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1963 mercury 9.8 runs good then shuts off. Why?

tgeers

tgeers

Member
It is easy to start, idles good responds to a full throttle when in gear. But periodically it will just shut off. I noticed that the bulb coming from the fuel tank will have little fuel in it, and when I pump it a few times the motor will start right up. To my untrained knowledge of outboards, I'm thinking the fuel pump is not strong enough to pull fuel into the motor when wide open. I'd appreciate any opinions you could share with me.
Thank you
tgeers
 
Yes....good guess. Also might test it by raising fuel tank to a higher level and see if it's able to pump the fuel better with less lift. The screen could need to be cleaned inside the fuel tank too. Make sure no problem with the squeeze bulb too. If it's a plastic tank make sure it's venting properly and the lift tube is sealing well where it's fastened to the tank fixture there inside the tank.....I have seen many of them sucking air at this connection inside the tank.
 
Right. The fuel pumps on some of these early, small Mercs were too weak to operate the motor after it aged a bit. I've swapped many of them out for aftermarket pumps to solve that tissue. Shortening the fuel hose as much as possible, and raising the tank, will help.

Jeff
 
I will try raising the fuel tank. Also, I have tried using several different aftermarket 3/8" fuel lines. Do you think it would be better to use a smaller diameter line to reduce the volume of fuel being pulled through the line? It would be more in keeping with the size of the fuel line inside the motor.
Thank you for your replies
tgeers
 
?----A larger fuel line would help !----Test run with another hose and tank.----Or inspect pick-up hose INSIDE the tank.
 
Thank you guys for your suggestions. I'm going to try them out next week when it's a bit warmer on the Ohio river. Hopefully your suggestions will do the trick. I'll report back.
Thank you all again
tgeers
 
I took everyone's advise by raising the fuel tank, shortening the fuel line, and I also added some Seafoam to my fuel. After several hours of off and on running while fishing, the same problem of cutting off occurred. Then late in the evening the motor bogged down for a few moments and then quickly accelerated and continued to run as it should. I attributed this to possibly the Seafoam breaking through some blockage allowing the fuel to finally flow freely. Before this occurred, I did check the spark plugs, and there were definite signs that the motor has been running lean. Fastjeff, you suggested that the fuel pumps were weak. Does this sound like a possible fuel pump issue? If so, would you recommend a repair kit or new pump? If a new pump is your recommendation, what pump would you suggest? Thank you again for your help. tgeers
 
Wow....your a "night owl". A kit will maybe do the trick. If it's not available here, try Tim's Outboard in Hackensack MN 218 682 2331, talk with Mike, Dan, or Teresa. Have model # ready. I really wouldn't trust that old pump, besides...the diaphragm might have been softened and/or deteriorated by exposure to ethanol fuel. Here in MN, where ethanol is mandated, fully 1/2 of all my repairs......are fuel related......also, these plastic fuel tanks are really shortlived and often cheaply made. They fail from too much exposure to the elements. The plastic fixtures on top, whether it's a fuel level gauge, or fill cap base, or fuel line outlet fixture, crack and often leak water into the fuel. The ethanol fuel will suspend water with the equivalent weight of the ethanol. The motor can burn up that mixture, but if the fuel sits for any length of time, the mixture of ethanol/water will separate. Then it cannot be remixed. This is called "phase separation". This "mixture" will settle to the bottom of the fuel tank, often getting sucked in to the motor, causing big trouble. If the "petrol" part of the mixture gets sucked into the motor instead, then we have a greatly reduced octane content. This also can severely damage the motor.....especially electronically controlled motors. The automatic vent systems on these plastic tanks are also quite problematic.
 
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Hi Guys,
Things aren’t getting better. I am asking you to kindly help me with several questions. By way of background, let me explain the context in which my motor is involved. First, I am a 77 year old “cat fisherman” from Southern western Ohio. I fish the Ohio river and its tributaries mostly in Indiana. I have a small 10 foot customized jon boat. Check my avatar. The customization was done with aluminum, so I do not believe it to be very heavy. I estimate the total weight, with me in it, to be about 500 pounds. On calm water, the best speed is about 6.5 mph. That is far less than I had hoped. .
The motor will run fine, then without a warning will die. It will start right up and run for a few minutes then die. There are times when it will run for long periods without a problem, except for what I feel is a lack of power. The motor will sputter, worse a low rpms. The spark plugs are looking like it is running lean. If I were fishing in my garbage can, the motor would run all day without a problem. But on my boat, it’s a different issue.
We have determined the problem could be in the fuel pump. I am familiar with Evinrude motors, but this is the first Mercury. Much of it, I don’t even recognize. My service manual is not much help because it covers many different years and size motors, nothing specific to my motor. I do know I have a 1963 9.8 110 motor with a tillotson carb with attached round part with a screen inside. I couldn’t find a number on it. First question, is that the fuel pump as part of the carb? Question two, The fuel line comes into the motor through, what I thought a rectangular fitting that is attached to the engine block. There is no number that I can see. Is that the fuel pump? Question three, Before I can order any parts, I need help in identifying what I need. Can you help me do that? Question four, my mph seems very low. With a repaired fuel system, do you think I can get 10mph or better from this motor? If not, I may have to find another motor to use. I must be fast enough to out-run the barges on the Ohio.
You have been very helpful to me and others on this forum. I am in new territory here and your help is greatly appreciated.
 
If this is a 1963 motor you'll find the serial Nr. on a plate between the clamps, a 1963 motor will be white if it's black it will be later.
1963-9.8.jpgIf you post an image (not larger that 200kb) of the cowling we will have a better idea.
 
Sounds like it might be running on 1 cylinder.----Post compression numbers.----Test for spark.----Spark MUST jump a gap of 1/4" or more.----Have you installed a new water pump impeller ?----Test run with another tank and hose ?
 
Sorry about not putting in the serial number before. 1637259 is the number. It looks like the picture you posted except mine is black. I took some pictures but have not been able to post them. I'll figure it out later. Here is my plan, I've checked the spark and it is good for both cylinders. The spark plugs look like the originals so I will replace them. I will check the compression on Monday. By turning the flywheel by hand the resistance seems to be equal when reaching TDC on each cylinder. I will try with a metal fuel tank. The impeller has been changed. Can't get back on the water until Monday. If I'm missing something to try let me know. Meanwhile, I will try and get my pictures put online. Can I post a video of the motor running. If not, I could post a vid on YouTube if you think it would help.
Thanks guys.
 
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Ok that is a 1964 model - have you rebuilt the fuel pump? The proper plug is Champion J7C the gap is .025", the points are set @ .020, the carb should be checked for float height and damage that will make it sink.Carburetors.jpg
 
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Is it possible from these pictures to identify what kind of repair kits I might need?
I will first try new spark plugs and a compression test. But if that doesn't help, I may have to dig into the fuel supply system. I've successfully done that before with Evinrude motors, but this is foreign territory for me. I appreciate your continued interest in my situation.
 
Item in first picture is the fuel pump.----Works on pressure pulses from crankcase.----Might be running on 1 cylinder.---Do both sparkplugs look the same ? ----Does the spark jump a gap of 1/4" ( 6 mm ) , yes or no ?
 
The spark plug shows it is overheating which may cause shutdown see chart, are you using the right plug as I posted earlier?
spark-plugs.jpgWhen the motor stops does it die slowly or stop instantly?
What type of fuel tank are you using, a Mercury tank will have a fine mesh screen at the end of the pick up tube inside the tank; crap may be floating around and plug it.
 
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Guys, I just purchased a compression tester from Harbor Freight. I figure its good for at least one use. Unfortunately my compression readings were only 62psi in each cylinder. That seems very low to me. I followed the instructions with the tester to warm up the engine then remove the spark plugs and crank the engine at least 8 times. My Seloc service manual does not give a specific value for compression, but did say it was important that the numbers be very close for each cylinder, which they were. If these numbers are too low, does that mean this motor is junk?
 
There is a wee plate ( 3 screws I think ) on the side of the block.---Allows you to look at pistons and rings.---Before you ask , no it can not be a blown head gasket.---There is no head gasket.
 
If the compression numbers are too low, then would it follow that the pulse from the engine block to the fuel pump would be decreased? If that is the case, then would that mean the fuel pump is possibly OK but not being given a strong enough pulse to make it run correctly?
 
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I am running 50:1 10w 40 oil.
Above are pictures of the cylinder rings. Hope you can make them out. Let me know what you see.
 
That oil could be the problem if it's for autos, you have to use 2 cycle TC-W3 oil - if you want to bring back the compression I would recommend Amsoil HP marine at 50:1. The rings look OK but the Nr. 1 piston looks cruddy, when you put that intake deflector back on you should use a new gasket or sealer on it.
 
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I appreciate all the help everyone has given me. I can and will do everything that has been suggested, including using different oil. I've only had this motor for a few months, so I don't know anything about it's history. The question remains, what should I do to make this motor run properly? Do I rebuild the fuel pump? Do I use a different fuel storage container? Would you recommend junking this motor and purchasing something newer?
Hopefully I will not need to continue this thread for much longer, but I am looking forward to receiving your final recommendations.
Again, thank you so much for your help.
 
My opinion.------A motor that is 60 years old requires new seals on the crankshaft.-----New seals on gearbox.----All easy to do.------Then it will run for many more years and you will get a lot of compliments.-----But for most folks a new motor is the best way to go.
 
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