Adjust Mercruiser Alpha 1 Stern Drive Shift Linkage
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- čas přidán 29. 09. 2022
- How to check and adjust Mercruiser Alpha1 stern drive shift system: My 2018 Mercruiser 4.5 Liter Alpha 1 has a problem shifting out of reverse, where it will not always disengage and come to neutral. Sometimes it hangs in reverse and stalls the engine. I will go through the process of checking the shift cable for lash and travel, intermediate stern drive cable lash and adjustment, adjusting the shift interrupt switch, and making the final cable adjustment. My boat is in the water for this investigation, so I am making adjustments and testing with my boat partially suspended on my boat hoist and the engine running. Caution: Testing in the water like this requires special care for safety to be sure that the boat is either secured so that it can't move, or that there is someone to assist if testing out on the open water. I am testing using my boat hoist, but I must be sure that the hoist is strong enough to take the stress of running in gear so that it isn't damaged.
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Wow, what a lot of effort!
One note, hopefully helpful to folks checking in 1+ year later:
For the lower shift cable, early Mercruisers had a spec of 5-7/8” rather than 6” center-to-center. Around the late 90’s, that changed to 6” instead. I don’t know how you might have gotten an early cable in a newer boat, but they started dimpling them so they couldn’t be adjusted. EXCEPT you can use a 1/8” bit to drill out the dimples (not too deeply) and restore adjustment!
On my boat, the upper (remote) cable doesn’t adjust at the barrel nut. That bit just swivels around the cable, but can be clipped at one of two fixed starting positions. The adjustment is made at the cable tip, with a jamb nut. Must be a weird after market thing. It’s given me fits making my adjustments.
Rare indeed to watch someone with an engineer's grasp of principles, a mechanic's attention to specs in the book, and real-world wrench-twisting knowledge. I have an elderly 120 in a Seaswirl with the reverse gear sticking syndrome. Your compensation technique really explains the relationship between the two control cables. I was tied to factory specs and wondering why I was not getting the result I wanted. Now I'm empowered to fiddle with the adjustments a bit. A big thumbs up and THANKS!!
You're welcome! And, thank you for your kind comments.
I had the same issue I ended up buying a new spring and doubled them up. Been golden ever since
Great video and with giving so much detail, really helpful. I have a similar problem and am finding the shift lever stiffer coming from reverse to neutral. Works great when out of the water but as soon as the shift interruption plate gets involved when in water it becomes much stiffer. Didn’t realise you can adjust the switch but also think the spring seems overly stiff also. Would be great to see what your shifter travel looks like when under load if possible
If it works with proper effort with the engine off, you may want to check the adjustment on that shift interrupt switch. The shift interrupt switch is intended to do two things, it has two ramps. First, it cuts power for an instant when you are shifting into gear to take load off the dog clutch teeth on the lower unit gears. Second, it should take the load off the gears to help them disengage. In other words, if you are trying to slide the dog clutch teeth apart with engine power on them, the effort will be higher. The switch should cut power momentarily to help the gears release. If it doesn't cut power or doesn't cut power until you move the shift lever further, the effort would be higher.
@@bitsofwisdom460fantastic, thanks. That sounds logical and i’ll have a good look at it friday. Best wishes.
Glad it's not just me with this exact problem...... three years later and still tinkering with Merc 4.5L to find the adjustment sweet spot..... still gives me issue when going from reverse back to neutral.... stays in gear and hits the interruptor switch..... engine will die if I don't "jiggle" or push the throttle at the helm forward slightly to get it to go into neutral and take the pressure off the interruptor switch.... this video gives me some ideas when I try again!
Yes, that is what I was having. Really a problem when you're trying to dock and the engine stalls while maneuvering. It seems that my compromise adjustment is working for right now.
@Bits of Wisdom
yep.... docking becomes a pain when the engine dies at the exact moment when you need to maneuver with in and out of gear movements........ im still troubleshooting, but I'm not going to let it keep me off the water. Just dealing with it for now... i will have another "tinker with it" session later this summer....
Hi MerCruiser Alpha one leg owners
The problem some of you have described with the motor diing on shifting has been the same problem that I have experienced on and off over the past two years with my Alpha 1 Stern drive second generation on a 3 L mercruiser inboard. The engine cuts out because the ignition interrupt switch activates, as it should, on the initial gear shift into forward or reverse, but it does not come back to the neutral position before the engine stops. What should happen is the interrupt switch activates momentarily to kill the motor to allow the gear shift without any torque, so it does not grind going into gear, and coming out of gear, it needs the engine killed momentarily to allow it to fall into neutral, otherwise it says in gear.
The most common cause for this problem is too much friction in the stern drive cable, so the return to centre spring on the interrupt cam plate does not have the force to move the cable back to the neutral position. The friction can be caused by a worn or damaged or poorly lubricated stern drive cable or binding of the cable through the penetrations into the gearbox. I have had limited success fixing the problem by replacing the stern drive cable and seals, which cured the problem for about 6 months before it returned, intermittently when the motor was hot.
On my latest service which included taking the leg off for an oil change and impeller change, I asked the mechanic if he could diagnose and fux the problem. He double checkef if the stern drive cable linkage was at all sticky or there were any problems that could be causing the shift interrupt sticking problem. He reported that there were not, and he fitted a new linkage plate as he reported that this had cured the problem with some of his other clients. He adjusted everything up to specification and I had about 1 hours worth of trouble free gear shifting before the problem returned.
The problem now is that every time it shifts into forward the engine will die. Reverse shifting is not a problem. To keep us out on the water, I have had my wife or one of the children hold the interrupt switch cam plate in the neutral position whilst I put the boat into forward. This is far from ideal, but otherwise the boat won't go.
I have now added an additional plate onto the gear shift plate to allow me to mount a tension spring that assists the interrupt switch return to neutral on forward selection. I will water test this tomorrow and hopefully it works. If it works, I will post a video on CZcams about what I did, so others can copy it.
The mercruiser Alpha 1 leg gear shift design with the manual shift interrupt switch arrangement that relies on the spring force of the interrupt cam plate to counteract the gearbox and shift cable is not a robust design at all. As soon as any friction builds up in the stern leg to control plate linkage is causes problems. This design problem is the main reason that I am actually going to sell my boat, and probably never buy another boat with a stern drive again.
I find it hard to believe that a reputable company like MerCruiser manufacturered such a temperamental design, that could leave a non-technical person stranded at sea.
@stevefewtrell1453 that is good to know that it's a tough issue to fix.... I already replaced the shift cable and was surprised to see that it did absolutely nothing to fix the problem..... it seems to just be a poor design.....
So I have an older stern drive - probably the original 40 year old lower shift cable. From what you found, (a shorter than 6" adjustment distance) a question:
Does it follow that if I were to lengthen that adjustment beyond the factory spec, let's say toward 6 1/8" or so, would that be adjusting in the correct barrel in the correct direction to solve the sticking in reverse situation?
I think that you will find that if the lower cable (to the stern drive) is short, the upper cable (to the driver's shift lever) will also need to be short so that when you pull the shifter back to neutral, the lower cable moves far enough to disengage reverse before the handle reaches neutral. Reverse is when the lower cable is extended on the standard RH drives. The official book adjustments are a little confusing because the factory wants some additional length (or turns) to account for slack in the cable assemblies. I started by using the factory (as delivered) adjustment and shortened the upper cable adjustment from there. If you have an older drive, just watch out for the pitch of the screw threads on the cable, they were once a coarser pitch
The 6 “ measurement it to “center” clutch dog in its travel. Older units typically have “accumulated” wear in all components ie gears,dog,crank,spool,splines and cable lining. So you’ll be fighting all that.
Wow- u got a boat too - i have a bayliner mercruiser alpha one
Yes, I actually have two for the last few years. Long story, but I have two places to use a boat that are a considerable distance apart and it's cumbersome to get them in and out. So, I have a 1998 and a 2018. If you take care of them, they will run a long time. I like the Mercruiser stern drives. Bayliner makes some nice boats.
@@bitsofwisdom460 My 17.5 ft bayliner has the 4 cylinder "iron duke" chevy motor. good on gas - long life more than enough. 2007
@@budsodalsky I started with a 17 ft Rinker back in the '80s with that same 4 cyl engine and the first year Alpha 1. It was a great package, and yes, great on gas. I decided to move up in size when the family grew. When my 3 children plus friends or grandparents joined us, we were challenging the weight capacity and the engine was struggling a little. We usually ran on a smaller lake and we needed a little more power to get up on plane in a shorter distance. I could have tinkered with a lower pitch prop, but we were close to max weight anyway. The Chaparrals have a 10 to 12 person capacity, so we can take nearly all my children and grandchildren at the same time.
Hello! Thank you for the video. Just bought a used 2020 stingray with the merc 4.5 that has this exact issue, and I have scoured the net looking for just this video. My wife will not drive the boat because of this issue. I will be trying these adjustments this weekend. Where did you get a service manual for the engine?
If you go to the Mercury / Mercuiser web site, they sell the official factory manuals. There are two manuals, one for the engine and one for the stern drive unit. Actually, there is also a parts manual with the exploded views and a parts list. The order process will normally ask for your serial / model numbers so that they can be sure to ship the correct manual. They are not inexpensive, but I have found them very helpful. If you save one trip to the dealer, it can pay for itself.
Thanks Again!
@@epicshroomie5005 You're welcome
I appreciate your effort to put the video together but this should be about 5 minutes long. No need to preface, re-explain, rationalize, etc.
I understand your concern and agree that it is long. And, you're right that if the system just needed a quick tweak, my video is overkill. However, the dealer did the 5 minute check and couldn't / didn't fix it. I have been through the short version myself as well and it didn't work. I struggled with this for several years. The Mercruiser service manual instructions for the this process are two sections of 10 pages each. When the system doesn't work properly, you need to do a careful deep dive through all 20 pages. Had I not done that, I would not have found the factory defective cable to the outdrive. Perhaps my explanation could be shorter, but sometimes you need to explain the "why" so when the process doesn't work as intended, you can deduce where to go next.
Way to much explanation, not enough work,