Mercruiser Shift Interrupter Switch

[partychefman]

Hi all.
I have an 18 ft Carribean Baron half cab with a V8 Windsor 302 engine / alpha one stern drive. I bought this boat a few months back and it has been having issues since, I seemed to have had most of the issues nutted out.

At the moment, when underload, going from reverse to neutral / forward and vice versa the engine cuts out. I can restart the engine straightaway (most of the time) but this is an issue especially coming into / out of the boat ramp. I have done a fair bit of research (thanks to these forums) and pin pointed the problem to my shift interrupter switch. (Located near the transom, attached to the shift cable etc.)

I have checked the adjustment of the shift cables and they are within specifications. I have seen a YouTube video and comparing that to the movement of mine, it appears this may be the problem. The video I have seen had the same switch but had a slightly different set up. I have attached some photos, they are the best I can upload on here.

This is my first boat so if I have been vague with any information that you need, let me know.

Thanks in advance, PCM

 

[Fishermark]

Re: Mercruiser Shift Interrupter Switch

You have correctly identified the reason the engine dies. The switch is killing the ignition. But the reason it is killing the ignition is your shift cable is binding. The engine needs to "stumble" in order for the outdrive to come out of gear. That's what the switch does. If it takes too much effort to come out of gear, then the switch stays engaged longer and causes the engine to die. 99% of the time, your cable simply needs to be replaced. It might only need adjustment... but I would guess it is time for a new cable.

Oh yeah, welcome aboard!

 

[dubs283]

Re: Mercruiser Shift Interrupter Switch

like fishermark says...time for a new lower shift cable

great opportunity to pull the drive and inspect the bellows/transom assy components

 

[partychefman]

Re: Mercruiser Shift Interrupter Switch

Thanks for the reply. I am slightly relieved it is not the switch after seeing how much trouble it is to get a replacement.

I will take to opportunity to check out the bellows etc. I will need to replace my trim limit sender anyway.

Are these things fairly universal or do I need to remove the existing cable and get the exact same length?

 

[Fishermark]

Re: Mercruiser Shift Interrupter Switch

You may have the older style of shift cable - the old style threads from the forward side of the bellhousing. The newer style threads from the aft side. Not a big deal, but the only one available is the new style. You will need to buy a tap and complete the threads so you can screw the cable in on the aft side.

While you are at it, go ahead and buy the genuine Mercruiser (Quicksilver) shift cable. I have used both the aftermarket and OEM styles, and the OEM cable is quite a bit better.

 

[84imperial]

i also have a question on this topic. i have a 84 imperial with either an mr or alpha 1 outdrive. im in the middle of replacing the shift cable. the one i removed threaded in from the outdrive side, and when i went to install the new one it seems to big, or the same size as the threaded whole in the bell housing. im not sure if that is a threaded insert in there or what, but the cable fitting just seems to big to thread in there, but it should be the same cable . i think theres only 1 you can get isnt there??

 

[84imperial]

i also have a question on this topic. i have a 84 imperial with either an mr or alpha 1 outdrive. im in the middle of replacing the shift cable. the one i removed threaded in from the outdrive side, and when i went to install the new one it seems to big, or the same size as the threaded whole in the bell housing. im not sure if that is a threaded insert in there or what, but the cable fitting just seems to big to thread in there, but it should be the same cable . i think theres only 1 you can get isnt there??

 

[Bt Doctur]

Sounds like it was broken and you removed one half of it, the threaded section that broke off is still in the housing. All the cable threaded ends are all the same for Alpha drives, 1/4 x 18 NPST. post some pics of the old cable end.use photobucket.com

 

[84imperial]

could be i suppose. when i went to remove it the brass part broke. i had to heat it a bit and use an extracter to get the rest of the brass fitting part out. that had threads on it, so i figured i got it all out. and the threads i was seeing in the bell housing was what the cable threaded into. it looks like a threaded insert though. ill try and get some pics up soon. im about 20 min. away from were i keep the boat.

 

[Bt Doctur]

If brass is in there, the best thing to do it get the correct drill bit to tap 1/4 x 28 and the special tap and retap it straight.

 

[84imperial]

but when i removed my cable it looked like this so im pretty sure i got it all out.

 

[84imperial]

there is no brass in it, thats why im confused. i dunno maybe i just have to run a tap through it and clean it out some. but the cable is defenitly bigger than the hole.