Mercruiser manual

JackP26

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Jun 12, 2017
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I'm having engine problems and I want to repair it myself but I can't seem to find a manual online that fits what I have and what I want to do.
Anyways I just received a 1972 fiberform, mercruiser engine 120 4cylinder. The serial by the flywheel is 3129562, stern drive serial is 2970146
If you could help me out I'd be forever grateful, I've been banging my head for the last month trying to get the boat fixed so I could get it on the water to enjoy fishing and family festivities.
Thanks in advanced.
JackP26
 

JackP26

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Jun 12, 2017
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I'm having two issues. One being that I don't have a spark from the coil, which I just bought a new one and misplaced the receipt, just my luck. Two, I'm not getting any fuel. I completely disassembled the carb and cleaned every component and reassembled it. I've checked the fuel lines for clogs. Even the fuel tank float. There's a primer bulb with a filter inside that's on the line leading from the tank to the pump. I've disassembled the pump and cleaned it. All the components were in good shape. Even got it a new fuel filter. I've replaced the rotor, condenser and the breaker inside the distributor. Spark plugs and wires were replaced last season. I've given the engine an oil change and replaced the oil filter. Father-in-law says he had the boat running mid winter and started right up with no problems and says that I've hooked something up wrong to the battery. When I have the battery on all my dials, gauges, bilge pump and newly equipped fish finder work. Im thinking it could be the coil or I have a shorted wire.
 

GA_Boater

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When pumping the primer bulb does it get hard and gas is getting into the carb? Does the drive raise and lower with the trim switch?

Manual #1 in the link to Boatinfo has troubleshooting procedures for both fuel and ignition. I'm not much of a Mercruiser guy, but we have plenty of members who are.
 

JackP26

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Jun 12, 2017
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Actually the trim gets stuck about half way. So it doesn't lower all the way. I have bought grease and gear oil and wanted to refer to the manual to make sure i don't miss anything that needs lube. As far as the primer bulb goes the simple answer is no. I can squeeze the primer and it will get harder to squeeze but it remains bone dry. Could it be issues with the vacuum at all or water pump? I've been told there's no circuit breaker or fuse. I've kinda hit a dead end and don't know where to begin
 

achris

More fish than mountain goat
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May 19, 2004
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27,468
Fuel problem.

Pull the line off the outlet side of the primer. Do you get fuel? If no, then suspect an air leak in the lines, or a broken off tank pick up...

No Spark.

Turn the key ON. Check for voltage at the + side of the coil. (Meter or test light). If you have voltage, then turn the engine by hand to get the points open. Take a wire and connect one end to the - side of the coil. Touch the other end to the engine block and check for a spark from the top of the coil. If you have spark, the problem is in the distributor cap.

Chris..........
 

Bt Doctur

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Aug 29, 2004
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That would be manual 1 .If it has old points in it there oxidized and will not make contact, use a nail file for testing, then replace them
 

Alumarine

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Feb 22, 2005
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Thanks, Marc.

When I looked, the manual wouldn't open, so I didn't want to link to dead air. Boatinfo seems to have it's ups and down.

You're welcome. It was slow this morning. It took about 5 minutes to open.
 

Bt Doctur

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jack, testing out a link from the cloud , just stand-by and check your messages
 
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JackP26

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Jun 12, 2017
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Hey sorry I haven't been on. Got busy with the family. The fuel lines are clear and the tank float is good. I blew into the line on the primer side and had fuel coming out my tank vent. Fuel gauge works.
The no spark issue: I took off the coil lead that goes to the distributor and didn't get a spark. Im going to the store tomorrow for a meter. Although I have a circuit tester. Would that work for testing the coils positive and negative voltage? Or do you think my points in my distributor are off?
 

JackP26

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Jun 12, 2017
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I've replaced my points, condenser and rotor. So my timing might be off but I'm not sure. I turned the cam to the flat side to make sure my points would close then I just tightened it there. Thought that's how it was supposed to be.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Turn the engine so the cam has the points fully OPEN. Adjust the points gap, at that point, to the specified gap (in your case 22 thou, 0.56mm) and tighten the screw... Once the engine is running, set the timing.

Chris.........
 
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JackP26

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Jun 12, 2017
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Keep running into little speed bumps. Can I bleed the hydraulic system? My trim isn't going down past halfway. Refilled the hydraulic, drained and refilled the gear oil on the stern drive and greased the three points on the stern drive. I feel stupid that I can't get this going with how many man hours I put into this.
 
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