Tohatsu 9.8 two stroke, starts well, no power

PJT · 03 September 2014, 17:08

Hi,

Just bought a very clean 2006 Tohatsu 9.8 2 stroke with low hours. No power though and sounds like off a cylinder when reved

Starts easily.
Idles well.
At low revs, sounds perfect.

Out of gear
- up to half throttle, revs climb steadily and sounds perfect.
- up to full throttle, revs high and then revs drop, does not stall. Sounds like off a cylinder....

In gear/under load
- revs to about 25%, giving out not much power......1980s 4HP is faster :-)

So far (with no difference)
- New fuel always used
- Carb cleaned x2 (perfect)
- New plugs

Something electrical perhaps ?

Advice much appreciated. Thanks.

slate1234 · 03 September 2014, 19:26

take one plug lead of and see if it starts (dont run for to long) check fuel filter engine side and filter in the fuel tank when you say clean carb have you soaked it for 24 hours in cleaner with everything removed ?? electrical could be a coil, cdi, leads, have you checked that both plugs are sparking??

slate1234 · 03 September 2014, 19:29

9.8hp on a 4m+ now that's hoping

m chappelow · 04 September 2014, 00:45

I had same problem with a near brand new Tohatsu a few years ago 10 hrs running ,
Turned out to be a crack on a spark plug ceramic insulator , it would start ist pull & run fine upto 3/4 power then it would drop off & go onto one cylinder , at first without really close inspection the plug looked fine , but what was happening is the broken insulter was vibrating up & down down the electrode shutting the spark off the tip then was shorting out back up inside the plug .
New plug & has been right ever since ,, though you did say earlier you had replaced the plugs ?

PJT · 04 September 2014, 09:31

Thanks for advice. Will investigate further

Nightfisher · 10 September 2014, 09:37

Switch box, loose magneto or Mag connectors or bad coil. Start by tightening Switch box after sanding off any rust or corrosion to where box attaches to block ; same with both coils. Look for cracks in insulation of both plug wires. When it does giving problems. Shut-down check each plug see if one is wet with fuel. If one is, 1/2 the battle is done if repairing it.