6 inch measurement and spun barrels in every direction....no go. Do you think a new kit/plate would resolve? Approx how much is it? I already threw away $100 on the OEM switch...lol

[@ProWrenching]

The cut out switch is tricky and it’s hard to tell if it’s functioning correctly unless you have the boat out on the water. If it’s not working right it will kind of hang in gear when you’re trying to shift from one gear to another. It works by cutting out the motor just for a tiny second to take a load off the lower unit to allow it to come out of gear and into the next. If your issue is not actually being able to get the boat to shift into reverse when it is out of the water just to engage the propeller, you might try adjusting the attachment to the shift cable. There is a slot- you can move the attachment going up in the slot to help engage in reverse. I hope this helps. I paid around $189 for the shift plate.

[@tomm2271]

@@ProWrenching thank you!.. We put muffs on and fired it up. Its going into F/N/R, we just don't hear the engine cutting out for a split second as it should. I'm afraid were going to damage gears. Why would putting in the water make the shift lever move? Ive read that also.. Something about back pressure?

[@ProWrenching]

@@tomm2271 The boat will shift differently on the water due to the pressure on the propeller. You will know if the switch is not working because it will be hanging in gear when you’re trying to shift. The motor will cut out quickly- you probably won’t even hear that is happening. The Alpha 1 Gen 1’s do make kind of a clunk noise when they shift.

[@robertosb2889]

Muy buena explicación, perfecto,gracias.

[@ProWrenching]

Gracias

[@donaldtryon8292]

Replace grease zerk on mercury cru