I bought this engine in 1995 and since that time the temperature reads between 140 to 160 when the boat is planning and close to 200 when trolling. The engine I had before was an OMC and it always keep the same temperature when either cruising or trolling. I always thought this was normal functioning for the Mariner since I bought it new but now I am wondering. <br /><br />After 10 years of regular performance although it never left me stranded I had to replace 2 switchboxes, 2 regulators, injection module when bad twice (the second time I bypassed it so now I premix the oil) , and the idle stabilizer also when bad. This year the stator finally broke leaving my 15 hp kicker doing the hard work to get back. After removing the flywheel I found out the trigger show cracks and ohms readings were off.<br /><br />I already ordered both parts but I like know if a temperature near 200 when trolling is normal for this engine . I understand that eventually these electrical parts sooner o later may go bad but I am concerned that overheating may be causing them to go bad sooner.<br /><br />thanks
<br /><br />When the module went bad and you started premixing did you disable the oil injection? The pump is mechanical and has nothing to do with the electronic module working or not. But that's not what you're asking.<br /><br />If you've never had the water pump rebuilt, it's long past due. The manufacturers advise rebuilding it every year, but every 3 to 5 isn't unreasonable. After 5 you're on borrowed time. You might also consider cleaning or replacing the thermostats (assuming this is a V-6 150). They can scale-up and stick. A soaking in vinegar is usually sufficient. That motor bypasses the thermostats at higher RPMs. That's why it's running cooler at higher speed and hotter at trolling. Sticky thermostats could cause that motor to be running hot at low RPMs.