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 Post subject: 80-81 Mercury 25
PostPosted: 17 Dec 2017, 16:13 

Joined: 25 Oct 2017, 18:48
Posts: 9
Hey Guys, Just got my new to me Merc running fairly well, at least in the test can.
I replaced the impeller, rebuilt the carb and fuel pump. New fuel bulb and quick connects
for fuel line. I got it so it fires on one pull yea! Smokes a bit much maybe due to rich oil?
My service manual says fuel to oil, 12oz to 5 Gallons, or 2.4 oz /gallon. 50:1
50:1 is I believe is really 2.56oz/ gallon. My bottle of Merc oil says mix 3oz/ Gallon for 50:1
I mixed 3oz / Gallon at the because I just read the bottle. No problem remixing but do you
guys think that much more oil would make the motor smoke that much more? Oh, 119psi in
both cylinders. Maybe I just need to run it under a load, but lakes are all frozen here now. :(

Second question, There are two bleed hoses, very small diameter hoses that run from the
cylinder block to the reed block connecting to two very small brass barbed nipples at the base. They
seem fairly tight when placed over nipples but either get blown off or vibrated off very soon
after the motor is running. I cannot find out what these are for, it seams that the motor runs the same
if they are connected or not. Thank guys!


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 Post subject: 80-81 Mercury 25
PostPosted: 17 Dec 2017, 19:05 

Joined: 13 Nov 2014, 08:01
Posts: 589
It will smoke less when it is hot. Not enough load in test tank to get hot. It's good to go on that front.

A little extra oil is not a problem for engine.


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 Post subject: 80-81 Mercury 25
PostPosted: 17 Dec 2017, 21:33 

Joined: 04 Feb 2013, 22:11
Posts: 267
Get the tygon tubing from a small engine shop and replace those hoses. They should be a real PITA to fit over those barbed fittings. Most likely the hoses have gotten harder and gained a memory. You can also get a GOOD grade of tyrap and cinch them down with them on the fitting. Take a regular pair of pliers and grasp them and roll the pliers down and that cinches them super tight. Most new motors use them instead of clamps now.


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 Post subject: 80-81 Mercury 25
PostPosted: 18 Dec 2017, 15:55 

Joined: 25 Oct 2017, 18:48
Posts: 9
Thank you for your replies CRS and nccat, I zip tied the hoses and they are on tight.
I still have the question as to what is the function of the bleed hoses? Are they sending unburned fuel back to the
reed block or vice versa?


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 Post subject: 80-81 Mercury 25
PostPosted: 19 Dec 2017, 10:43 
Donor
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Joined: 15 May 2010, 00:38
Posts: 2400
Location: Central Florida
In all of the two stroke engines fuel tends to puddle in places such as the lower main bearing. A bleed hole/nipple is placed in these areas to pull the excess fuel away and put it back into the induction system to be burned.
As far as too much oil goes? You can run that engine with double the normal oil ratio with very little smoke, If you are typically going to run the engine hard or in weedy areas extra oil can be your friend.


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 Post subject: 80-81 Mercury 25
PostPosted: 19 Dec 2017, 19:07 

Joined: 25 Oct 2017, 18:48
Posts: 9
Thank you Pappy, I was hoping you would chime in as your knowledge is invaluable!
The previous owner had obviously run the motor for quite a while with those two little hoses
unattached as there was quite a bit of goo around the bottom of motor and lower cowl.
Looks like I'm good to go as far as the motor goes. Maybe a little paint and new decals.


1980 Mercury.jpg
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 Post subject: 80-81 Mercury 25
PostPosted: 19 Dec 2017, 21:16 
Donor
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Joined: 15 May 2010, 00:38
Posts: 2400
Location: Central Florida
Keep close tabs on the gearcase oil on that one. That vintage had a bit of a tendency to have a shorter than "normal" gearcase life.


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 Post subject: 80-81 Mercury 25
PostPosted: 20 Dec 2017, 22:29 

Joined: 25 Oct 2017, 18:48
Posts: 9
Thanks Pappy, will do. I have already changed gear oil twice, once when I got it, once when i
did the impeller. Oil looked ok the first time. I appreciate the comments!


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