Mark 55 Idles Great, Very Rough in Gear

Mercury Outboard  general discussion

Mark 55 Idles Great, Very Rough in Gear

Postby amreame » Mon May 27, 2019 4:48 am

I have a 1957 Mark 55E and the end of last year I switched out the prop for my last trip on the lake. I'm not sure what I missed when I put the new prop on but when I launched at the lake and put it in gear the motor sounded very rough. Previously, with the other prop on, it was perfect. After about 2 minutes idling away from the launch I went to give it some gas and it sounded much worse and then sounded like it was going to quit. Increasing the throttle gave no power to the motor. Returning to neutral and it sounded good again. Long story short, a minute or so later the prop fell off. Luckily the water was warm and I swam her to shore.

This spring I purchased a new prop along with cone nut, prop washer tab, and the spline spacer (I did not purchase a spacer washer for behind the prop if that's relevant). I have the motor on an Alumacraft FD and went to run it today and the same thing. Idles awesome but when I put it in gear it sounds terrible. Reverse also sounds bad. Now that I'm typing this I realized I haven't checked the lower unit oil yet. I'll check tomorrow but does anyone have any ideas on this? I'm assuming it's time to take the lower unit apart and see what's going on. With the boat out of the water and the motor in neutral, the prop spins freely but when I shift it into gear the prop spins in the correct direction but not smoothly.

I've done lower unit rebuilds on mid/late 50's Evinrudes but haven't had any experience with Mercs. I do have the maintenance booklet and a parts catalog for this motor. Any tips would be appreciated!
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Re: Mark 55 Idles Great, Very Rough in Gear

Postby 58woody » Mon May 27, 2019 2:04 pm

The thick splined spacer must be installed first on the prop shaft. Your prop might be binding on the prop shaft cover nut (it has the 4 holes). If you take the prop off check to see if that is happening.

Then report back.
Mark 6, 1956 Mark 55 & 55E, 1959 Mark 55A, 1958 Mark 58, 1960 Merc 300, 1961 Merc 500, 1961 Merc 700, 1964 Merc 1000 Bradford, Ontario, Canada

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Re: Mark 55 Idles Great, Very Rough in Gear

Postby Pondrocket » Mon May 27, 2019 3:40 pm

First things first What condition is the complete motor in?  Is this a motor you've had for years that was running before or is it a purchase in the last year or so and you never ran it yet? If as you say you never changed the lower unit oil yet and by the sounds of your reply, lower unit needs to be inspected and rebuilt. Keep us posted as Chris mentions with pictures and we'll give advise from there...
Mark30e,57'Mark55e,3-Mark58s's,Mark78ael,twin 64'Merc 650's Classic Mercs Keep em Alive! https://waterhogsworks.com/
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Re: Mark 55 Idles Great, Very Rough in Gear

Postby mercules » Mon May 27, 2019 6:41 pm

Look in the parts list for the splined thrust washer that goes on the back of the prop, as 58woody said it has to be installed. Don't tear down the LU yet.
Let's fix it now - before we launch the boat.
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Re: Mark 55 Idles Great, Very Rough in Gear

Postby Michael » Mon May 27, 2019 7:17 pm

I agree with 58woody check for proper assembly first.

you can also remove the prop and rotate the prop shaft to feel and listen for unwanted friction or grinding, if it spins smoothly fire it up in a trash can/test tank .......if you feel or hear bad things its tear down for inspection time
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Re: Mark 55 Idles Great, Very Rough in Gear

Postby amreame » Mon May 27, 2019 9:00 pm

Thanks for all the replies, I appreciate it. To answer the first question, I purchased this motor last spring and ran it a good 20 times last year, some days I was out on the water all day. It had been recently serviced before I purchased it and I never had any issues.

I went to look at the motor this morning and took some videos (with sound) and pictures.

Video of spinning the prop in neutral: https://vimeo.com/338725759
Video spinning the prop in forward: https://vimeo.com/338721008

When I put it in reverse I could hear some noises in the mid shaft and the prop was very hard to turn. When I had it in the water yesterday I was able engage reverse and it did function.  

Is this the splined washer for the back of the prop? https://www.ebay.com/itm/401757216369?_ ... .S1.R1.TR3 . I do have one of these between the prop and the washer tab.

I didn't drain all of the lower unit oil but I didn't see any metal shavings for what came out (oil pan was full). Depending on what I need to do here I'll drain the rest and replace.

Attached images: Lower unit with prop, prop parts, naked lower, oil.

Based on the noise it made when turning the prop by hand when sifted in reverse, I'm assuming it's time to dig into thing a bit deeper. What would you guys recommend? I thought I had the correct tool to remove the gear housing cover but my tool is a little small, so I'll have to grab one the correct size.
Attachments
20190527_131957.jpg
Naked Lower
20190527_131940.jpg
Prop Parts
20190527_130817.jpg
Gear Oil
20190527_130250.jpg
Lower Unit
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Re: Mark 55 Idles Great, Very Rough in Gear

Postby 58woody » Mon May 27, 2019 9:17 pm

It looks like some wear on the cover nut from the back of the prop, hard to tell in the pic but sure looks like it.
I really think that is the problem.

The clicking sound is normal, now pull the motor over in forward with the rope and you will not hear that sound. The sound by turning the prop is just the clutch teeth clicking on the gear. 100% normal.

The thick washer goes on first, then the prop, then the tab washer, then the thin splined washer and finally the prop cone.

You can not shift into reverse unless the motor is running.
Mark 6, 1956 Mark 55 & 55E, 1959 Mark 55A, 1958 Mark 58, 1960 Merc 300, 1961 Merc 500, 1961 Merc 700, 1964 Merc 1000 Bradford, Ontario, Canada

Member of the AOMCI Upper Canada Chapter http://uppercanadachapteroftheaomci.yolasite.com/
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Re: Mark 55 Idles Great, Very Rough in Gear

Postby ctpdsr » Mon May 27, 2019 9:31 pm

Photo of thick washer on shaft. Did you remove this with the old prop?

Chuck

IMG_3191.JPG
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Re: Mark 55 Idles Great, Very Rough in Gear

Postby amreame » Mon May 27, 2019 10:07 pm

Thanks 58woody, Glad to hear the clicking is normal! Thank you for the prop assembly procedure as well. I just ordered some of the thin and a few of the thick spline washers. Here's a high def image of the lower without the prop: https://i.imgur.com/p6R73Qh.jpg There is definitely some wear there. I'll replace that just to be safe. Can you tell me the name of the tool needed to remove that? Is there anything else I should replace or look at with that removed?

Chuck, I honestly can't remember. I would have thought I'd only switched the prop and left the other items on but I was in a rush to get loaded up and might have forgotten to put it back on. I have some parts on order though and grabbed a few extras as well.
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Re: Mark 55 Idles Great, Very Rough in Gear

Postby dave bernard » Mon May 27, 2019 10:42 pm

No need to replace that. do it if you ever have the lower apart. in my opinion the assembly is as follows thick splined washer, prop, thin splined washer, then the tab washer, then prop nut  very tight then bend all the tabs. the reason for the thin washer is to allow to put a screwdriver under the tab washer. it also allows the tab washer to be bent in the slots better. more secure. just saying.
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Re: Mark 55 Idles Great, Very Rough in Gear

Postby mercules » Mon May 27, 2019 11:09 pm

How are you turning it in reverse - by the prop?
Any resistance will be from the powerhead and/or the waterpump impeller this means you might have flipped some blades, I'd check it.
http://www.johnsmcintoshvintagemercuryo ... 04Cyl.html
I would also undo the gearcase cover and put some anti-corrosion grease on the threads then tork it tight, do the same for the waterpump cover so you'll be able to undo it when it comes time to change it.
Lube-intervalssmall.jpg
Let's fix it now - before we launch the boat.
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