Tohatsu m50c starter issues.

Marley88

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Mar 4, 2014
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Alright, I've been browsing these forums for a quite a while and, thanks to the experiences and advice of the members here, have successfully diagnosed and fixed a few of my prior outboard problems, but am finally in a spot where I believe my first post is required!
The motor is a older Tohatsu m50c 2 stroke on a 16 ft StarCraft, both of which were just purchased. Considering the price, I was somewhat expecting some work to be needed, even though it test-ran decent when purchasing. I have, in the past few weeks, replaced the water pump impeller and housing, fixed the shift linkage to the lower unit, reversed the steering, fixed the tilt and trim (temporarily), new plugs, and completely took apart and cleaned out both carbs.

This last time I took it out on the water (prior to carb cleaning) was the first time I had really opened up the throttle after the initial repairs I did. It idled fairly rough, cruised at low speeds for about 10 minutes, and when I gave it some gas it got up on plane GREAT and pushed the boat even faster than expected. Ran full speed for about 3-4 minutes flawlessly then started to bog down really bad, eventually dying. Seemed like it was flooded and could see gas running out if I pumped the ball. Pulled it back to the ramp (2 miles on foot via sandbar lol), where it then started (slowly) once we were back, of course. got home and hooked it up to the muffs to flush it. It started, allowing me to flush it, but the starter turned over rather slowly. Now my diagnosis for both problems: considering the performance, the fuel leaking out the carb when ball squeezed, and the fact that boat sat for about 6 months, I figured the carb was super dirty and gunked up causing the bogging/flooding. As for the two weak starts, I was just assuming I had ran down the battery while trying to crank it so long while on the water in conjunction with the lights/electronics.

I removed and broke down both carbs, saw that everything was extremely dirty and gunked up as expected, used a full 2 cans of carb cleaner on every part and hole, dried with compressed air, then reassembled everything.
Tried to start it with the muffs on to no avail. starter turned flywheel very slowly (1 turn every second or two) but not enough to actually get it going. Still thinking the battery is just dead, I hooked it up to the charger for a few hours, came back and got same thing when trying to crank it. Went through and checked the wiring and connection points pretty thoroughly. cleaned and cinched down a couple spots a bit but everything seemed to be pretty clean and tight, with no visible corrosion or hot spots. Same slow turn. Unhooked the battery and, after disconnecting the wires from the starter, hooked up the battery directly to the starter post with jumper cables. Still turned slowly. Took the battery from my truck, which I know is good, and again jumped it directly to the starter. Once again, it turned slowly.

Now I believe I have isolated the problem to be the starter motor. I am by no means an expert mechanic, but considering the slow turns when jumped directly from my truck battery, I just don't see how it could possibly be anything else such as the solenoid or wiring.
Would like some more experienced guys to chime in before I just pay for a rebuild/new starter. Any input would be greatly appreciated!
 
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Sea Rider

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Sep 20, 2008
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12,345
Re: Tohatsu m50c starter issues.

Is key starter switch in good electrical condition ? if so, probably internal carbon brushes are too short, worn out making a poor electrical contact against lower armature's rotor slowing motor down. Definitely needs servicing as most OB systems do.

Happy Boating
 
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pvanv

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Apr 20, 2008
Messages
6,500
Re: Tohatsu m50c starter issues.

If you jumpered a good battery directly to the starter motor (I assume you did get a good ground), you have a bad starter motor.

The complete starter motor is available, but isn't cheap:
353760104M STARTER MOTOR $417.36
Perhaps you can disassemble and diagnose the actual failing parts -- could be brushes or mechanicals. Some internal starter motor parts are still available.
 

Marley88

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Mar 4, 2014
Messages
17
Re: Tohatsu m50c starter issues.

thanks for the replies. I'm sure not spending 400 bucks for a new starter and have heard lots of terrible reviews about the cheaper Chinese ones I have seen online. Since I'm not very familiar with the internal components of the starter motor, I was thinking about just taking it into a local starter/alternator shop and getting it rebuilt, as I have heard it can often be done for under 100 bucks. thoughts? If the internal mechanisms isn't too entirely complicated, I may take a look and see if there is any obviously broken components but not sure exactly what I'm looking for
 

pvanv

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6,500
Re: Tohatsu m50c starter issues.

Should be a good alternative. Some internals are available for that starter, so if it gets a proper diagnosis and repair, it should work like new.
 

Marley88

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Mar 4, 2014
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Re: Tohatsu m50c starter issues.

Thanks a lot for the advice. As long as I can get a reasonably cheap quote from the starter/alternator repair shop down the street, I'm probably going to just take it there. Going to briefly look it over before taking it in, in case it's something very apparent, but not too confident in my ability to repair the internal workings.
 

Sea Rider

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Joined
Sep 20, 2008
Messages
12,345
Re: Tohatsu m50c starter issues.

There are few internal components that wears out, usually are carbon brushes which excites the armature's rotor to spin fast inside the body, you could have some sort of rust on rotor not making a good electrical contact, a matter to sligh polish with a medium sand paper. If needed, could take advantage to change lower and upper internal bearings to work as a champ, as when new. Any auto shop that repairs/services starters and alternators can take care of your electric starter at a low cost.

Happy Boating
 

Marley88

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Mar 4, 2014
Messages
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Re: Tohatsu m50c starter issues.

Took the starter in and got it rebuilt at a local shop this morning, for just a tad under 100 bucks. Now it's substantially smoother and faster, cranking the motor easily. This was the first time I had got it started since removing and cleaning the carbs last week. The motor sounded noticeably smoother and vibrated less. Idled for about 20 minutes straight with no problems. I didn't want to go too crazy on the throttle with just the muffs on, but it kept running good the few times I gave it some more gas. Now that I know the starting issue is fixed, I'm really hoping the carb cleaning has fixed the other problem I encountered last time on the water. Will need to get it out on the water this weekend to know for certain. thanks for all the advice!
 

Marley88

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Re: Tohatsu m50c starter issues.

Spent all afternoon out on the bay, with hardly a problem at all! Everything seems to have been fixed. thanks everyone!
 

Sea Rider

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12,345
Re: Tohatsu m50c starter issues.

Spent all afternoon out on the bay, with hardly a problem at all! Everything seems to have been fixed. thanks everyone!

Marley, just for the tech record, which parts were changed to new, carbon brushes, bearings ?

Happy Boating
 

Marley88

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Joined
Mar 4, 2014
Messages
17
Re: Tohatsu m50c starter issues.

For the starter: the guy at the shop said he had to replace the bearings, brushes, armature and perhaps a few other things. pretty much a full rebuild I believe
As for the bogging/flooding at full speed: a thorough cleaning of the carbs seems to have fixed that problem, as It handled very well at full speed, and ran much smoother at all rpm ranges yesterday.
 
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