Bang bang bang is not a good sound

[shoestringmariner]

Hey everyone, I finally managed to do a run with the 1976 Mercury 650 that I recently acquired. Was harder starting in the water than it was on muffs, but once warmed up, ran quite well and at all speeds.

Reverse gear however was a different story. Anything other than idle in reverse went bang bang bang, like there was teeth missing off the gear. The oil in the gearcase when I bought it was new. It was raining hard when I got home tonight so I didn’t check to see if there was water in it after today’s run.

Thoughts? Is it odd that reverse gear has a problem not forward year?

[billw]

Of course, you’re going to want to recheck the oil after your run. Drain it and refill with fresh, again, just to be sure. You should have the first year of stainless shafts. It sounds like you may be jumping in and out of reverse gear. My feeling is that you will need to adjust the shift cable for a little more throw into reverse. Also, keep in mind that you must raise and lower the engine with the control placed in FORWARD gear. It’s just a Merc thing. NOT doing this may leave you with a reverse lock hook that is sitting on TOP of the tilt angle adjusting rod, not AROUND it, like it should be. That also would make the movement of the shift mechanism less likely to have its full travel.

Long live American manufacturing!

[shoestringmariner]

This is great to know. I hope that’s all it is. I can hear it go “kerchunk” into reverse. And idle reverse works well, it’s just that when I apply any acceleration to it, it goes bang bang. I will check it out and see if I can figure it out. Thanks again

[dave-bernard]

If the reverse cable adjustment wont do the trick then the upper shift shaft is bent. call me for a repair for that. 11 194 310 7086. Dave.

[shoestringmariner]

Thanks Dave, I appreciate that.

So I checked the fluid again. It seems a lot thinner than it was when first brought home six weeks ago. Then again it was really cold out at that time. It’s a lot runnier than I’d expect for gear oil. It is still sort of an opaque colour with a blueish tint. I think I’m gonna change and run it again and see.

As for adjustment, I don’t know what I’m looking for. It seems that the cable is as far back as possible in it’s slot when in reverse. I will try and post a picture.

One thing I did notice is that there is a lot of play in this motor. It will go side to side and I can lift it slightly and get it to move about an inch away from the transom when locked. wondering if all the bushings are worn out on this thing. Not sure if that has any bearing on this issue or not.

[jerry-ahrens]

Keep in mind that it won’t take to many of those noises to round off the clutch dog and reverse gear ramps. I would fix it before taking another boat ride.

[shoestringmariner]

Thank you, That sounds plausible.

I was told NOT to granny shift this thing into gear which is exactly what I was doing. Because it’s an old boat an old motor I was treating it gently. Does that sound about right? Somebody else also mentioned that the last person who did an impeller be not have lined up the cam properly meaning it sort of goes into gear. Might be time to open it up to change the impeller and see how it looks

[dockbuster1]

Some times when the upper mounts have disintegrated the shift shaft binds .you should not be able to move the leg and powerhead away from the swivel bracket the alchol in the gas attacks the rubber in the mounts causing them to fail the end result being a snapped shift shaft very dangerous if not addressed

[shoestringmariner]

Wow, thank you, I will look at this carefully and get it fixed before it hits water again

[shoestringmariner]

Tried it again last night, definitely don’t have reverse gear. It sounds worse to boot.

No problems in forward gear.

Would I be nuts to still use this temporarily (avoiding reverse) until I can do a tear down? (on vacation this week and want to go fishing)

I changed the oil. Didn’t see any shrapnel or filings

[Author]

Posts