DIY boat repairs:

changing an Outboard water pump

Sometimes outboard motor water pumps give up the ghost in the middle of the season, when service technicians are swamped. You could miss two or three weeks worth of boating waiting for repairs. Or you could do diy change the outboard water pump. The good news is any reasonably competent Do-It-Yourselfer own can get it done in about two hours. Here are the basics.

Begin disassembly by removing the bolts that fasten the lower unit to the midsection. Disconnect the shift linkage. Slide the two housings apart. If they won't pull apart, look for any bolts you may have missed.

Saltwater motor housings may have corroded together and stubbornly refuse disassembly. Never use force. Just get a bigger hammer. In this case your hammer is an oxy-acetylene torch. Unfortunately the common propane torch doesn't put out enough heat. Warm the parting line. Then let it cool for an hour. Heat it again. Let it cool. Heat expands aluminum. Cooling contracts it.

Growing and shrinking breaks the corrosion allowing removal. If you must hammer the cases apart, use a rawhide mallet, not a ball pein hammer. Otherwise the cases will crack. If you can;t split the cases, take them to a dealership and have it do the dirty work.

Once the cases come separate, look for any bronze locating pins that align them. Some motors have them. Some don�t. Save the gasket if there is one. It prevents corrosion from gluing the case together.

Remove the four or five bolt that secure the water pump housing to its base. Lift off the housing, the impeller and the thin, stainless steel base plate. You will likely find a bad impeller, one with stiff and/or missing blades. Examine the base plate and inside water pump housing looking for scoring caused by sucking sand up through the system. Either way replacing all the components now is cheaper than redoing the job six months later.

Some drive shafts have an O-ring on the crankshaft end that slides up into the engine. Shine a flashlight inside the motor, making sure the old one isn�t lodged inside the recess if the crankshaft internal spines.

Grease the drive shaft splines.

Carefully align the water pump tubes and slide together.

Reattach the shift linkage.

Coat the threads of the bolts with anti-seize compound to make subsequent disassemblies easier.

Do not make the mistake of over tightening the bolts or you risk stripping the threads. Final due diligence, check the gear case oil, looking for any sign of water intrusion. If the seals are bad, now is the time to replace them.

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