Engine stalling when shifting from neutral to forward when hot on 153 cu.in 120 4cyl

[redgoat]

Last summer I replaced a shift interrupter switch (39671A3) on my 153 cu.in. 120 hp 4cyl Mercruiser. I considered my self lucky to find this NLA part at a local dealership. This seemed to solve my forward to neutral binding up problem. My perennial problem for many years was the stalling when hot when I would shift from neutral to forward or neutral to reverse. The engine would die. It would usually start right up again but would die when put into gear. Today it ran flawlessly for 90 minutes. An hour later it ran fine for an hour then started to idle rough and even stall. It would restart quickly but would die promptly when put into forward gear. I have thoroughly rebuilt the carb, recently installed an electronic ignition, new fuel pump and fuel filter, new plug wires and plugs, new coil, double gasket on carb base, adjusted needle valves, and set timing. I am aware of heat soak so I run my blower constantly to remove hot air from engine compartment. This Mercruiser engine is 45 years old but has been meticulously maintained. This problem existed on my old points and condenser ignition before I went electronic.

 

[achris]

Re: Engine stalling when shifting from neutral to forward when hot on 153 cu.in 120 4

I remember your thread on the points conversion... Glad it runs nice now... The shift problem could be the lower shift cable. If that's the same age as the engine then that is probably the problem, and it will get worst with time...

Chris........

 

[redgoat]

Re: Engine stalling when shifting from neutral to forward when hot on 153 cu.in 120 4

Thanks Chris for your suggestion. You were absolutely correct on my electronic conversion wire connection. I'm sure you are correct on my shift problem. Will have to have it checked out at repair shop as I think this is likely beyond my level of expertise. Just curious--how does a shift cable relate to my problem? Is there an upper shift cable as well? Back in '07 I had a shift cable (part no. 73723A01) replaced due to excessive corrosion and paid $420 labor plus parts for a shift cable, slide shift, bellows, 3 seals and gasket set. Could this be the shift cable you are referring to? My boat runs fantastic when underway, at top speed, and pulling a skier.

 

[achris]

Re: Engine stalling when shifting from neutral to forward when hot on 153 cu.in 120 4

OK.. you had the cable replaced 5 years ago.. That shouldn't be the problem then.... It could be the adjustment... Here's a video of the shift cable adjustment.... http://youtu.be/-s_tgevX2aI
And here's how the shift interrupt system works (you'll see how the cable can cause a stall if it's binding or out of adjustment) http://forums.iboats.com/showthread.php?p=1930449#post1930449

 

[redgoat]

Re: Engine stalling when shifting from neutral to forward when hot on 153 cu.in 120 4

Thanks again for your reply. After viewing the videos, I can see how the shift cable and the shift interrupt system are closely related and a cable out of adjustment could trigger the kill switch when it's not supposed to. Will take boat to shop tomorrow.

 

[redgoat]

Re: Engine stalling when shifting from neutral to forward when hot on 153 cu.in 120 4

UPDATE
Got boat back today from repair shop and technician could not find anything wrong. He said that the lower shift cable was right on specs and could not get boat to act up. He further stated that the shift interrupter switch has nothing to do with shifting from neutral to forward. He said maybe I had some old or bad gas. I did store boat last fall with 1/2 tank but added Stabil to gas. When I got home today, I drained all the gas and will start out with fresh gas on my next trip and add a bottle of Techron. I am still not sure his diagnosis is completely accurate about my problem. As stated before, on my 1st time out this year with the engine got hot after an hour or so of running it hesitated and at one point stalled. It restarted quickly but when I put it into forward gear it was as though someone immediately turned off the ignition key as the engine died. Repeated starts would result in the same outcome with the engine promptly dying. I had to be towed to dock. Could his gas theory have some merit and my problem should be solved for future outings? Or is that shift interrupter switch out of sinc. Or is it something else entirely. The mechanic maintains that the lower shift cable is functioning correctly. Any suggestions?

 

[achris]

Re: Engine stalling when shifting from neutral to forward when hot on 153 cu.in 120 4

..... He further stated that the shift interrupter switch has nothing to do with shifting from neutral to forward. ...

He is absolutely correct, when everything is working correctly...

BUT, when the shift cable is sticky then it can trip the switch and kill the engine when shifting into gear (this is usually the first sign of the cable going bad)... You need someone else out with you (you shouldn't be able to see the lever moving when it's run on flushers)... When it's acting up, have them shift gear while you watch the interrupt switch... WATCH CLOSELY, it only take a fraction of a second to kill the engine... If you see the lever assembly move as the drive goes into gear... .You, most likely, have a lower shift cable problem (or something 'downstream' of that)....

 

[redgoat]

Re: Engine stalling when shifting from neutral to forward when hot on 153 cu.in 120 4

Ok. I guess I will have to return to the lake to see if engine will act up again in order to determine if the lever assembly on the interrupt switch moves when shifted into forward. Thus if I understand your post, the lever assembly should not move at all when shifting into forward or reverse. If it does, then I likely have a problem with my lower shift cable and a replacement should be done. I hope I don't have to be towed again!

 

[achris]

Re: Engine stalling when shifting from neutral to forward when hot on 153 cu.in 120 4

As a TEMPORARY fix (DEFINITELY not long term) so you can get back to the jetty/ramp/dock under your own steam, disconnect one of the interrupt switch wires (doesn't matter which one), but don't let it touch ground.... When you want to shift OUT of gear, you will need to either, do it was you come off speed (so there is no load on the propeller), or shut your engine down to do it....

As I said... This is a TEMPORARY/get you back home procedure... Running permanently like this will cause damage in the longterm...

Chris.....

 

[redgoat]

Re: Engine stalling when shifting from neutral to forward when hot on 153 cu.in 120 4

Thanks Chris for the posts.
If that lower shift cable is determined to be defective, is there typically other parts that need to be replaced as well in the process of replacing the cable. Or can the cable be replaced as a single unit and then adjusted accordingly. I've seen prices for genuine Mercury replacement cables for my specific application on the net running from $45 to $149 for the same cable (73723A01).

 

[achris]

Re: Engine stalling when shifting from neutral to forward when hot on 153 cu.in 120 4

That question can only be answered once you have the drive off.... Be careful on the cheaper cables... Make sure there are genuine Merc cables...

 

[redgoat]

Re: Engine stalling when shifting from neutral to forward when hot on 153 cu.in 120 4

UPDATE.
It's been over a month since my last post on this boat issue. My second trip out resulted in the same engine symptoms and another tow back to dock when engine would not start after an hour of running. A different repair shop could not find anything wrong either but did adjust the air-to-fuel needle screws and the idle. This has really been frustrating. Two trips to the lake and two tows back to dock. My third time out after the second repair shop worked on it resulted in the same problem as before. This time I hung around the dock so as not to be towed a third time. The next day IT DAWNED ON ME. I'll bet my problem all along was that new Sierra Delco Electronic Conversion Kit that I installed before my first trip out this year. I decide to remove the electronic ignition and reinstall my points and condenser. Set the dwell and timing and took it out today for a test run. IT RAN FANTASTIC. . . just like it did when I put it into storage last fall and for years prior. So I solved my own problem. Perhaps my ballast resistor could not handle this device or maybe my newer coil was not adequate for it or maybe the conversion kit was just plain defective. In any event, I sticking with my points and condenser and the heck with electronic ignition. Some responders on this website have said that if your electronic ignition goes bad you are dead in the water. Perhaps this whole experience is a good example of the old saying "IF IT AIN'T BROKE, DON'T FIX IT."