s200TXRU Yamaha flat spot/ hesitation - The Hull Truth

ducman851 · 09-21-2008, 08:26 PM

I seatrialed a boat with the above Yamaha 200. Started fine, idled fine, holeshot was fine and pulled to 5000 rpms with hestitation. When I backed off the throttle to cruising speed of 3400 rpms and then accelerated there was a marked hesitation or flat spot before the motor responded. Each time I tried that same sequence it hestitated regardless of rpms. Any suggestions? Motor has low hours(200+) and according to the owner has done that the entire time he has owned the boat...5 yrs. He has taken the boat offshore and had no other problems accept for the hestitation.

A1 Outboard · 09-21-2008, 11:07 PM

That 1996 motor usually performs better if it is propped closer to 5500 rpm. I'll bet a one size change in prop pitch (smaller) would make a world of difference.

Because the S200 has different tuning specs than the other 200 models that year, perhaps the WOT timing is set wrong, 21° vs. 20° for the regular 200. There may be a throttle linkage adjustment that is not correct also. If the diaphragm fuel pumps haven't been changed in a number of years, go ahead and do that automatically just to be on the safe side. There is a chance that carburetor cleaning may be needed, but I kinda doubt that from your description on how the well the motor runs otherwise.

It might be a good idea to have a Yamaha trained technician check over the motor completely, paying close attention to the adjustments and the condition of the fuel system. Of course a compression test should be done first to see how the internal condition of the motor is.

ducman851 · 09-22-2008, 03:37 AM

I meant to say that the motor works fine from trolling speed up to WOT without hestitation. It seems to hestitate only after the boat is on plane and I pull back the throttle and then open it up again...that's when it flat spots or hesitates. I will have the local yamaha mechanic check it out.

Thanks!