Mercruiser 470 shift cable replacement and interupter switch operation.

[thermalfinder]

I just signed up for this site and I would appreciate any advice that can be given. It appears that the subject of shift interrupter switches and lower shift cable has been discussed quite a bit. I have a problem with my 1979 Mercruiser 470 dying when shifted into either gear, only when cold. after about a half hour of running it doesn't die anymore and runs perfectly, although the shifting does seem rather stiff and I have to ease it into gear. It is hard to do this sometimes with out "gunning" the engine. I suspect the lower shift cable is interfering with the shift interrupter switch. I have adjusted the cables but it still does it. I have a few questions about the operation of the shift interrupter switch and arm. I have tested the switch with an ohm meter and know that it is good.
#1-The arm that activates the rocker switch is spring loaded- when shifted into either forward or reverse should this arm center itself back up so the roller rocker is back in the valley of the arm when in gear? It seems to me that it should or the ignition system would be grounded constantly when in gear. Mine doesn't center back up. With the cable disconnected it does. This leads me to believe the cable is sticking holding the arm from returning to center.
#2- With an ohmmeter connected to the switch I have continuity at all times when shifted into reverse but no continuity in forward. I have bent the arm on the switch but I can't seem to bend it quite enough to make continuity in forward. I find it odd that, even with the cables disconnected and operating the lever with the y-spring on it by hand I still get no continuity in forward
#3- I am inclined to replace the shift cable regardless, but the one that I have found as a replacement is an "aft" design as opposed to a "fore" design. Evidently the "fore" design is obsolete. The supplier said that it should work fine but that I will need to retap/rethread a new hole. There are no directions with the kit, but they said that everyone that replaces their cables have to do this. Is anyone familiar with this? Do I need to drill a new hole or is there an existing hole that just needs to be threaded?
Any help on this would be greatly appreciated-
Kevin

 

[thumpar]

This shift interrupt should only be activated when coming OUT of gear. Watch the action of the shift plate while someone works the throttle. The threads on the old style don't have threads all the way through. You need a tap to cut the threads in the bellhousing all the way through the hole.

 

[Bondo]

This shift interrupt should only be activated when coming OUT of gear. Watch the action of the shift plate while someone works the throttle. The threads on the old style don't have threads all the way through. You need a tap to cut the threads in the bellhousing all the way through the hole.

Ayuh,..... 'n Only when the prop is in the water,.....

Alphas have to be shifted, Briskly, in, 'n outa gear,....

Replace yer Lower cable, 'n then adjust from there,....

Lotsa Great Info, 'n Vids in Don'S Adults Only section at the top of this forum,...

 

[thermalfinder]

Thanks guys- your responses are much appreciated. My shift plate moves and keeps the interrupter switch activated with the boat out of the water. I will replace the shift cable next week and let you know how it goes. The engine dies when cold- if I let it run for 15 minutes or so it runs great. I have the carb being rebuilt right now and have an electronic ignition conversion kit coming for it to get rid of the point system. The boat is really currently unsafe with the dying issue. Several times I have pulled away from the dock in a current and have been in a very bad predicament.

any more suggestions would be greatly appreciated!!!!

 

[nola mike]

#1-The arm that activates the rocker switch is spring loaded- when shifted into either forward or reverse should this arm center itself back up so the roller rocker is back in the valley of the arm when in gear? It seems to me that it should or the ignition system would be grounded constantly when in gear. Mine doesn't center back up. With the cable disconnected it does. This leads me to believe the cable is sticking holding the arm from returning to center.

Yup, that's correct.

#2- With an ohmmeter connected to the switch I have continuity at all times when shifted into reverse but no continuity in forward. I have bent the arm on the switch but I can't seem to bend it quite enough to make continuity in forward. I find it odd that, even with the cables disconnected and operating the lever with the y-spring on it by hand I still get no continuity in forward

You shouldn't have continuity in gear--that switch should ground momentarily when coming out of gear. Otherwise the arm should be centered and the switch open.

#3- I am inclined to replace the shift cable regardless, but the one that I have found as a replacement is an "aft" design as opposed to a "fore" design. Evidently the "fore" design is obsolete. The supplier said that it should work fine but that I will need to retap/rethread a new hole. There are no directions with the kit, but they said that everyone that replaces their cables have to do this. Is anyone familiar with this? Do I need to drill a new hole or is there an existing hole that just needs to be threaded?
Any help on this would be greatly appreciated-

There's plenty of info in doing that retrofit. No new holes necessary. Haven't done it, but IIRC the only trick is using a non-tapered tap. As a stop gap, you could disconnect the switch, which would keep it from stalling. It would also prevent you from coming out of gear with the engine running. Not particularly safe either though.

 

[mr 88]

Your first post descibes a choke that is not set up properly and has nothing to do with your shift interupter.

 

[thermalfinder]

Thank You everyone for the suggestions so far.
I have ruled out the shift interrupter because it only dies when cold shifting into gear.
I agree, Mr. 88 that it does sound like a choke issue, but I have brought the carb into a very reputable carb rebuild shop and they insist that it is working properly. (My gut feeling was that it is a fuel issue, but then I I got onto the interrupter switch idea.)
The choke plate opens all the way when warm, and the cold run fast idle is actually controlled with the shift/accelerator lever- evidently this is how carbureted boats were designed- they don't have a fast idle cam on the carb linkage. Which is smart- I wouldn't want my idle to stick at 1800rpm-
I reinstalled the carb today and also converted the distributor to electronic ignition and eliminated the points/condenser- although I am not the least bit optimistic that it is electrical- it really seems like fuel and starts back up after it dies-
I also had the idea that the engine isn't warming up quickly enough so the fuel doesn't get warm and atomize the way that it is supposed to. The engine never gets about 150 degrees (according to the gauge, anyway) but I understand that this is normal so that the salt water doesn't crystalize in the cooling system- it is running at the temperature that the system is designed for.
I am going to bring it out on the water tomorrow and see what happens.
I will keep you guys posted- thanks again for the suggestions!

 

[Bt Doctur]

disconnect the lower shift cable from the plate, apply grease to your thumb and index finger, try to shift outdrive. you should be able to move the black plastic with very little pressure. being a "only cold" problem may be because the shift arm,rod, and slide are a bit tight from corrosion and the heat and water flow loosens it up some and the problem goes away.need to pull the drive to help isolate the sticking problem

 

[thermalfinder]

Thank You Bt Doctur- from what I am hearing here though is that the interrupter switch only engages when shifting out of gear- not into gear. Mine only seems to die when shifting into gear. Could it still be the issue?

 

[Bt Doctur]

the switch DOES NOT MOVE on land on earmuffs going into or out of gear. If it does the lower cable needs to be replaced.

 

[mr 88]

You should be able to adjust the choke by loosening the three screws that hold the cover plate and then turn the cover plate one direction a "notch" at a time and see if that improves it.Mine ended up all the way to the right a smiggen past the last mark.The plate is marked at dead center and 4-5 notches on either side of that mark. The choke [and idle circuit] cannot be set up properly untill its on the engine and running in real world conditionsSo the rebuilder may have it set up per instructions in his shop but you need it running and in the water,not on muffs to do it correctly.Forget about the interupter switch that is not your problem.

 

[thermalfinder]

Thanks all. It rained cats and dogs in Seattle all day (go figure) so I wasn't able to check anything out on the boat to let you know what I came up with. I will keep you all posted!

 

[cmatheny1]

Since it only dies when shifting into gear when cold, I doubt it's a cable or interrupter issue. More likely, carb, fuel or ignition. Sounds like you covered part of these already. Have you replaced the fuel filter? If not, do so ASAP. Even when they look clean, they aren't. Cheap and easy. Also, did you pull the plugs yet? Another cheap and easy one to rule out...

 

[philbullet]

Iam no expert but every time i had the same trouble as u are having i've change the shift cable and adjust while in water.(u have to have back preasure on prop)Solved my problem.The cable has to be in good shape,any resistance in cable will make the interrupter switch not work properly.It seem that i have to do this every 2-4 years.1st. time was the retro fit.
Iam prety good at rmoving out drive now.lol

 

[thermalfinder]

I took the boat out today and it ran like a champ- no stalling when cold shifting. I am not exactly sure what fixed it, but fairly certain that it was the conversion from standard ignition to electronic ignition. I also replaced the coil because the electronic ignition required a coil with a secondary resistance of over 3 ohms and the existing coil only had 1.2 ohms. It appears that the hotter spark did the trick. I was about to replace the shift cable, and even bought one online, but it moves so freely when disconnected from the shift plate. I still need to ease it into gear, so I still have some adjusting to do, but the dying issue didn't occur today. And I caught a 10lb Coho to boot, so a pretty good day!
Thank You everyone for your posts!! I really appreciate all of the feed back!!
This is a great forum- hopefully I can return the favor and help you guys with an issue someday! (and time will tell if my problem is actually permanently solved or not)