Tohatsu M40C timing issue.

[25432]

I've never seen this motor run well since i got it, but after wearing out the search button and buying a service manual I'm now getting 28 mph @ 5600 RPM on a 14' High Tide with 2 people (400 # total in a heavy fiberglass boat which may or may not have wet floatation). Anyway, when setting the timing earlier today I either don't have the range of motion to achieve 25? BTDC and 2? ATDC or I'm missing something. The slow stop is a fixed piece molded into the block so it's not adjustable. I set it for 25? BTDC at full throttle which has me between 0? and 2? BTDC at zero throttle.

I took it to the river this afternoon and made a few runs and wound up raising the motor to the next to last hole on the high side and having to play with the timing a tad to lose an intermittent sputter.

On the water I changed it to 2? ATDC at closed throttle which gives me around 21?-22? BTDC WOT and got the sputter so rather than using the marks as a guide I used the motor's performance a guide and found a happy place for it as I went back towards 25? BTDC incrementally. Any explanation for why I can't achieve both settings?

Also, as has been alluded to before in several threads, these motors like to be a little higher mounted than most....I wish I would've built my transom up another inch maybe even an inch and a half....

 

[25432]

Re: Tohatsu M40C timing issue.

FWIW, I have a CMC T-n-T unit on this setup as well.

 

[pvanv]

Re: Tohatsu M40C timing issue.

Check for any wear/play on any of the rod snaps or connectors and associated bits. You should be able to achieve a range of at least 27-30 degrees total swing.

 

[Sea Rider]

Re: Tohatsu M40C timing issue.

You can leave ATDC at 0? will have less end grip play at turtle side. Probably will need to adjust idle screw down a bit to lower rpms that tends to go tad high when adjusting to 0?. With warmed angine, adjust to 850 rpm when in gear on water. Check Upper bolt Joint B & Cap C ball joint, both middle Rod Snap, and lower Cable pin & Rod joint for wear end excesive play, if found so, replace all 8 or just very critical parts 1 & 2 as will produce magneto plate timming lag issues with respect to carb. Grease well before assembling back.

Happy Boating

 

[25432]

Re: Tohatsu M40C timing issue.

Check for any wear/play on any of the rod snaps or connectors and associated bits. You should be able to achieve a range of at least 27-30 degrees total swing.

The "eye" connector at the magneto end of the linkage wasn't fully engaged, but the rest seem to not have enough play to cause any issues. I think it may be lost in wear at the gears in the tiller handle to be honest with ya, but it's running so good now I'm leaving it alone.

You can leave ATDC at 0? will have less end grip play at turtle side. Probably will need to adjust idle screw down a bit to lower rpms that tends to go tad high when adjusting to 0?. With warmed angine, adjust to 850 rpm when in gear on water. Check Upper bolt Joint B & Cap C ball joint, both middle Rod Snap, and lower Cable pin & Rod joint for wear end excesive play, if found so, replace all 8 or just very critical parts 1 & 2 as will produce magneto plate timming lag issues with respect to carb. Grease well before assembling back.

Happy Boating

I wound up at 0? ATDC and indeed had to bump the idle down.

Thanks for all y'all do on here, big thumbs up!