Mid 80s Johnson 70hp Help

[andrew j cox]

Hey guys, I have a mid 80s Johnson 70 Im trying bring back to life, it was on a boat I saved didn’t plan on keeping it so did nothing with it, the motor I was going to use is no good, so now I’m looking at the Johnson that’s on it, I don’t know these 3 cyl loops , I put a battery on it, fuel to it, she turn over but there’s no life, I need to where to start trouble shooting it, Spark would be number one
The Tilt / trim has two wires, how do I test it , using the switch on the gear shift there’s nothing no life, im thinking there’s a wiring gremlin maybe.

 

[jakedaawg]

1st would be a compression test. Looks like you need to address the battery cables to accomplish that though.

 

[Jehu1]

Sir,

To start looking at your Trim Issue if you look at the link below (well its almost a link forum does allow those so copy and paste it in your browser with www in front of it) you will see a diagram for a 1985 Johnson 70 trim unit,

boats.net/catalog/johnson/outboard-by-year/1985/j70elcos/power-trim-tilt-hydraulic-assembly

These units vary in complexity internally but all the hydraulics are activated by the motor spinning either clockwise or counter clockwise which pressurizes the hydraulic fluid in the unit lifting the Motor up or letting it down so to figure out if you trim unit itself is working so find item # 78 (motor connector plug) and disconnect it, once you have disconnected the plug get two wires and hook them to a good battery's positive and negative posts being EXTREMELY CAREFUL not to short them out. Then in the safest way you can connect the wires FROM THE BATTERY to the two connections inside the plug, it doesn't matter which one you put where positive or negative because the trim motor will be activated either way, one way is up and reversing the leads will cause the motor to spin the other direction letting the trim unit go down or vise versa. Testing it this way you are removing the entire electrical wiring in the boat from the trim unit so you know which direction to start troubleshooting your issue. hope this helps.

 

[Jehu1]

rats that trick didn't work for the link either.. go to boats DOT net to look up a schematic of your motors trim unit

as to you motor issue the compression test is absolutely the first thing you need to go as you were advised previously

you can do this without a battery if you really need to even though a 70 is a little big to crank by hand, however you can remove all three spark plugs, then place your compression gauge in one of the spark plug sockets on the cylinder head one at a time then use an electric/battery powered drill on its low speed setting (max torque) with an appropriate socket that fits the on the fly wheel nut and turn the motor over that way to get your compression numbers. those numbers will tell you if there is any hope for the motor or not. Good Luck

 

[Faztbullet]

That may be a 80's midsection but the powerhead is a1974 49ci Stinger.