I have 2012 Tohatsu MFS4BL which has been upgraded by dealer to 6 with hi thrust prop and alternator. This is auxiliary power on 27 ft 4000 lb sailboat
I had a 2010 version of same motor for 2011 season and loved it until stolen. This motor was purchased Spring 2012 and worked flawlessly as well.
Oct 2012 finished sailing for season. Took motor to dealer for winter service in November. This service included run engine to flush, stabilize fuel system, fog engine, drain carb, change engine oil, change gear oil, spray powerhead with corrosion guard
May 2013 picked up engine from dealer. Store it upright on a motor stand. Ran in a test tank for 20 minutes at low throttle and ran properly.
June 1 2013 ran again in test tank for 20 minutes at low idle and ran properly. Went sailing and left outside so my daughter put in garage but laid it on side with handle up for 5 hrs until I got home. I then put it on motor stand upright but did not see oil on floor. The next day I ran again in tank for 20 minutes with no problems.
June 15. Launching of boat. With boat still in travel lift slings I start the motor and it starts first pull but then revs high for 20 seconds or so and then dies. Try restarting and it continues to do this. Gas coming out top end of carb. Try tapping the carb but no luck. Water flowing properly all these times.
At the dock we take carb apart and there is some dirt (I was toldf). Put back togetehr and run the motor wile docked at low idle (using external tank) and it runs well but dies after ten minutes. Go sailing and works well on way out and on way back into marina. While at low idle for docking and while in neutral the motor stalls. Will not immediately restart and this is a displacement boat so dock with more momentum than desired since no engine means no reverse. Starts up again when I try at dock but I am not happy so I take it off boat and back home.
June 16 as I remove engine from truck (travel with it on side handle side down) I see gar oil dripping out of the bottom and find that the gear oil drain screw is loose. Tighten and top up gear oild and thank myself for bringing engine home! I also replace spark plug with brand new one just to be safe. In test tank the engine continues to stall after a couple minutes at low idle so I adjust the throttle stopper screw on top of carb 1/2 turn clockwise. Runs perfectly now and does not stall. Run engine for an hour at low idle. using internal tank
June 20 run engine for an hour low idle with no issue on internal tank.
June 21 back to boat and put engine on stern. Runs at low idle at dock for 3+ hours without stalling on internal tank.
June 22 - go sailing. Use external tank (since I used 3 hours of internal tank fuel night before). Engine works well on way out - run for 10 - 15 minutes. Coming back in engine starts well and I run at 1/3 throttle while dousing sails. Stalls. No easy restart. With hood off I think I see some trace of gas on carb but no more is coming out. try tapping carb. get engine started and begin motoring in our narrow channel (no water either side). Running WOT and it sounds OK but a bit off. 2/3 of way thru channel it dies and will not restart. When I eventually get it restarted only runs at very high throttle. Dies within 30 seconds. Does not restart. get towed in.
At dock try to restart. Will only start with throttle open wide and choke on max. Will run high revs for approx 5 seconds then die down and kick and sputter three or four times then take off and run high revs. This repeats five or six times and then motor dies after 30 - 40 seconds. Does this again the next two times I manage to restart
I take motor back home again.
June 23. Again in test tank. Motor seems to exhibit same symptoms initially on internal tank. I disconnect fuel filter and drain from both ends (no visible debris) and then restart. Motor works beautifully again. Runs for 20+ minutes at both high revs and at low idle with no issues. Took a video. Can be seen here:
Tohatsu mfs4c - YouTube
I decide I have a lazy motor that does not like to puch a boat (humour)..
Dropped motor off at dealer.
Any help would be appreciated. I specifically sought out this model and configuraton for power and weight and have loved it until this year. Every time I try to use it with my boat it dies and I cannot trust it as it is now dangerous.
Mike
I had a 2010 version of same motor for 2011 season and loved it until stolen. This motor was purchased Spring 2012 and worked flawlessly as well.
Oct 2012 finished sailing for season. Took motor to dealer for winter service in November. This service included run engine to flush, stabilize fuel system, fog engine, drain carb, change engine oil, change gear oil, spray powerhead with corrosion guard
May 2013 picked up engine from dealer. Store it upright on a motor stand. Ran in a test tank for 20 minutes at low throttle and ran properly.
June 1 2013 ran again in test tank for 20 minutes at low idle and ran properly. Went sailing and left outside so my daughter put in garage but laid it on side with handle up for 5 hrs until I got home. I then put it on motor stand upright but did not see oil on floor. The next day I ran again in tank for 20 minutes with no problems.
June 15. Launching of boat. With boat still in travel lift slings I start the motor and it starts first pull but then revs high for 20 seconds or so and then dies. Try restarting and it continues to do this. Gas coming out top end of carb. Try tapping the carb but no luck. Water flowing properly all these times.
At the dock we take carb apart and there is some dirt (I was toldf). Put back togetehr and run the motor wile docked at low idle (using external tank) and it runs well but dies after ten minutes. Go sailing and works well on way out and on way back into marina. While at low idle for docking and while in neutral the motor stalls. Will not immediately restart and this is a displacement boat so dock with more momentum than desired since no engine means no reverse. Starts up again when I try at dock but I am not happy so I take it off boat and back home.
June 16 as I remove engine from truck (travel with it on side handle side down) I see gar oil dripping out of the bottom and find that the gear oil drain screw is loose. Tighten and top up gear oild and thank myself for bringing engine home! I also replace spark plug with brand new one just to be safe. In test tank the engine continues to stall after a couple minutes at low idle so I adjust the throttle stopper screw on top of carb 1/2 turn clockwise. Runs perfectly now and does not stall. Run engine for an hour at low idle. using internal tank
June 20 run engine for an hour low idle with no issue on internal tank.
June 21 back to boat and put engine on stern. Runs at low idle at dock for 3+ hours without stalling on internal tank.
June 22 - go sailing. Use external tank (since I used 3 hours of internal tank fuel night before). Engine works well on way out - run for 10 - 15 minutes. Coming back in engine starts well and I run at 1/3 throttle while dousing sails. Stalls. No easy restart. With hood off I think I see some trace of gas on carb but no more is coming out. try tapping carb. get engine started and begin motoring in our narrow channel (no water either side). Running WOT and it sounds OK but a bit off. 2/3 of way thru channel it dies and will not restart. When I eventually get it restarted only runs at very high throttle. Dies within 30 seconds. Does not restart. get towed in.
At dock try to restart. Will only start with throttle open wide and choke on max. Will run high revs for approx 5 seconds then die down and kick and sputter three or four times then take off and run high revs. This repeats five or six times and then motor dies after 30 - 40 seconds. Does this again the next two times I manage to restart
I take motor back home again.
June 23. Again in test tank. Motor seems to exhibit same symptoms initially on internal tank. I disconnect fuel filter and drain from both ends (no visible debris) and then restart. Motor works beautifully again. Runs for 20+ minutes at both high revs and at low idle with no issues. Took a video. Can be seen here:
Tohatsu mfs4c - YouTube
I decide I have a lazy motor that does not like to puch a boat (humour)..
Dropped motor off at dealer.
Any help would be appreciated. I specifically sought out this model and configuraton for power and weight and have loved it until this year. Every time I try to use it with my boat it dies and I cannot trust it as it is now dangerous.
Mike
