1988 mercury 35 - dies on water and can't restart ** eats flywheel magnets

[Baitcooler]

Hi again. New trouble, new topic. This one will be slightly longer so hang in, please.

1988 35hp merc. I rebuilt the fuel pump (bulb wouldn't stay firm). I fixed a mechanical problem with the reverse-lock pushrod. I didn't mention this before, but I'm on my second flywheel. I lost a magnet on the first one which got me into a no-start, no-spark problem I was able to fix with a new flywheel. The flywheel came off of a parts motor I was lucky enough to find locally.

I did my second water test over the weekend.

It was more difficult to start on the ramp than it was in my side-yard trash can. I also had to keep the revs up when in forward or else it would stall immediately. That was new.

I launched and started to run up a creek I sometimes fish. My fishfinders were complaining about low voltage. I stopped to make a few casts. I watched the voltage and with the motor stopped, it was the same. I expected it to go lower with the outboard off (more on this later).

After thinking about how it was hard to start, and my battery was not charging I decided to crank it back up and head back towards the launch ramp. It started about the same as on the launch ramp. At speed it started to lose power intermittently. Maybe one of the cylinders was cutting out? I don't have an ear for these problems, yet.

I kept the hammer down and my fingers crossed. In a bend I ran up on another fisherman anchored putting out live-bait rods. I backed off the throttle. The motor died. I tried to restart it. No luck. The man was very nice and towed me back to the launch ramp!

Monday after work I took the cowling off. I told myself I was only going to look at a few things and not get too dirty before dinner. I tested the rectifier. The rectifier diodes that connect to the positive side were open. That explains the low battery warnings. I'm considering that one sorted.

After the rectifier I pulled the plugs. They looked good. I kept snooping. When examining the motor I noticed a piece of flywheel magnet in the lower cowling. I fished it out. With plugs out, kill-switch yanked, and key out I turned the flywheel by hand and looked at the underside for magnet damage. Chunks were missing.

I popped the flywheel off. There was definitely new magnet damage. The no-start I'm experiencing now eerily resembles the no-start I had when the magnets were damaged on the first flywheel.

What gives? Was this the source of my power loss on the water? How are these magnets so fragile and is there a way to replace them? The flywheels don't seem to exist for my 35, at least where I know to look (ebay). When I ran into this with the first bad flywheel, I tried to replace it with a flywheel from a slightly older 40 and it rubbed on the ignition stator. That's when I got lucky and found my parts motor locally. The magnets on the parts one were also damaged, but it started and ran well enough when I swapped it over.

What else can I eliminate? I should have tried with starter fluid before removing the flywheel, but you know..... hindsight, man..... It cranked hard and smelled like gas on the water. Even with the neutral fast-idle lever pulled all the way up, choke or no choke it didn't fire. I didn't think it was a fuel problem then.

I'll post some pictures later of the flywheels. If you have any info on compatible flywheels for a late 80's 35, or know anything about replacing the magnets I would greatly appreciate it. Thanks!

 

[SteveVT]

Hi I have an '89 Mariner 25hp whose magnets came loose in storage. They were intact, however, and so after a LOT of research about positioning, and very careful metal prep, I glued them back in place with JB Weld epoxy. The engine runs fine now.

I'm guessing that the OEM glue used (in this late 80's era at least) won't necessarily last 30 years, so I'm not personally surprised that you had two sets fail in a row.

Yes, magnets are quite brittle/ fragile, in themselves. They are however glued to the cast iron of the flywheel, and that supports them. If anything hits them (like an out of position coil) they can break apart. So you first have to determine if there is any possible interference in your stator and trigger assemblies. But my guess is just that the original glue line gave out. BTW it isn't necessarily the glue itself -- cast iron rust can propagate under the glue.

I don't know if this is really much of a help, since your magnets broke apart, while mine stayed intact, and could be replaced.

I will say that I had a similar problem with an equally old stored Minn-Kota trolling motor, and in that case the magnets not only came loose inside the motor casing but one also broke in half. Figuring I had nothing left to lose there, I glued that one back together, and both back inside the casing. I've used that motor three years since the repair with no problems.

I do want to add a caution, however about gluing magnets to an outboard flywheel. If they ever come free or break up at high speed, the out of balance forces could conceivably bend a crankshaft, or even shatter a flywheel with very dangerous consequences.

I felt I knew what I was doing, and it was my own personal choice. I didn't just slap on magnets willy-nilly with any old adhesive. I went to bare metal on the flywheel and clean magnet surfaces, added JB Weld (which I personally believe is an epoxy adhesive best matched to the application) then AFTER that, sanded slightly with coarse paper while the wet glue was in place to remove any additional momentary oxidation and ensure a chemical bond. The trolling motor application was much less critical, since the magnets are stationary.

So be aware that this is NOT a recommendation to anyone to glue magnets on an outboard flywheel. Just an explanation of an experimental personal choice I made, where I felt I could achieve as good a bond as the original, using intact magnets, and obviously better than the original glue line at 30 years of age, which failed. Your mileage may vary.

 

[Baitcooler]

Thanks for the reply. I was thinking about using gray marine tex. Here are some pictures.

Do you think the one I had installed is damaged enough to provide sufficiently weak spark? Weak enough that it won't start?

 

[Baitcooler]

OK. Scored another flywheel. When this doesn't fix it be prepared for all of my other questions haha. AKA --> If it's from the 80's and has a carburetor...

Hope everyone is having a great weekend. I'm already stuck sorting out work problems remotely.

 

[Baitcooler]

Hi all. I wanted to follow up and report back on my progress.

The gas smell on the water when attempting a restart was a bad connection from the fuel filter. I squeezed the bulb and watched closely with the cowling off in the side yard and found it. The hose was 3/8" ID and the filter fitting is a 5/16". Someone had reworked that area before. It probably sealed-up at the time but NOT ANYMORE!

I replaced all the outboard fuel line from the inlet to the carb. I replaced the fuel filter. I had previously rebuilt the fuel pump and replaced hose and bulb between tank and outboard. While I had it apart I was suspicious of the carburetor as well. I ultrasonic-ed it and threw a rebuild kit at it. For the most part it looked OK. The needle valve was the worst.

So, after rebuilding the fuel system from gas tank to power head, and reassembling with new flywheel, the motor started and idled effortlessly. Then it got dark. I'll tune it the next day it doesn't rain LOL.

I do have one question about the carburetor... The hose that goes across the top for the economizer was starting to rot and the plastic 90 degree fitting near the welch plug had a crack in it. I replaced the hose. I looked at the parts catalog and the 90-degree plastic fitting is not called-out as a separate part. What is this called and is it replaceable? If it fails should I plug the hole or leave it open? There are a few topics where guys on here talk about disabling the economizer and I want to make sure I understand the trade-offs.