Merc 4HP Gnat running, shift issue

[Tinumium]

So with some help I got the 4hp gnat running, and it sounds good too. The issue now, is that the previous owner had the shift knob (plastic) off. As it turns out the unit is always in forward, no mater how I turn the shifter shaft.

Should I start by replacing the shift shaft or start at the lower unit? My hunch is the previous owner knew nothing at all about engines and was just ordering parts to throw at it.

Item 6 and 5 are in the bag, I am not sure how these would have anything to do with the lack of shifting.

 

[oldman570]

Re: Merc 4HP Gnat running, shift issue

If you have all the parts shown in the diagram together and the LU will not shift and the shifting rod moves up and down when you try to shift it, then there is trouble in the LU. If the rod dose not move when you move the shift handle then the roll pin that goes thru the shift shaft at where it hooks to the shift rod is probably missing or broke. JMO
Oldman570

 

[Tinumium]

Re: Merc 4HP Gnat running, shift issue

Thanks!

Everything is together aside from item 5/6. Where can I observe the shifting rod moving (removing the lower unit)? Newish to marine motors, but more than familiar with other motors and happy to dig in wherever needed. I just try to minimize any mistakes

 

[cr2k]

Re: Merc 4HP Gnat running, shift issue

If he used it as a kicker I could see why it would always be in gear. I would drop the lower and (put the fin in a rag lined vice to hold it) work the shift to make sure it shifts then (replace the impeller while you are here) properly reassemble making sure all the parts (shift handle)in the engine pan are properly installed.

 

[Tinumium]

Re: Merc 4HP Gnat running, shift issue

Thank you, Any tips on dropping the lower? Drain lube, unbolt, remove?

 

[jbjennings]

Re: Merc 4HP Gnat running, shift issue

No need to drain the lube to remove the lower unit. Remove the mounting bolts and it should slide out. Mercs of that age usuallly have splined shaft that slides out of a collar on the end of a shift shaft. If the splines are not aligned correctly, that could be a problem. Make sure upon reinstallation that the shift splines are aligned correctly, and that the water tube goes back in the grommet correctly.
JBJ

 

[Tinumium]

Re: Merc 4HP Gnat running, shift issue

Ok, sounds easy enough. I knew this one was a little bit of a project when I got it but that's ok by me. Thank you very much.

 

[Tinumium]

Re: Merc 4HP Gnat running, shift issue

Lower took two bolts to remove. The shifter rod came out with it! The top of it has a hole where what looks like a cotter pin or similar used to be.

1.) Do I have to remove the motor from the bottom cowl to correctly install the shift rod and pin?

2.) While I had the lower off I put the end of the shift rod in , tried up and down and turning all around and it just stays in gear. Am I doing something wrong or is the lower shot?

Thanks!

 

[jbjennings]

Re: Merc 4HP Gnat running, shift issue

I hate to say it, but I think that is a forward, neutral only shifting lower unit. I did not see a reverse gear in the parts diagram. I believe you may have to pull the powerhead (not as hard as it sounds) to get the shift shaft back in the bell crank under the pwoerhead. I thought you may have mentioned it was f-N-R, and would most likely have the splined shift rod. Have you tried pushing down on the rod and turning the prop at the same time? Or turning the prop and pulling up on the rod? I'm thinking the shift rod may have already been disconnected at the bell crank under the powerhead or it would not have come out. Anyway, I hope this helps. Usually the F-N only lower units will work, unless the parts in the lower unit have rust fused together. How does the lower unit oil look?
Sorry about the bad advice on the shift rod,
JBJ

 

[racerone]

Re: Merc 4HP Gnat running, shift issue

Deleted

 

[Tinumium]

Re: Merc 4HP Gnat running, shift issue

So the shift rod, the end that goes into the lower is keyed (not round, more like half round with one straight side). Is that what you mean? If pretty much just goes into the hole in the lower unit and twists left and right? Sorry if I am confusing. If need be I will go take some pics.

It looks like there are 6-7 bolts holding the powerhead on, just unbolt and lift off seems right.

No idea on the lower units oil yet, but it did turn well when I ran the motor.

I appreciate the help, this is a learning experience for me.

 

[racerone]

Re: Merc 4HP Gnat running, shift issue

Should post serial # of this motor.

 

[Tinumium]

Re: Merc 4HP Gnat running, shift issue

9090748 , two cylinder gnat

 

[jbjennings]

Re: Merc 4HP Gnat running, shift issue

I wish I could help. I still think this is a F-N only motor. It has a clutch release spring but no reverse gear. I am thinking by the shape of the shift shaft that the clutch disengages when the rod goes down, not by rotating the shaft. I could be wrong, however, since I've never worked on one of these. Hopefully someone with actual knowledge will contribute to your thread. I hope I have not steered you too badly in the wrong direction. Here's a link to some parts diagrams for your motor: http://www.*****************/parts/...980-bel/gear-housing-assembly-propeller-shaft
Good luck,
JBJ

 

[Tinumium]

Re: Merc 4HP Gnat running, shift issue

Thanks again for the help. Ok, so essentially when the shift rod is pushed down, it should disengage the clutch and put the lower end into neutral? If so, I need to get a screwdriver in the and see if it can disengage the clutch. Is the clutch serviceable?

 

[jbjennings]

Re: Merc 4HP Gnat running, shift issue

Is the shift rod still in the midsection and not in the lower unit?

 

[Tinumium]

Re: Merc 4HP Gnat running, shift issue

Its out now, it was not connected to the shifter up top. Nothing seem to hold it into the lower, it just sort of inserts...

 

[jbjennings]

Re: Merc 4HP Gnat running, shift issue

I would figure out how to get it to shift. The shift rod needs to be in the lower unit to prevent water from leaking into the lower unit. It's a simple mechanism, but I'm not sure how that particular one works. Once you have the lower unit shifting, have clean oil in it, and a new impeller for the water pump, reinstall the lower unit and you'll have to pull the powerhead to get the shift shaft connected properly to the bell crank. Once connected to the bell crank, it should keep it in the proper position for the lower unit.
Wish I could help more,
JBJ

 

[racerone]

Re: Merc 4HP Gnat running, shift issue

When the shift rod is pushed down it catches on the tab of the drive spring.-----This disengages the wrap spring.----Wrap springs have been popular on small motors as far back as the early 1950's and it is simple.

 

[Tinumium]

Re: Merc 4HP Gnat running, shift issue

So maybe the drive spring is stuck? Any easy way to get access or could I try some wd40? I cant see down that hole even with a flashlight (good 3+ inches) down I think.