This is for any of you with the "Know". A month ago, I purchased a
bass boat with a Mercury Force 70 hp motor with approximately 30 hours
of run time. I was told by the original owner that the gas was at
least a year and a half old. I took my new (used) boat to the lake
and launched it. After squeezing the bulb a few times the motor
started perfectly. I left the launch dock and proceeded to put it
through its paces. The boat and motor functioned perfectly...even the
trolling motor (but that's another story). My wife and I spent much
of the morning turning 4000 rpm up and down the lake. In the early
afternoon, about two forty-five we headed back to the boat launch.
There was a waiting list of boats both being launched and retreaved so
I waited with the engine either at idle or in forward at low rpm for
my turn. The engine started to labor and then died and would not
re-start. I was now "dead in the water". No engine and no trolling
motor (that other story). With the 5 mph breeze, I was now drifting
towards some boats that were tied up at the dock. Their owners were
nice enough to push me away and left me drifting to some children
swimming in a small cove next to the launch. After beaching the
boat, I hiked to the launch for assistance from the life guard. A
boat was sent to tow me to the launch. After getting it home, I
posted here on Google about old gas and I subsequently siphoned out
all of the old gas; about 12 1/2 gallons. I removed, cleaned and
re-installed the three spark plugs. This past Thursday, I put 12
gallons of 89 octane into the tank and added 31 ounces of 2 stroke
oil. On Friday I attached the "ear muffs" to the engine, started the
water flowing and started the engine to let the "New" gas get to the
engine. The engine ran fine at idle as well as up to 1500 rpm, though
there seems to have been insufficient water flow because the engine
heat buzzer started. I shut down the engine and put my toys away.
This morning I took the boat back to the lake. It started without
problem. It turned 3500 - 4000 rpm with no problem. It idled (in
gear) for five minutes...No problem. On my way back to the launch
from the other side of the lake, I was in a "No Wake" area so I
started the engine and with it in gear, I proceeded toward the launch
turning about 750 -1000 rpm. Within five minutes it labored, stalled
and would not re-start-AGAIN. A very nice fisherman, towed me back to
the launch. This time the trowling motor was functioning and I was
able to get the boat to the dock. It now sits in front of my
motorhome, next to my house.

Question: Besides buying a different motor, what do you thing could
be causing the motor to labor and stall and not re-start? I am
prepared to take it to the local boat mechanic and have them do a
tune-up.

----A tune-up. I think I'll name the boat "TUNA-P"

Please....Your thoughts and suggestions.

Thanks from the Skipper of the "Tuna-p"