'78 75 hp Timer Base/Stator help

[TrollPro]

Hello, first off thanks for any help I may get. I've looked into my problem and searched around but I'm not sure if I am performing the tests right.

Let me back up a little, I have no spark on my top cylinder, after replacing the coil, powerpack, and rectifier, still no spark. That left the stator and/or timer base. I'm trying to bench test these with a fluke 179. I have a basic understanding of how this meter works, and have seen values all over the map online for the stator and timer base.

FWIW My garage mechanic said that its highly unlikely that a bad stator would only effect one coil so I haven't tested the stator as of yet.

What I found on the timer base is that any of the sensor wires when tested to the black ground all come back around 8 ohms. Would this be considered weak and needing replacement? I also messed around a bit and when I put the base back inside the flywheel and spin it the reading will spike to around 15-20 ohms, again not sure if this is considered within spec, or just inconsequential. I also see values for DVA listed, is my meter capable of taking these values? Do the parts need to be hooked back up to the powerpack and the engine cranked to test them?

Just to add a little more spice to this post, upon removing the flywheel I inspected the taper and found it to be pitted from where the sheared/smeared key was, along with the keyway on the flywheel being slightly deformed, just enough that it wont accept the new key. I figure I can touch the keyway up some to allow the key to seat tightly without mucking up the keyway any more. I've read conflicting reports on using valve lapping compound on the flywheel and crankshaft, but I doubt I'll be able to completely remove the pitting with the lapping compound alone. Other sources online said to not lap them, and to instead use loctite (either red or blue) on the taper and torque to spec. Which is the best idea, outside of buying a used flywheel (last resort for an engine this old).

Before anyone asks, I have corrected the problem which caused the flywheel key to shear in the first place. Which was a blown exhaust manifold gasket caused by a slightly warped manifold plate, caused by the engine overheating, caused by a blown impeller, all fixed now (do I get my outboard tech certification yet?! lol), just need to correct this ignition issue and get it back on the water!

Thanks again for any help!

 

[F_R]

Holy crap! Do NOT locktite the tapers, if you want to ever get the flywheel off again. Lapping is ok. Don't worry about the pits, get the high spots off. Tapers must be clean and dry and nut tightened to 100 ft pounds. Somebody didn't do that, which is why it sheared the first time.

It is highly unlikey that all three sensors are bad (especially with all 3 testing the same). You are getting goofy ohms readings when you turn the flywheel because you should never do a resistance (ohms) test on a circuit that is carrying a voltage. The sensors generate a voltage when the magnets pass by. But what you did do does prove they are generating a voltage, which is what they do for a living.

A DVA meter is a Peak-Reading Voltmeter. It reads the highest voltage it sees and holds it till you can read it. I don't know if your Fluke does peak-reading or not. Probably not.

I don't know what the problem with your motor is. But usually a no-spark on only one cylinder is a bad power pack. But you replaced yours, so....?

 

[racerone]

You just have to use the lapping compound !!--------That is even specified in the factory manual too for some models!!---------That key is NOT a hardware store item and you must use the factory key.----------Note-----The close fitting tapers lock when properly torqued.------This is what drives the flywheel.-----The key merely locates it for proper timing.----------No need to use loctite at all !!

 

[TrollPro]

Well after I replaced the pack is when I realized the timing was off, and when I mean off, I mean 180 degrees off.

The timer base sensors were pretty well worn and cruddy before I cleaned them up and tested it, perhaps cleaning it solved the spark issue and I just need to lap it back together and see if it fires. Or possibly when the key sheared a chunk got stuck on sensor or something. I did inspect all the wires for signs of melting from the overheat and found none, also checked for shorts on every wire and found none.

The trouble shooting guide from CDI says that OEM spec on the timer base wires to ground should be between 10-20 ohms so I'm worried that its low. I think you have to take the PVA reading with everything hooked up and cranking it correct? Would hate to put it all back together only to still have the no fire issue on the top cylinder.

Ok I will not go the locktite route, I honestly didnt want to do that either. Getting the flywheel key out of the crank was a huge PITA but I did it without using any heat, utilizing punches, flat head screw drivers turned chisels, and drilling the key out a bunch of times. The straw that broke the camels back was the CRC Freeze Off. I cleaned up the crank shaft and fortunately that key way is pristine. The flywheel keyway has some deformation that is almost imperceivable but is enough that the OEM key is not sliding down into position. I'm going to try and lightly file the sides of the keyway then hit it with 600 grit sandpaper, followed by crocus cloth.

 

[F_R]

My factory service manual (1974) says 8.5 ohms, plus or minus 1.0 ohm.

 

[TrollPro]

That makes me feel a lot better as they are reading right at 8.5.

Does anyone have a handy link for how to set the gaps on these sensors? I think you need a special tool but can rig a field expedient version I thought. I could be wrong.

Does my procedure for fixing the keyway sound safe?

 

[racerone]

The correct procedure is to use lapping compound.----These tapers must be matched .------The correct flywheel key is very important too.-------A simple concept that is often not understood.

 

[TrollPro]

After lapping the flywheel (that took way longer than I thought it would, but I got it done right), interestingly you could tell when it was starting to get matched as the flywheel would stick and not want to pull off. I lapped it a total of 4 times, using straight paste, then progressively more water on each rotation until finally a pencil mark on the crank dissapeared after a 90* turn.

Also used that rope trick that I read in the SN Striper 171 CC resto thread to stop the flywheel from turning so I could torque that nut down. My book specified 105, and I looked away to check the dial and didn't see if it moved after 100ft lbs, but I kept at it and it wouldn't budge so I'm assuming its plenty tight.

After that a couple o squirts of starting fluid and she roared back to life. I was hootin and hollerin so loud the whole neighborhood could hear lol. Its been a battle with my first "big" outboard and I'm glad I came out on top this time.

I assume that I dont need to mess with testing the stator or timer base as it was running very nicely (although the idle is WAY to high), gonna link and sync the carbs up again and adjust the idle and the timing and I should be back in action just in time for the walleye run!

Want to thank you guys again as I probably spent 30 legitimate hours scouring these forums and found all sorts of useful information.

I'm sure you'll be hearing from me again as I need to replace the bearings in the prop housing (discovered ALOT of heavy mono had wound on my propshaft and fused to the bearing and now its leaking gear oil/water from the propeller). Seems fairly simple and straight forward to change them out in my manual, but then again, nothing with this motor has been simple or straight forward for me.

Thanks again!

 

[TrollPro]

Then again, maybe its just old sludge from the copious amounts of wd40, pb blaster, and crc freeze off im sure made their way through the leg and into the exhaust? There was a fair amount of carbon build up in it as well when I changed the exhaust manifold gaskets.

From my understanding the biggest worries with water intrusion into the lower unit are corrosion and water freezing inside? If so I could get away with testing the boat on the water under load?

Lastly, I saw a method for statically setting the timing advance on the marine doctor website, should I do this or not do this? I wont be able to get the boat into the shop and in the test tank for at least a month (he is that backed up) to be able to set it the proper way so was hoping this would get me in the ballpark.

Thanks again.

 

[racerone]

Water inside a gearcase is a no,no---You would be shocked at what the parts and pieces cost.---Best is to pressure test and install a seal kit if need be.

 

[TrollPro]

I agree, and its definitely in my plans to tune up the lower unit, but getting the power head to run ate up my fixaboat fund so I'm unable to redo the lower unit seals right now. I do know I can get a used/remanufactured lower unit for 5-8 hundred dollars. So if I can get one fishing season out of the current lower unit it without it blowing up I'd be happy to replace it next winter.

The way my mind is processing this is I can sit on the boat, put it back in storage, and wait until I have the money and time to redo all the seals and gaskets on the lower unit, its probably the proper thing to do. That said, most people dont even check their gear oil but once a season, and I'm sure not everyones seals leak on the very last trip of the year so the lower unit would have ran for some length of time with the water intrusion before it was detected.

My plan was to get the boat on the water, test it under a load. If it runs good under a load then back on the trailer to the drive way it would go to sit for a day, allowing the water an oil to separate. Drain the lower unit, while capturing the first amount in a clear plastic bottle to see how much water made it into the gear case from that one trip. Depending on how much water I get I would change the gear oil more frequently, ie 250ml of water, I'd change the gear oil every 2 weeks, 150-250ml every 4 weeks, 50-150 every 6 weeks.

I've also read an old post on here (maybe the hull truth or something similar) that others have done this for short periods of time with success.

I know its not good, but I'm running out of options