Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc Thu

[y2jericho]

My mercury 1970 650cc Thunderbolt 4 cylinder will go into reverse on land when i was checking the gears with muffs on but it won't go into reverse on the water. Its running at about 1400rpm on land because of no pressure and about 900 on the water<br /><br />What should it be set to on the water would 1000 be to high?<br /><br />It makes a grunting/crunching noise when trying to put it into reverse on water. And when i rev it up it still makes the noise.. Both my lowerunits do this although i don't have the older LU as it was scrap metal.. The new one is near new doing only 4-5 hours on it since complete overhaul<br /><br />Thanks guys

 

[steelespike]

Re: Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc

Re: Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc

I dont know your motor But I believe there is a specific procedure to properly install shift linkage and lower unit. Someone may be along with specifics.But in the mean time try to find a ser. manual.Also you could adk at Johns old mercury web site www.pfs-ware.com look for the forum.<br /> also some very good links.

 

[Yepblaze]

Re: Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc

Re: Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc

Check the lower unit oil just because.<br /><br />Could it be a prop hub only breaking free in reverse?<br /><br />Could be shift cable out of adjustment?<br /> <br />Worn, loose, or bad shift linkage, or controller?<br /><br />Further attention needed inside lower unit? <br />Not shimmed correctly or retainer loose?

 

[y2jericho]

Re: Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc

Re: Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc

Oil seems to be fine.. I just replaced it and as soon as i took it out it was a dark yellow/hazle colour but thick because it was aerated<br /><br />Basically it was fine..<br /><br />The hub is fine because it has been doing this with 3 different propellars all with fine hubs<br /><br />.. It could be its not installed properly but this doesn't explain why it enables on land but in water the motor turns something to making that clicking/thumping sound but it doesn't want to enable into reverse in the water...<br /><br />My revs are at 600-700rpm in the water currently as it is the lowest i can set it without the motor revs jumping around alot and wihtout it dieing..<br /><br />This is a 115hp LU from the same era with a compensated prop to match the revs

 

[y2jericho]

Re: Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc

Re: Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc

Just thinking maybe the waters pressure has something to do with it.. In the air it moves much easier and takes less force.. In the water its got to displace the water.. Just wondering<br /><br />Wierd

 

[Chinewalker]

Re: Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc

Re: Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc

Disconnect your shift cable in the water. Make sure boat is securely tied to dock. Operate the shift linkage inside the belly pan by hand (all the way back is reverse). If the motor shifts properly, you have a linkage adjustment issue. The in/out of water thing doesn't have anything to do with it. I'd bet that if you put some resistance on the prop on land it would make the same grinding noise... Just don't use your hand to add the resistance...<br />- Scott

 

[sethjon]

Re: Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc Thu

My mercury 1970 650cc Thunderbolt 4 cylinder will go into reverse on land when i was checking the gears with muffs on but it won't go into reverse on the water. Its running at about 1400rpm on land because of no pressure and about 900 on the water<br /><br />What should it be set to on the water would 1000 be to high?<br /><br />It makes a grunting/crunching noise when trying to put it into reverse on water. And when i rev it up it still makes the noise.. Both my lowerunits do this although i don't have the older LU as it was scrap metal.. The new one is near new doing only 4-5 hours on it since complete overhaul<br /><br />Thanks guys

What OD do you have? It sounds like its electrical rather than the cable. What it does is actually shut the motor off for a split second and once the shift is made it turns back on. Do you ahve an OMC OD?

 

[CharlieB]

Re: Goes into reverse on land but not into reverse on water.. Mercury 1970 650cc Thu

You can also check the shifting on the trailer with the motor OFF and the lanyard pulled, while turning the prop by hand have a helper shift the Control into Reverse.

Now STAND on an ear of the prop trying to turn the prop CW, does it slip? If fully locked it should turn the motor. Note: Wear sturdy shoes, no flip-flops.

Disconnect the shift cable and manually shift into Reverse and repeat the turn test. Also, did the linkage move any farther than it did with the control attatched? If so, replace the cable and repeat the turn test.