I just bought my first boat!!! It is a 1976 cobia 14 foot tri hull. It has a 1976 Johnson Seahorse 70HP outboard engine.
The guy I bought it from had the engine serviced back in July. He gave me the receipt for the work, and this is what was done on the boat...
"Checked engine compression- 120 on all cyls.
Checked Gear oil- dirty but no water in housing
Installed new cable ends for starter
Attempted to run engine, engine will not run
Changed gear oil
Carbs were dirty and needed to be cleaned.
removed carbs disassembled and soaked.
rebuilt carbs with new kits.
R/R water pump with kit.
Started engine after rebuilding carbs and found voltage regulator not working properly and engine running hot.
R/R voltage regulator and changed thermostat and gasket.
started engine, Engine did not run hot on shop hose and charging system is working properly. needs lake test
NEW PARTS INSTALLED: starter, carb rebuild kits, water pump kit, voltage regulator, thermostat kit, gear oil, fuel pump kit"
The engine starts, idles and shifts great. It sounds like it is running well. The boat accelerates nicely as I increase the throttle, however when I get to about the 3/4 throttle position, the engine lurches a little and going any further on the throttle does not increase engine power. It's like the boat is stuck at 3/4 power. When the throttle is positioned exactly at 3/4 the engine actually has slightly more power than at 100% throttle.
My max speed calculated by GPS is 25 MPH
I would GREATLY appreciate any help!!!!!