115hp 6cyl questions

[ranger79]

ok i have a '79 inline 6 cylinder 115hp merc "tower of power". it got hard to start and then would not start at all. simple tests showed no spark except on one cylinder and it was an off color spark. took to merc dealer and after a week and a half found out i need new switch boxes and a stator, and they were not going to work on it which was fine by me since the estimate was way more than i want to put in the boat. my question is how much work is actually involved in replacing these parts? if i purchase and replace the switch boxes myself and have a local marine mechanic do the stator i think i will be fine. anything I'm missing?

 

[achris]

Re: 115hp 6cyl questions

Nope... CDI do a reasonable switchbox/coil replacement... And you can get the stator there too. Just one thing.. the stator on these engines only charges the battery. Unless you have a battery charging problem the stator shouldn't need to be touched. And if you do have a battery charging problem, then I would be checking the rectifier first....

And if you have a battery charging problem, then fix that, charge the battery and retest for spark.... Low battery will kill the spark on these engines.

Chris........

 

[ranger79]

Re: 115hp 6cyl questions

thanks!!! The wires that concern me the most are coming from under the flywheel going to the switch boxes. two of them have insulation that is cracking, but the rest are pliable. one of crusty ones was the only one that had spark! i am not concerned about the battery staying charged as i always charge before heading out on the water, and have a seperate battery for the trolling motor and electronics on board. i am planning on ordering and replacing the switchboxes (cdi) and going from there.

 

[ranger79]

Re: 115hp 6cyl questions

one other thing, while the motor was running the depth finder would show and icrease in voltage. that may have changed since it stopped running, but we will see. i have heard/read that bad switch boxes can ruin stators. again thanks for any advice. just another boater frustrated by the problems that come with the territory!

 

[achris]

Re: 115hp 6cyl questions

ok... is this a non-distributor engine or an engine with a distributor?

I was referring to distributor.... If you're talking about switchboxes, then it's non-distributor.... in which case I was talking out of my hat (you thought I was going to say something else, didn't you... )

The switchboxes and stator are still available from CDI, but if you have flacky wires, then it does need replacing... I would replace the stator and see if the sparks return before getting the switchboxes. Also check the trigger wiring... That may be flacky too.... also available from CDI.

Chris.......

 

[achris]

Re: 115hp 6cyl questions

one other thing, while the motor was running the depth finder would show and icrease in voltage. that may have changed since it stopped running, but we will see. i have heard/read that bad switch boxes can ruin stators. again thanks for any advice. just another boater frustrated by the problems that come with the territory!

These engines have an unregulated charging system (which is why it's ESSENTIAL to use a MARINE battery) and for the voltage to continue to rise is normal. I have seen it as high as 17 volts....

Chris........

 

[ranger79]

Re: 115hp 6cyl questions

non distributor. two switchboxes. the wires that are flakey are from the trigger i would guess. i dont have the equipment to pull the flywheel to be sure, but they are the 6 that go to the switchboxes. from the looks of it (rubber caps off terminals) the dealer checked out the swithcboxes and found them bad.

 

[asm_]

Re: 115hp 6cyl questions

These engines have an unregulated charging system (which is why it's ESSENTIAL to use a MARINE battery) and for the voltage to continue to rise is normal. I have seen it as high as 17 volts....

Chris........

Just want to ponit out, Marine battery or not, extended period of apply voltage over 15v kills any flood Pb battery just the same. That's why it's always better to add an after market regulator. Or, check battery fluid level monthly to make sure lead plate is still submerged.

B

 

[arsenalpsu]

Re: 115hp 6cyl questions

definitely replace the stator before you purchase new switch boxes. You can't test the boxes if you're stator is bad. You don't need a lot of tools to pull your fly wheel, just go to e-bay and get a puller for +/- 30 bucks and make sure you have the correct size socket and that's it. I put a screw driver between the starter and the gears to hold the wheel, just don't do any sudden jerks or you could break teeth.

 

[Chris1956]

Re: 115hp 6cyl questions

You guys give those dinky (9Amp) Merc charging systems a lot of (undeserved) credit. They will never fry a 24 series lead/acid battery. A marine battery is a bit more heavy duty (and they have wing nuts and a handle) than an automotive one, but they are esentially the same.

If your electronics are sensitive to high voltage, you may have some issues, but this is fairly rare.

 

[ranger79]

Re: 115hp 6cyl questions

thanks for the help everybody! just an update......i kinda jumped the gun and ordered the switchboxes and replaced them before finding out about the suggestions to replace the stator first. apparently I got lucky as now i have a good blue spark on all 6 cylinders and the engine fires up and idles smooth. i am going to put a voa meter to it to check voltage to the battery while running to be safe. i also had a bit of a typo on the increase (increasing) voltage on the depth finder. i would see as high as 13+ volts but no higher than 14. i still have work to do but at least it appears i am gaining! thanks again to everybody!