Small Engines (Lawn Mowers, etc.): Lawn tractor starter trouble, jumper cables, drive belts

Question
I have an MTD with a 17 hp Tecumseh.  For 4 years, since the warrantee expired, the Starter has trouble turning the engine.  I've replaced battery, starter, cleaned all connections.  I have to manually move the flywheel back from the compression to give the starter time to pick up speed to get past the first stroke.  It is as if it needs more amps.  Jumper cables hooked to a car battery will give it the extra boost it needs.

The starter rebuilder says the starter appears to small for that engine. The starter is factory specs.

Any Ideas?  

Answer
The size of the starter is not necessarily indicative of its torque output.  I would make sure that nothing is dragging on the engine (drive belts, etc.) and causing it to be more difficult to turn over.  If nothing is causing unnecessary drag, I recommend that you find someone (or a shop) that can put an inductive ammeter on the starter cable when you try to start it.  If it is drawing excessive current (more than 75A), there is a problem with the starter.  Because you can hook the booster cables directly to the battery and the engine turns over properly, there should be no issue with the cables, solenoid or connections and suggests there is an issue with the battery instead.  If this is the case, I recommend you fully charge the battery and have it load tested by a shop to determine its condition (sometimes new batteries can be defective).  Hope this helps.