Mariner 115 lower Unit Questions

J

jp2570

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I believe it is a 1987 motor that has had the original lower unit replaced with a used one off a 75 hp mariner at some point.

I was on the lake and the motor made loud clanging noises and locked up--even in nuetral. Returned to dock with trolling motor. Started the next day with muffs---same noise/problem.

I removed the lower unit and I can't turn the propeller in either direction. How freely should it turn? The splines on the upper part of the drive shaft look fine. How likely is it that the lower part of the powerhead is damaged? I "briefly"-- 2-3 seconds-- started the motor without the LU on it and it sounded great. Do you think this is limited to the LU or do I have additional problems?
 
redjmp

redjmp

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Re: Mariner 115 lower Unit Questions

If the spines on the drive shaft are fine, then the powerhead should be fine as well.
Did this used unit shift and run well before it locked up or is this the first time you tried it out?
 
J

jp2570

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Re: Mariner 115 lower Unit Questions

The motor ran and shifted very well since I bought it last June. Recently I thought I heard a rattle or something the last couple of times I had the boat out. Yesterday, it started as usual, but as I was heading down the lake at about 27mph, it made a loud clang, started to sputter and the stopped. I tried once to start it back but it seemed locked up. i jiggled the flywheel back and forth and it started, but clanged, shuddered and stopped.

Today I removed the lower unit, but I can barely get the drive shaft to move. I had just changed the LU fluid the day before. Today when I drained it I did not see water, but it had metal in it and it did not seem like very much fluid drained out.

Should I be able to turn the prop/drive shaft by hand with the LU removed?
 
C

carholme

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Re: Mariner 115 lower Unit Questions

If the last gear it was in was Forward then the prop should act as follows:

Using finger pressure on the prop only,

Forward: Prop will turn (ratchet) CW but will not turn CCW
Neut: Prop will turn in either direction freely
Reverse: Prop will not turn in either direction.

But it sounds like you have a lockup in the LU and if it was mine, I would be tearing it apart to see what damage is done. Do you have the manual and the parts lists? If not post your s/n.

Gerry
 
J

jp2570

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Re: Mariner 115 lower Unit Questions

Thanks for the info guys. I have a downloaded manual, but it seems a little hard to follow at times. Can the LU be rebuilt at home with common tools, or does it have to professionally repaired? Are there rebuild kits available? Do you mean the serial number for the engine or the lower unit specifically?
 
J

jp2570

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Re: Mariner 115 lower Unit Questions

Gerry,

Turning the drive shaft in either direction produces a grind. The prop or drive shaft will not move in either direction smoothly. In fact it takes a good effort to get it to turn.

However, before I removed the lower unit, the prop would turn in neutral, but it felt and sounded rough.
 
C

carholme

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Re: Mariner 115 lower Unit Questions

The reason I ask for the s/n is most people believe what they read on their title papers as far as the year of manufacture is concerned, By producing the s/n of the engine, we can check the year and this ensures that we get the right manuals and especially the correct parts lists.

What manual do you have as removing the bearing carrier is pretty straightforward and for the moment, that is what you need to get out to see where the damage is. The only special tool you need is to remove the cover nut to get the carrier out. The cover nut is item 70 in this link:


http://www.crowleymarine.com/mercury-outboard/parts/278_23.cfm

and you should be able to see it when you look in, in front of the prop. The tool is slotted to fit the slots in the nut and you can make one out of a piece of pipe if you are mechanically inclined. If not, your local dealer may lend/rent you one for the day.

Gerry
 
J

jp2570

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Re: Mariner 115 lower Unit Questions

Gerry,

Here is a pic of the SN label. It is hard to make out. I increased the contrast and brightness a lot just to see it. What do you think.IMG_03702.JPG
 
Faztbullet

Faztbullet

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Re: Mariner 115 lower Unit Questions

Can the LU be rebuilt at home with common tools, or does it have to professionally repaired? Are there rebuild kits available?
Click to expand...
It will be a whole lot cheaper and quicker to get a good used one to replace it and make sure its a 2:1 ratio. You will need several special tools to do this at home and the parts are outrageous and no one offers aftermarket gears for these that I know of.
 
J

jp2570

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Jun 11, 2011
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Re: Mariner 115 lower Unit Questions

I am going to open it up today and take a peek. If it is really bad, what can I expect to pay for a used one and how do I know what will fit and work on my motor? Are there various LU that will work. What do I look for when shopping?

Also, I am in Harlan, KY and we do not have any local marine shops.
 
J

jp2570

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Jun 11, 2011
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Re: Mariner 115 lower Unit Questions

Well, I just opened it up and it is ugly. The end of the drive shaft is ground up and there are a few teeth broken on the gears that I can see. I can only imagine what else is behind there. Metal pieces were loose in there and 3-4 ball bearing came out as well. I guess I am in the market for a LU......................
 
Faztbullet

Faztbullet

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Re: Mariner 115 lower Unit Questions

A little ways down the road from ya in Scottsville...
Marine Parts Warehouse Inc
4488 New Glasgow Rd
Scottsville KY 42164
270-618-5200
 
redjmp

redjmp

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Re: Mariner 115 lower Unit Questions

Theres lots of these on fleabay rather cheap...
 
J

jp2570

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Jun 11, 2011
Messages
19
Re: Mariner 115 lower Unit Questions

Thanks for all the input guys.

I put another lower unit on the motor that I purchased from a marine dealer. It is a 2.1 ratio and is off a mariner 115.

Question.......The previous lower unit was off a Mariner 75 and was on there when I got the boat. Does anyone know what the ratio of that unit would have been? My manual says the 75 hp LU was 2.3-1. It seems that I have lost power and the good hole shot that I had before. With a 2.1, what prop should I have? The one on there is SS says 21P.
 
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