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Tohatsu m70c need help

J

Jake90

New member
Well I have a tohatsu m70c which I bought recently and am having dramas. Compression on each cylinder is 120, 120, 115. Is starts up perfectly, and cruises around on low revs no worries, I can get on the plane and sit on maybe 1/2 throttle no worries, just when I really pick the revs up and come close to "wot" it will only last for about 2 minutes before it bogs down real slow and runs very rough for about 20 seconds, then if I leave it full throttle it will pick back up by itself. Or once it bogs down, if I bring it back to neutral for a second and hit full throttle right away it comes good again, only for another minute or two until it bogs down again. Only when I'm going over 4000rpm or so. So once it bogs down and runs real bad for that 20 seconds, I have pulled each spark plug one at a time and was hoping that when pulling one Of the plugs, I would not see any change, then hopefully it was an ignition problem (ignition coil maybe) although I noticed a change on all 3 plugs so all cylinders seem to still be going while this is happening. I have squeezed the primer bulb once it bogged down to rule out the fuel pump and it made no difference, I also pushed the choke while it was bogged and it didn't make it better, just nearly cut out like they do. I have cleaned out both internal and external fuel filters, oil filter, sprayed carb cleaner in carbies, changed primer bulb and it's still doing this. I have hit a brick wall and don't know where to look no more. I do believe it could be a fuel problem because of how consistent the problem is. Any help would be much appreciated. Thanks, jake.
 
Did you verify link and sync? Proper carb cleaning cannot be done by spraying, so you may need to clean the carbs correctly as well.
 
What is a timerbase? Link and sync refers to adjusting the synchronization and limit stops of all the linkages so that ignition timing matches carb throttle position, and all carbs are in sync.
 
I have been told to make sure the link under the flywheel moves freely as I increase throttle and advances all the way to the bolt that stops it. The fella telling me was refering to that link as the timer base. But nah, I have not verified link and sync, I'll have to do that next, does that process vary between different outboards? Cheers for the help so far :)
 
In order to verify link and sync, you need the Factory service manual. It is different among brands and models. Have you also completely disassembled, soaked, and blown out all the carbs? They likely need that.
 
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