Mariner 75 hp, loss of power and some

scooter k

Recruit
Joined
Jul 27, 2010
Messages
1
I have a 1989 mariner 75 2 stroke on the back of my pontoon boat and I lost some power and when using throttle to go full speed it only goes up to about 3000 rpms, before I was getting 4200 rpms. Motor takes off ok , until I go to about half throttle then it bogs,If I give it full throttle rpms go up just a little,and I can feel/hear motor kind of bump but not nearly running at full power. Another problem Im having is when im using my power trim, sometimes the motor bogs down when using power trim, sometimes it doesnt. I added sea foam to gas tank,and replaced inline fuel filter,and new plugs. I backed off all the electrical connections with nut driver and re-tightened them thinking that may have been a problem. I have 2 batteries in series ,tested them ok.Can someone help?/ Thx
 

sxmerc

Petty Officer 1st Class
Joined
Jul 13, 2010
Messages
247
Re: Mariner 75 hp, loss of power and some

Sounds like you are dropping ignition to one cylinder. Probably a bad coil. Also, you should consider dropping down several prop pitches if all you were getting before was 4200 RPM. This motor should be turning 5500 RPM at wide open. At 4200 turns, you are severley lugging the motor.
 
Top