1989 4.3 W/OMC drive "thumb"

[haliburton Lk]

I have a 1989 Oliver with a 4.3 Merc and OMC drive, I sometimes get a thumb from the drive, like I hit something in the water, it doesn't happen all the time and a different speeds, no griding or nothing just a thump...HELP!

 

[Gary H NC]

Re: 1989 4.3 W/OMC drive "thumb"

I'm confused! Is it a Mercruiser or OMC?

 

[haliburton Lk]

Re: 1989 4.3 W/OMC drive "thumb"

Omc

 

[danond]

Re: 1989 4.3 W/OMC drive "thumb"

Unless someone did a very strange swap, you have a GM 4.3 engine with OMC controls, wiring and other customizations, and an OMC Cobra drive (Made by OMC).

When was the last time your lower/transom shift cable was replaced or adjusted? It sounds like it may be jumping out of gear. If it hasn't been adjusted in the last 2 years, it needs it. If it continues to jump out of gear you will trash your upper drive. A new cable is only $75.

You need to pull the drive and use an OEM service manual to do it properly.

 

[haliburton Lk]

Re: 1989 4.3 W/OMC drive "thumb"

if it jumps out of gear does it pop back in? the thump that I feel (no grind or noise) is just that a thump, like I hit something in the water...thanks

 

[danond]

Re: 1989 4.3 W/OMC drive "thumb"

I have no idea, I'm assuming it would, but I would suggest you check your transom shift cable. Aside from lack of gear lube, it's why Cobra outdrives fail.

 

[bruceb58]

Re: 1989 4.3 W/OMC drive "thumb"

You better check your lower shift cable but I am afraid it may be too late for your lower gears. That thump is the dog clutch disengaging and the engaging again. Don't drive the boat anymore until you check out your cable. My very first OMC Cobra did the same thing when I first bought it. Dog clutch was toast.

 

[Gary H NC]

Re: 1989 4.3 W/OMC drive "thumb"

This is critical....the REAL manual is the only one that steps you through the exact adjustments with pictures..
The Seloc and Clymers manuals do not.

Email the seller,Tell him Gary in NC sent you.Ask if he has one that is in more of a used condition for less money.

http://cgi.ebay.com/ebaymotors/1988...NUAL-RARE_W0QQitemZ200345448892QQcmdZViewItem

 

[haliburton Lk]

Re: 1989 4.3 W/OMC drive "thumb"

You better check your lower shift cable but I am afraid it may be too late for your lower gears. That thump is the dog clutch disengaging and the engaging again. Don't drive the boat anymore until you check out your cable. My very first OMC Cobra did the same thing when I first bought it. Dog clutch was toast.

Did yours do it all the time? mine can go a whole day and not do it

 

[bruceb58]

Re: 1989 4.3 W/OMC drive "thumb"

Mine did it often. You may be ok then. Definitely need to look at the cable to see if it is still ok and definitely check its adjustment.

 

[haliburton Lk]

Re: 1989 4.3 W/OMC drive "thumb"

Thanks Bruce58,

 

[Gary H NC]

Re: 1989 4.3 W/OMC drive "thumb"

Do NOT attempt to adjust the cable without the manual...I can't stress that enough.
Many gear sets have been destroyed by people adjusting it without the book.
The price of the manual and cable is WAY less than the gears being replaced.

A couple hundred verses a couple thousand....the choice is clear..

 

[haliburton Lk]

Re: 1989 4.3 W/OMC drive "thumb"

Ok thanks to all