Very difficult to shift into Neutral

[Rivergator]

Long time away from iboats. This is Rivergator. I had my boat now 3 times in the water for testing purposes and to make on the water adjustments. I couldn't be happier considering that I completely restored this Katrina wreck. I still need to do some upholstery and cosmetic work but all the technical/mechanical stuff is done and everything works good, but....there is always a but. I am having a very hard time shifting into neutral. I believe that my upper and lower shift cables are adjusted right. The drive works perfect. Solid gear engagement in Forward and the same in Reverse and a perfect Neutral. Prop spins freely and silently. Naturally I can shift easily into Neutral when out of the water but when in the water and there is a load on the prop, not so easy. As I proceed to shift into neutral the shift interrupt switch causes the engine wanting to die but as I get closer to the neutral position the gears just don't want to let go. Only after applying what I would call excessive force on the remote shifter will it finally shift into neutral. By that time the engine just about stalled. As a matter of fact if the situation on the water permits I actually allow the engine to die and then make the final push to the neutral position just to take it easy on the entire shift mechanism and the gears in the drive. Any idea why slipping into neutral is so hard?

 

[theorifice]

I have a similar problem right now with both engines. Often times, I can only apply the requisite force by shifting past the neutral position on the control. Once in a while, I'll get a smooth shift to neutral but it's rare.

Recently - have adjusted shift interrupt (cutoff) switch to the requisite 1/8" of travel before cutoff. No noticeable effect even though one engine's switch was out of adjustment. Have you checked this?

I've also checked idle RPMs (I used an audio based app) and it seemed "in the ball park). The value recorded was ~700-750 RPM under load so there is some room for improvement. I believe the spec is 650 RPM. Seems possible to adjust lower so I'll try that next. Another thing to check once tach arrives.

Note that I had removed the shift assist mechanism which helps shifting into neutral. I'll also try re-installing on one engine and check for improvement, with the understanding that shifting into forward or reverse will require more force.

I also suspect wear in the upper shift cable wear as a possible culprit but haven't performed any investigation yet.

 

[Scott Danforth]

Any idea why slipping into neutral is so hard?

because your lower shift cable is probably hanging up or the shift interrupt isnt working. The alpha drive is a dog clutch drive, so you have to take all load off the clutch to disengage it. that means momentarily killing the motor as you shift. that is the function of the shift interrupt switch. it literally interrupts the ignition

quick test, momentarily key off while shifting to neutral. bet it goes into neutral like butter.

 

[Rivergator]

1/8 of travel is about what my switch does before it closes, but I will double check again with my volt meter to see exactly when the switch closes. I believe my shift cables are in good order. I tested them out of the water with no propeller installed, engine running at about 1000 rpm and they shift into forward and reverse like cutting through butter, no binding or hanging up. Scott, read my post again. The interrupt switch is working. Yes, turning the engine off will make shifting easy but the engine is supposed to run, not die just slow down to relieve pressure on the dog clutch and it struggles doing that. The idle rpm is on the high side, I admit, between 800-1000. If I go any lower than that the engine has a tendency to stall when shifting into gear because of the momentary added load on the propeller. One thing Mercruiser doesn't have is to automatically increase the rpm a little bit to compensate for the added load on the prop like cars have, when shifting from park/neutral into drive the engine makes up automatically for the drop in rpm a transmission under load will cause. But I don't know if RPM has anything to do with shifting into neutral on an Alpha One drive because that's what the interrupt switch is for to facilitate that. Correct me if I am wrong, by all means.

 

[Bt Doctur]

if depressing the lever does not "stumble" the motor ,it means the switch IS NOT connected correctly

 

[Scott06]

1/8 of travel is about what my switch does before it closes, but I will double check again with my volt meter to see exactly when the switch closes. I believe my shift cables are in good order. I tested them out of the water with no propeller installed, engine running at about 1000 rpm and they shift into forward and reverse like cutting through butter, no binding or hanging up. Scott, read my post again. The interrupt switch is working. Yes, turning the engine off will make shifting easy but the engine is supposed to run, not die just slow down to relieve pressure on the dog clutch and it struggles doing that. The idle rpm is on the high side, I admit, between 800-1000. If I go any lower than that the engine has a tendency to stall when shifting into gear because of the momentary added load on the propeller. One thing Mercruiser doesn't have is to automatically increase the rpm a little bit to compensate for the added load on the prop like cars have, when shifting from park/neutral into drive the engine makes up automatically for the drop in rpm a transmission under load will cause. But I don't know if RPM has anything to do with shifting into neutral on an Alpha One drive because that's what the interrupt switch is for to facilitate that. Correct me if I am wrong, by all means.

with no propeller on the water doesn't mean anything. the load of the propeller with the back cut angle on the dog clutch teeth is what holds it in gear. Same as how you lock it in fwd by holding the prop CCW with a bungee on land... same as water pushing against prop blade...

the too high idle speed will make this more difficult. You should be on the water in gear at 650 rpm or so. If it is stalling going into gear, make sure the shift interrupt is not getting tripped going into gear, and adjust the carb so that it stays running (fatten up idle mix maybe, is timing correct?). should have no issue going into gear at 650 or so. When setting idle speed on the trailer typically set it 50-100 rpm higher than you want it on the water, then fine tune on the water and in gear.

if you are tripping the interrupt going into gear that is a sign the lower shift cable is dragging. easy way to tell is to remove cable from shift plate, it should move easily with two fingers only.

As BT mentions depress the interrupt and make sure it is causing a brief stumble, but willing to bet if you get your idle speed correct you can get it out of gear.

 

[Lou C]

1/8 of travel is about what my switch does before it closes, but I will double check again with my volt meter to see exactly when the switch closes. I believe my shift cables are in good order. I tested them out of the water with no propeller installed, engine running at about 1000 rpm and they shift into forward and reverse like cutting through butter, no binding or hanging up. Scott, read my post again. The interrupt switch is working. Yes, turning the engine off will make shifting easy but the engine is supposed to run, not die just slow down to relieve pressure on the dog clutch and it struggles doing that. The idle rpm is on the high side, I admit, between 800-1000. If I go any lower than that the engine has a tendency to stall when shifting into gear because of the momentary added load on the propeller. One thing Mercruiser doesn't have is to automatically increase the rpm a little bit to compensate for the added load on the prop like cars have, when shifting from park/neutral into drive the engine makes up automatically for the drop in rpm a transmission under load will cause. But I don't know if RPM has anything to do with shifting into neutral on an Alpha One drive because that's what the interrupt switch is for to facilitate that. Correct me if I am wrong, by all means.

Don't have merc experience but I know with the Cobra dog clutch, if the idle is up that high, the ESA system can't lower it enough to have an easy shift to neutral. I keep mine between 550-600 in gear in the water, that equates to 625 or so in neutral in the water, and it shifts with 2 finger pressure on the remote shifter. If you can't get a reliable idle at 600 in the water, something still isn't right (fuel mixture? vacuum leaks? etc).

 

[Scott Danforth]

at 800-1000 your idle is way too high

make sure the shift interrupt switch is working properly. you may need to swap your lower shift cable as they only last about 15 years

get your idle down to 600-650 RPM.

 

[Rivergator]

Scott06, I said no propeller OUT of the water for the purpose of testing the shift cables. They are smooth as can be just as they were 3 months ago when I did all the shift cable adjustments. I am pretty sure that the shift interrupt mechanism is working as intended. It does not activate going into gear only coming out of gear going into neutral when on the water. When I depress the interrupt switch manually it does not cause a brief stumble but will kill the engine as long as I keep it depressed. Is that the way it's supposed to be? I will work on the idle and see if I can get it to stabilize at around 700 or 750 and see if that makes a difference. It's gonna be a ***** to get to the air/fuel adjustment screw on the carburetor because it's hidden right snug behind the thermostat housing and I hate to mess with it because the engine is running so nice. The next time I am on the water I will tinker with lowering the idle speed first and see if that makes a difference.
Scott and Lou, I just caught your post. Idle speed seems to be the issue here. I will certainly concentrate on that that next time on the water. Thanks guys. I'll report back

 

[Scott Danforth]

yes, that is how it works, however with a load on the cable, the cable can hang up.

regarding the carb, just adjust the idle speed. leave the air/fuel adjustment alone. if the cable is pulling against the throttle, that will artificially set your idle different.

 

[Scott06]

Scott06, I said no propeller OUT of the water for the purpose of testing the shift cables. They are smooth as can be just as they were 3 months ago when I did all the shift cable adjustments. I am pretty sure that the shift interrupt mechanism is working as intended. It does not activate going into gear only coming out of gear going into neutral when on the water. When I depress the interrupt switch manually it does not cause a brief stumble but will kill the engine as long as I keep it depressed. Is that the way it's supposed to be? I will work on the idle and see if I can get it to stabilize at around 700 or 750 and see if that makes a difference. It's gonna be a ***** to get to the air/fuel adjustment screw on the carburetor because it's hidden right snug behind the thermostat housing and I hate to mess with it because the engine is running so nice. The next time I am on the water I will tinker with lowering the idle speed first and see if that makes a difference.
Scott and Lou, I just caught your post. Idle speed seems to be the issue here. I will certainly concentrate on that that next time on the water. Thanks guys. I'll report back

Ok misread it but it means the same thing (nothing). Totally different out of vs in the water.

Yes get your idle speed down. Not sure how it is running so nice if it wont idle at proper idle speed.... did you adjust the idle mix when you got it running? If you keep track of how many turns you adjust you can always put them back to the same spot ...

a flexible tool like this made for carb adjustment can help. I have a similar one with 1/4" drive on the end and a small socket.

Lisle 55250 Lisle Carburetor Adjusting Tools | Summit Racing

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What carb do you have Qjet or Mercarb?

 

[Lou C]

Those tools are the only way to get it right esp with Rochester carbs that have the idle mix screws under the float bowl. The Holley and Edelbrock designs are easier to get at.

 

[Bondo]

Ayuh,..... Welcome back gator,...... To fix yer idle problem, set the idle screw to 650/ 700 rpms(spec),....
It should be the same, in the water, or out, in gear, or not,.....
If it stalls, odds are it needs to be richened up abit,....

 

[Lou C]

I have found that I get a smoother running engine if I readjust the idle speed & mixture with the boat in the water; I feel the back pressure of the water against the exhaust makes a difference….550-600 in gear is ideal for dog clutch shifting

 

[kenny nunez]

A vacuum gauge helps with the boat in the water. Quadrajets are usually happy at 3 turns out. But the idle stop screw has to be set where the next circuit is not coming on. Looking down into the Venturi there should not be any fuel bubbling from the boosters.

 

[Lou C]

Yep that’s a good test. Make sure you’re running only on the idle system. If you turn the idle mix screws all the way in (gently) it should kill the engine. If not your throttle places are too far open, and you’re also running on the off idle or transition system.

 

[ROY WILLIAMS]

Long time away from iboats. This is Rivergator. I had my boat now 3 times in the water for testing purposes and to make on the water adjustments. I couldn't be happier considering that I completely restored this Katrina wreck. I still need to do some upholstery and cosmetic work but all the technical/mechanical stuff is done and everything works good, but....there is always a but. I am having a very hard time shifting into neutral. I believe that my upper and lower shift cables are adjusted right. The drive works perfect. Solid gear engagement in Forward and the same in Reverse and a perfect Neutral. Prop spins freely and silently. Naturally I can shift easily into Neutral when out of the water but when in the water and there is a load on the prop, not so easy. As I proceed to shift into neutral the shift interrupt switch causes the engine wanting to die but as I get closer to the neutral position the gears just don't want to let go. Only after applying what I would call excessive force on the remote shifter will it finally shift into neutral. By that time the engine just about stalled. As a matter of fact if the situation on the water permits I actually allow the engine to die and then make the final push to the neutral position just to take it easy on the entire shift mechanism and the gears in the drive. Any idea why slipping into neutral is so hard?

The shift cables the lubes and the grease .... the shift interrupt switch take it off cleaning and the grease ... so the interrupt cutout switch the metal and the ball is the of the metal variation switch .... switch level ..

the summer engine MCM470 boat 1978 the cables and the interrupt switch ... also the shift throttle control cable ..lubes/grease .....

 

[Rivergator]

Ok, I am back. To answer your questions. My carburetor is the Mercarb 2bbl #807764A1. Had the boat in the water today. I think the problem might be with the carburetor. I am unable to maintain an idle speed of 600 or even 700 when in neutral. The engine will always stall. When idling at around a 1000, the engine sounds good and normal and if it wasn't for the tach telling me the engine is doing about 1000, I would think I am close to 600, but obviously I am not. Is there a special circuit in the carb handling idling or is it all done by the fuel/air mixture needle. If there is a low rpm jet or something like this, it might be plugged up and causes the engine to stall below 1000 or so. Anything above that the engine seems to run fine, pulls through easily up to 3500 or so. If all of this is controlled by the fuel/air mixture setting then Bondo probably is right, make it a little richer. I will try that once I figure out some magic way that I can reach the fuel/air mixture screw. like I said the Mercarb butts right up against the thermostat housing and that's where the needle is. I actually did the adjustment according to the book before installing the carburetor and hoped for the best. Maybe a little adjustment is the answer to the problem

 

[Scott Danforth]

You need the flex tool

 

[Lou C]

Yep that’s the only way with the Rochester style carbs (the Mercarb is a slightly modified Rochester 2bbl IIRC). The Weber/Edelbrock & Holley carbs are much easier to adjust.