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Old 17 August 2013, 13:57   #1
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80's Merc 135Hp Outboard Help

Hi Guys my Mid 80's Mercury was a pain after last winter but after finding a split pipe going to the fuel filter it ran sweet until it was in the water, she wouldn't rev to about 4000rpm that's all and after 2 minutes of run time the alarm would sound been oil or over heating,

Ok I've just had chance to look over the engine and found a small pipe from the main fuel in to the oil pump with small splits in it at both ends, could anyone tell me what effect this pipe would have on the oil or fuel system if it was leaking.. Thanks Guys

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Old 17 August 2013, 14:04   #2
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After looking at he photo myself again, I take it the more throttle the more that pump puts oil down the broken pipe into fuel mix? so if this pipe was broken or leaking the carbs would be getting no oil causing my oil or more like over heating alarm?
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Old 17 August 2013, 14:44   #3
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For a mid 80's engine I'd expect the oil sensor wasnt that sophisticated so probaby just an oil level alarm.
So more likely you are getting an over heating alarm. If you ran it with that pipe off completely I'd expect you to seize the engine pretty quick? But I'd also expect there to be oil all over your engine so I assume its not been leaking while underway. Or if it was its been letting air in rather than allowing liquid out? At full pelt could the fuel pressure be enough to suck on the tube and draw in air through a crack too small to leak viscous oil out...?
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Old 17 August 2013, 15:19   #4
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Thanks, yeah I think it would be too small to leak oil out, and no oil from what I can remember was leaked around the motor..

I don't have a clue how the oil system works but If remove all the plugs and turn the motor over at speed on full throttle should I get some oil dripping out or does it use pressure from the motor :s Thanks again
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Old 17 August 2013, 16:00   #5
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1986 Mercury Marine Mercury Outboard 1135746 OIL INJECTION COMPONENTS Diagram and Parts

AFAIK the engine is passing a mechanical action from the engine to the pump rather than suction.

The amount will be very small though! Remember that it's 50:1 so for every 1ml of fuel pulled through you'd only pull through 20microlitres which is about 1 drop! You probably can't even get the tick over speed for more than a few seconds by hand - say thats 600rpm thats ~10 rps. Simply turning it by hand rather than trying to start it would be more like 1rps! At 600rpm a (modern) outboard your size would drink between 0.2 and 0.5gph - lets call that 2litres an hour. So if you turned it over at 600RPM for an hour you would expect to pull through 40ml of oil if the mix is right. But as I suspect you can't maintain that RPM so more like 4ml in an hour which means in 5 minutes you'd only pull through 0.2ml of oil. Thats not a lot!! Having the throttle open might help because you might make the oil delivery think that it was drinking 40-60litres an hour of fuel at 5500 rpm so 330,000 revs an hour. Thas 0.18ml per revolution, so 0.003ml of oil (less than a drop). If you could muster the energy to turn it over at WOT for 5 minutes you'd maybe pull through a ml of oil?

Get what I'm saying - not big volumes and manually turning it over might not bring much through...

IF you ran the engine on 50:1 from the tank with the oil pump output disconnected from the fuel and dripping into a suitable dish. You'd need to seal off the pipe or you will get air in the fuel. You'd then be able to pull it up to real revs?

But do you think the pump is not pumping or just that the nipple to attach the pipe to is broken?
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Old 18 August 2013, 07:38   #6
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thats the oil pipe that goes to the fuel pipe, there should be NO air visible in that pipe, if there is it will require bleeding
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Old 05 September 2013, 18:31   #7
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Bit late, but I've only just seen this.
The big pipe to the upper left of your pic is the feed pipe to the oil pump from the oil reservoir on top of the engine.
The small pipe - the broken one - links the oil outlet from the pump to the 3 way brass connector. Fuel enters this connector from the inlet at the front of the engine, picks up the oil then flows out from the other side of the 3-way to the carbs.
If the small pipe is broken you are getting no oil into the fuel & thus no lubrication to the engine. Result likely to be a damaged or seized engine.
I had this pipe split at its lower end on my own engine - 1989 Black Max V6 135hp - 3 weeks ago. Fortunately I spotted it (lots of oil on the bottom of the port shell) & replaced it - 4.5mm i/d - and don't appear to have had any problems.
The manual says that it should self-purge under normal usage but that if air bubbles persist in the pipe disconnect the lever on the left of your pic that connects the throttle lever to the oil pump, rotate the arm on the pump fully clockwise & run the engine at 1000 to 1500 rpm to purge the air. If necessary gently pinch the fuel inlet pipe before the brass 3-way connector to create a slight vacuum. I fitted the bottom of the pipe first & filled it with oil before reconnecting the top.
Yes, the faster the engine runs the more oil the pump delivers.
So far, 3 weeks of use showed no problems so fingers crossed mine's OK.
HTH
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Old 05 September 2013, 18:45   #8
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Hi thanks for all your input guys..

Paintman, i only got down to the boat this wkend so i replaced the broken pipe and started her up.. After 3/4 seconds she started to smoke like it should, i dont have access to water at the boat park so i stopped and started about 4 times without trouble but will need to hit the water for a test.. Its not what I would normally do but I'm sure it will do no harm, I'd just replaced the impellor so it was coverd in lube ive looked all over the internet about oil starvation etc and some people say these motors will run for some time withiut oil so like yours i think it will be ok.

What boat do you have your motor on? Thanks
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Old 05 September 2013, 18:50   #9
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17' Dory Sportsman.
Lots of advice on the net suggesting doing away with the oil injection & just using premix. Not a problem with removable tanks but would be interesting with inbuilt.

ETA Be an idea to replace the hose from the tank as well. Although mine looked OK it was as shot as the little one. If you do, remove/slacken the silver cross headed screw you can see at the top of the pump in your pic then loosen the cap on the header tank which will purge air from the new hose & the pump. Stick with clear hose as you have a visual of oil presence.
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