2003 Tohatsu 25hp M25c3 issues

[hunters_champs]

Hi guys, new to the forums but thought i'd try my luck here with anyone who might be able to help,

Ive got a 2003 Tohatsu m25c3, recently bought the boat, and has always been a reliable engine as a knew the owner.

Just started developing what seems to be a sparking issue, only noticed this recently when i was out boating. I had been fishing for 2 hours, and packed up to go back to where i had parked, 10 minutes along i slowed down for another boat, this is when my issue started, anything over 1/4 throttle the engine seemed to be loosing spark in one cylinder and running as rough as guts.. It doesnt do it all the time, ive only had it pop up twice and do this.

Ive ruled out fuel, tried chocking it to give it more fuel, and it doesnt improve.
Cleaned the plugs, to no avail.
Ive let the engine cool after it has done it, for well over an hour it sat and still done it, next time i went out - no issue!
Had the coil tested, and it come away fine, even heated it up for 3 hours to see if that made a difference.

Couple of people have suggested CDI is shot?


Has anyone else had a similar issue?

Paul

 

[Sea Rider]

Re: 2003 Tohatsu 25hp M25c3 issues

Welcome to the forums,

Could be fuel, mechanical or electrrical issues, will need to troubleshoot them separately, as Paul always advises start buying a service manual and stop making wild guesses. If it seems an intermitent issue, is the hardest to diagnose fast & properly.

Happy Boating

 

[pvanv]

Re: 2003 Tohatsu 25hp M25c3 issues

Yep. Could be quite a few things; Diagnose one system at a time (fuel, electrical, mechanical) and you will find it. Problem with dx for intermittent issues is that they must fail while you are testing for you to definitively dx them. Use the Factory service manual as a guide.

 

[hunters_champs]

Re: 2003 Tohatsu 25hp M25c3 issues

Thanks guys,

Was just fishing to see if anyone may have had the same issue, a local boat mechanic (most experienced in the area) has never had an issue with a tohatsu and seems to think its coil or CDI, we ruled out fuel and mechanical.

As i say if anyone has had a similar issue, please let me know.

Paul

 

[pvanv]

Re: 2003 Tohatsu 25hp M25c3 issues

You must diagnose, else you guess. Guessing leads to random parts swapping. That is the most expensive way to repair an outboard.To test ignition bits, you will need a good analog ohm meter. Emphasis analog. Use your factory service manual, available from any dealer, including me, as a guide to diagnostics.