Mark 55 won’t shift after impeller change

[John Gleason]

Hi,

New to the forum, boar ownership, and antique outboards.

I have a Mark 55 that I’m getting ready for it’s first season in a while.  The water pump impeller has been changed (took to the shop last fall because I couldn’t get the cover off), but since I put it back together the motor won’t shift gears…it seems to always be in forward (was working before the new impeller).  I took the lower unit off again and tried following the manual.  The only thing I noticed is the shift shaft cover being oriented differently than the manual.  Any advice on what I might be doing wrong?

 

Any tricks to get the lower unit back on?  It was a pain to install last time.

[Sam M.]

I am not knowledgeable about Mercury outboards, but the following should hopefully apply anyway:

When putting the lower unit back in, be sure the gearbox is in the same gear as the gear shift lever BEFORE the gearbox even approaches the rest of the motor.  Trying to do gear shifting so all the linkages line up while holding a lower unit is not easy.

Start by getting a flashlight, looking up into what used to be the darkness, and figuring out where the to aim the driveshaft.  Then lift the lower unit up with the shaft aimed in that direction.  Also, do all of this with the motor securely locked in it’s tilted up position.  Next, line up the water tubes, push the lower unit in a little more so the tubes go together, and then keep an eye on them as they will likely be interested in falling out of place.  Finally, push the lower unit in as far in as it will go, then discover there is still a gap, and it won’t go further (unless you are particularly lucky, or the motor likes you, and it will all go into place without further fuss).  What you do about this gap, is have the person you smartly asked to help you (before you started lining things up) slowly pull on the recoil starter until the splines from the powerhead line up with the splines of the lower unit’s driveshaft in a somewhat startling manner, as the lower unit you are lightly pressuring upward will race into place.  Next, it’s time to hope that the bolts that hold the lower unit on aren’t out of arm’s reach, and if they are, it’s time to hope your helper hasn’t given up on you and gone out of hearing range.

 

You say you’re new to old outboards, so here are a few more tips, not exactly related to what you’re asking for, but that I hope you’ll find helpful anyway:

When running the motor in a barrel (or even on a boat), be sure the water level is higher up than the impeller before starting the motor.  This will help prevent the water pump impeller from wearing out prematurely.

At the start of the boating season, it’s a good idea to replace (or at least check on) the gearbox oil.

While I don’t know the fuel mix ratio for this Mercury, it will quite likely require a lot more oil in the fuel for proper lubrication than newer two-stroke outboards.  The correct mix ratio is definitely something to check before running it.  The correct ratio might be 16/1 but that is only a guess, and TC-W3 rated oil is the kind to get.

Hope this helps!

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seakaye12

[dave-bernard]

Call me  914 310 7086 Dave

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Tubs

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