Mercruiser Engine Tips at Sterndrives.Com

Engine tip number one...... RPM, RPM and RPM!
If your not getting your proper RPM's then find out why.
Too low of RPM could be from something as simple as bottom growth or a bad prop to something as serious as water getting into a cylinder from a bad exhaust riser gasket.
Too high of RPM's could be from having the wrong or damaged prop and could seriously damage your engine!
Schedule regular service checks. I just bet that if a study was done on the amount of money spent maintaining an engine that it would expotentially reduce the amount of money spent on repairs. It only makes sense!
Your manual or service writer can tell you how many hours before your next scheduled service interval.
Typically, filters and lubes should be changed every 50 to 100 hours of use. Rubber water pump impellars should be replaced every year and exhaust elbow gaskets every two years or if they appear to be "weeping" water.
A typical check-up should consist of items such as filters, tightening belts, checking connections and hose clamps, adjusting shift and carbs, greasing steering and drive, checking operating temperatures and RPM ranges, inspecting for water and oil leaks, load testing batteries, topping off coolant levels, blower and fire extinguisher condition, as well as cleaning up any rust and corrosion.

Engine alignment is CRITICAL. If you suspect that your motor mounts have moved, come loose, or failed then have your alignment checked by a certified Mercruiser mechanic ASAP.
Running an engine out of alignment will strip-out the engine coupler and could cause damage or injury!
Engine alignment must be checked every year with the proper tool and the outdrive driveshaft splines need to be well greased with Mercruiser Spline Grease.

Cool tip..... With the engine warmed up, you SHOULD be able to hold your hand on top of both exhaust elbows without having to pull away from the heat. IMPORTANT! Make sure the engine is NOT rediculasly hot from over heating or you WILL burn your hand.
If you can't keep your hand on the top of the exhaust elbow then the exhaust is not getting enough water for one reason or another.
Another little "cool tip" is that if you see exessive or more than usual steam coming from the exhaust area then the engine may be running too hot or water is leaking into the exhaust system or cylinders.
Boats will at some time or another overheat. Weed in the intake, a worn impellar, a sticking thermastat, clogged exhaust water passages. It WILL happen sooner or later. When it does.... take precautions such as stop engine immediatly if safe to do so, perform a follow-up inspection for over-heat related damages.

This tip will save you some bucks..... Many mechanics don't know this either... If you overheat your engine then you need to remove and reseal your outdrive. Yep. Sounds like a line of crap but it isn't. The hot exhaust passing through the drive housings will melt several drive seals and may also actually melt the water pump housing on some drives. This is really important and is frequently missed or ignored leading to thousands of dollars of repairs to the drive.

Great Exhaust Tips and Replacement Procedures