Re: Tohatsu Seized 9.8 HP 4 stroke
Assuming you ran the motor in water, and didn't wreck the impeller, the next thing would be to fill the oil and check the LU lube, and try a test fire (in water or on muffs, of course) to see if it does run. Otherwise, put a new impeller in before you go further.
If it does run, there will likely be less compression than new, but it MAY work OK. Probably will use oil more than usual, especially until the rings re-seat. If it runs, it will probably dump more heat than usual while the cylinders mate up to the rings.
Assuming it does run, listen carefully for connecting rod noise. If it has a rod knock, it will need to be torn down. If it sounds normal, I would just run it, and keep an eye on temperatures and oil consumption. If it got bloody hot as it seized, the thermostat may have jammed, so monitor cooling closely.
The 8/9.8 does not have bearing inserts at the big ends of the connecting rods, so a rod knock may call for a new crank and rods. The specs are in the Factory service manual. If you have micrometers (both inside and outside mics) and plastigage, and the skill to go through the bottom end, an R+R of the rods and crank is do-able, and still cheaper than a new motor. If you DO have to tear it down, consider honing the cylinders, and throwing in a set of pistons and rings (and possibly an oil pump) along with whatever bottom end parts it needs, while you have it apart.
Otherwise, if you have a rod knock, and can't overhaul it yourself, it will be time for a dealer estimate to determine whether repair or replacement is more economical
If it fires up OK, and doesn't knock, count your blessings, and just run it.
It will never be "new" again, but you may have gotten lucky, and gotten one that will run.
