Pick a New Engine | What to Look For | Making a Blank | Removing the Old Engine | Disconnecting Systems | Mounts and Coupler | Lifting the Old Engine | Engine Beds | Shimming | Filling Holes | Flat Mounts | Landing the Engine | Exhaust System | Other Systems | Finishing Up
Disconnecting the Engine Systems.
First system-Fuel
- Shut off the fuel at your tank, or drain it if that’s not possible
- Disconnect and label the return line, then the intake line.
- Coil up the hoses, plug them, and stow them out of the way, you may be able to use them without modification in the new engine.
Next system-Water
- If you are in the water, turn off the engine intake thruhull
- Remove the water intake from the raw water pump
- Plug, stow, and label the water intake hose for possible re-use.
- It may seem to be a waste to remove an existing water strainer but I haven’t seen one yet that can withstand a direct blow from a swinging 400 lb. motor.
Third system-electrical
- turn off your battery switches and disconnect a terminal so that there’s no power in the engine electrical system
- Remove the big red positive wire from the starter, label it, tape the end so it can’t zap you later and put it out of the way
- Remove the big black negative wire from the engine body, label it, tape it, and stow it
- Remove any small negative wires. Typically these are black wires that just connect to the engine body, often in completely random places from latter-day “improvements” to your boat’s electrical system. If you need 12V electricity (e.g. cabin lights) while you install the new engine, you may have to connect these to the big black wire.
- Disconnect the engine wiring harness – it may be a simple plug. This can get complicated. Worst case, cut everything and call in an electrician when the new engine is in place. Best case, label everything and stow it out of the way
- Disconnect (and label!) the alternator and its wiring. You may be able to use this on your new engine, or keep it as a spare.
- Look for any other stray wires, disconnect or cut them, label them and stow them out of the way.
Fourth System-Exhaust
- This one can be a hassle, often the big exhaust hoses don’t bend and hose clamps fight every inch of the way.
- I usually cut the rubber hose just aft of the mixing elbow. Usually have to snip the wire reinforcing with some snips. If no reinforcing, replace the hose. Consider replacing the hose anyway if it’s old and cracked or torn.
- If removing hose clamps, use a 5/16” socket, not a flat-head screwdriver. Much easier and no slipping
That should be all of your major systems in a standard marine diesel or gas engine for a small cruising sailboat. Stop. Take a look around. Is anything else connecting the engine other than the mounts and coupler/shaft? If so disconnect it. Engine driven hot water heaters, refrigeration, fire pumps, etc will all need to come off. Use what you have learned in taking everything apart so far: label everything, plug hoses, tape wires, take your time. Make a clear space around your engine – you will need it. If it can come off, take it off. You will find that a whole lot of unnecessary damage to the cosmetics of your boat can be prevented this way. A lighter motor is a safer motor and it doesn't hurt as much.
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