"skip" in gear at low speed? '91 Blackmax 150

[santuitman01]

Hello all
I have a 91 Merc blackmax 150 on a 20ft Wellcraft. The motor runs well but occasionally there seems to be a jump or skip in forward gear at low speed. Once you throttle up it is fine. In reverse I don't seem to notice it and the lower unit gear oil is clean. I can't seem to make it happen repeatably. Any ideas?
Thanks in Advance

 

[sschefer]

Re: "skip" in gear at low speed? '91 Blackmax 150

Hello all
I have a 91 Merc blackmax 150 on a 20ft Wellcraft. The motor runs well but occasionally there seems to be a jump or skip in forward gear at low speed. Once you throttle up it is fine. In reverse I don't seem to notice it and the lower unit gear oil is clean. I can't seem to make it happen repeatably. Any ideas?
Thanks in Advance

Clutch dogs in the Lower Unit are getting worn. Eventually it will start to chatter at high speeds and then finally it will just not engage in forward at all.

This fix is probably going to run you about 500.00 to have it done by a shop. Not much less if you do it yourself after you buy the tools.

 

[santuitman01]

Re: "skip" in gear at low speed? '91 Blackmax 150

Hi
Thanks for the reply and sorry it has taken this long to say it! I'll have to start figuring out whether to try and go the season or not. Needless to say marine mechanics are quite busy this time of year.

 

[achris]

Re: "skip" in gear at low speed? '91 Blackmax 150

Can someone please explain to me what a 'skip' is. This forum is the only place I have ever hear the word used in an engine context. I only know of 2 types of 'skip'.

1. noun: Large waste bin, usually transported on the back of a truck.
2. verb: to jump over a spinning rope; or to run with an alternate gait.

Thanks in advance....

Chris........

 

[santuitman01]

Re: "skip" in gear at low speed? '91 Blackmax 150

Actually it's hard to explain the "thing" that the motor does. I called it a skip or jump because I was ata loss of words. It is almost like your prop hits something or your motor jumps out of gear but only for a second and then it's fine again. Maybe it is more like a pound or knock but you feel it more that you hear it.

 

[achris]

Re: "skip" in gear at low speed? '91 Blackmax 150

So you're saying it's like the engine's running on 5 cylinders and every so often the 6th cylinder fires and then drops out again? We call this 'surging'. Or maybe your prop is ventilating or the hub is slipping.

Chris...........

 

[santuitman01]

Re: "skip" in gear at low speed? '91 Blackmax 150

No, it's more like dropping in and out of gear but for such a short period of time that it's not something you could really do yourself. the rpms stay constant and smooth. Maybe "chunk" or "clunk" would be a better description.
Also only in forward that I've noticed and under ~1500 rpm, I believe.

 

[achris]

Re: "skip" in gear at low speed? '91 Blackmax 150

Check the prop nut is tight... and the shift cable is adjusted correctly.

 

[santuitman01]

Re: "skip" in gear at low speed? '91 Blackmax 150

okay, I'll check those. Hopefully in the next couple of days. Seems like there is always something getting in the way of boating and maintainence

 

[sschefer]

Re: "skip" in gear at low speed? '91 Blackmax 150

My 100 did the very same thing that you're describing. It only occured under load and around 15-1800 RPM. Kind of like a bam... bam, bam.. Later it begin to rattle at around 3500 RPM and finally it started to ratchet if I shut down in gear. Mine was bad clutch dogs that just finally wore out. I also replaced the forward gear as it was also worn.

 

[santuitman01]

Re: "skip" in gear at low speed? '91 Blackmax 150

I have to say I'm hoping for a stretched or misaligned cable but don't think I'll be that lucky

 

[santuitman01]

Re: "skip" in gear at low speed? '91 Blackmax 150

An update on incase it helps others...
On the suggestion to check the cable and prop nut. The prop nut is fine but the shift cable was not quite correct. In neutral the alignment was not centered but was slightly toward the reverse end of the giude. I was able to adjust the cable so it came up right on neutral and that seems to have worked. No skip as far as I can tell. I'm guessing the cable has stretched and thats now on the list for this winter.
Chris - Thanks very much for the suggestion!!!