please help me repair a 1979 70 hp Merc

[Bill kubiak]

I have serial #4048399, I got this as part of a deal, the lower unit is off and the engine I was told will not start. I have many questions and will post them one or two at a time. this is the motor without a distributer<br /><br />There are two shock absorbers one on each side of the motor, there is no plumbing attached to them, what are they for and how shall I remove them? <br /><br />To crank it over using the starter motor how do I hook up a battery. There are many wires loose on the motor the first thing I want to check if there is spark on each plug<br /><br />I put some mystery oil in the plug holes and now I can just barely turn it by hand, so it has good compression on all three cylinders

 

[Bill kubiak]

Re: please help me repair a 1979 70 hp Merc

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[SeaHorse]

Re: please help me repair a 1979 70 hp Merc

I have the same motor. <br /><br />The shocks keep the motor from slamming back down after you run over a log. Why are you trying to remove them?<br /><br />To crank the motor it should be in the normal upright position and connected to the control box. Do you have one? For any motor testing you should put a new water pump impeller in the lower unit then put the lower unit back on then hook up "earmuffs" to force water into the lower unit water inlets while you test.<br />You should try to get the factory service manual for the motor. It is Mercury part number 90-86135--5.

 

[Bill kubiak]

Re: please help me repair a 1979 70 hp Merc

The motor is off the boat, it appears that the wires were cut at the transon. I do not have a key for the ignition switch.<br /><br />What I want to do it put it on a stand and crank it over to see it it has spark, Are there any precautions I need to do to keep from burning something up like a control unit or power pak or something?<br /><br />There is a tilt switch on the remore control unit, how can I check to see if the motor has a power tilt/trim system?<br /><br />Bill

 

[andrewkafp]

Re: please help me repair a 1979 70 hp Merc

You need a manual which will have a wiring diagram show all the colours and where they go. I think ALCAN or some of the other members may have a electronic diagram that they may send to you, but there is no substitute for the manual. BTW . Don't try to guess anything, as rectifiers and CDI's are very expensive to replace.

 

[Bill kubiak]

Re: please help me repair a 1979 70 hp Merc

I have an Intertec generic manual I got from the library. 8 pages on this motor, It does not have real clear photos or diagrams.<br />Does this motor have a tilt trim system? The book says there are two, a non integral and an integral, but does not go into real detail about what they look like. Are those shock absorbers actually part of a trim system or was a trim system an option???

 

[agrazela]

Re: please help me repair a 1979 70 hp Merc

Bill,<br /><br />I too have the same motor, though it is a 1978.<br /><br />I do not believe these motors were available with power t/t. Is the control box a Mercury "MerControl" or an aftermarket?<br />If you have the regular t/t pistons as I suspect, I would suggest you not screw around with these unless they are totally siezed.<br /><br />As for your question; yes, the ignition coils and the switchbox MUST BE GROUNDED or you will burn them out (so says my manual!)<br /><br />I definitely suggest a manual, too. I bought the SELOC manual for my motor, and it seems to serve me OK. It has a good checklist for what to look over (both mechanically and electrically) on this motor, and a complete wiring diagram in the back (the wiring on this motor is actually quite simple).<br /><br />If it helps any, the compression readings on my 3 cylinders are 150-145-155 psi.

 

[andrewkafp]

Re: please help me repair a 1979 70 hp Merc

My 1980 50hp does NOT have power trim and the transom mounting has 2 shockers, a lever, operated from the top of the bracket and 2 reverse /neutral locks.<br />If you have power trim, it will be easy to spot, as there will be hydraulic lines coming out of it somewhere, and a hyrdraulic pump somewhere on board. Does your '79 have a distributor or coils ? I would think it would be coils.<br />This is an 83 with power TT<br /> http://www.myfishingpictures.com/watermark.php?file=500/14131983-50.jpg

 

[Bill kubiak]

Re: please help me repair a 1979 70 hp Merc

It does not have power trim/Tilt, no lines, no pump and it has merc controls in the cockpit.<br /><br />If I make sure the coils and elect control box are grounded can I hook a battery up to the starter solonoid and the ground post on the engine block and use a remote auto starter switch to spin the motor to check compression and see if I have spark?????<br /><br />Is there an adjustment somewhere to loosen the pivot points for steering??<br /><br />I am willing to even trade this motor for a 25 OR 30 HP merc if anyone in the S.Fla./Miami area is interested. I think it is way too much power for the 12 ft boat it was on.

 

[Bill kubiak]

Re: please help me repair a 1979 70 hp Merc

Ok here is what I have done so far, cleaned all the electrical ground connections and connected a battery to the engine<br /><br />I jump wired the choke solonoid and it works and the enrichment valves move<br /><br />I spun the engine with the starter using a remote start switch by jumping the solonoid and I have from top to bottom 115 psi 110 psi and 95 psi<br /><br />Will someone please tell me how can I turn the ignition on with engine on a stand, so I can see if am getting spark??