Read bwfa07.EN.Outboard.qxd text version

ENGINES

SKILL LEVEL

EASY HARD

TIME

16 HOURS (ONE DAY TO TAKE IT APART, ANOTHER TO PUT IT BACK TOGETHER)

OUTBOARD REBUILD

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UPPER-UNIT DISASSEMBLY

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After wiping off the motor with a wet rag, we got down to business-- draining any remaining gasoline from the fuel tank and oil from the gearcase. Using a vise, we clamped the engine to a workbench and removed the side panels. Next we disconnected the spark-plug wire and pulled the spark plug. It was covered with soot, but was otherwise in good condition, so we cleaned it off for possible reuse.

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With the control panel off, we were able to disconnect the stop-switch leads, capacitor discharge ignition (CDI), and remaining electric wiring. All wires were color-coded, so reassembly was a snap.

OUTBOARD REBUILD

Who knows how long it had been sitting in the garage. When we took possession of the 1989 Yamaha 2-stroke, 2-horsepower outboard motor, it was unused, unloved, had seized up, and was collecting dust. We had no idea what we'd find under the proverbial hood and weren't certain it could be repaired. While our expectations were low, our assignment was simple:Take the engine apart, diagnose its problem, and get it running again--and hopefully have a little fun in the process. In the end, the project took two full days and cost around $70 for a complete set of replacement gaskets, O-rings, oil seals, impeller, and new water-pump housing. Other parts also might have benefited from replacing, but we took a wait-andsee approach with these. We could always swap them out later if the motor actually worked. We used just basic tools-- wrenches, sockets, screwdrivers, and pliers--with a few extra items like lubricant, a hammer, Vise-Grips, and some sandpa-

CHECKLIST

TOOLS

Basic tool kit Wrenches and sockets (metric if you're working on a European or Japanese engine) Screwdrivers Propane blowtorch Rubber mallet Hammer Razor blade Pliers Vise-Grips Vise 400-grit wet/dry sandpaper Brush for applying grease and lubricating oil Torque wrench Outboard-engine manual

Seized motor? Don't be so quick to junk it. With a little time and the right spares, you can bring a dead outboard back to life By Dave Baldwin

per. We also bought an illustrated shop manual--many of these are available from Internet book sellers--that proved invaluable. Finally, the photos we took to document this story came in handy when we put the engine back together. If you have a digital camera, take some snaps along the way; you'll be happy you did.

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MATERIALS

At minimum, a new set of gaskets, but other spare parts may be required Waterproof grease (make sure it's graphite-free; graphite can corrode engine components) Oil-gasoline mixture Kerosene Penetrating oil

30 BOATWORKS | FALL 2007

PHOTOS BY MARK CORKE

ENGINES

4

We took off both the recoil starter housing and the fuel tank (after detaching the fuel line from the carburetor), although we decided not to disassemble the starter and flywheel before further inspection (it can often be left intact). Disassembling the flywheel may require special tools.

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So far, so good. Next, we removed the cylinder head and inspected the piston, finding it in good shape. We lubricated the piston, but the flywheel still struggled to turn.

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Off with the carburetor, reed valve, and intake manifold. Surprisingly, the connecting rod also looked good, so we kept our fingers crossed and hoped the problem might lie outside the motor. After a significant struggle that required the use of wooden wedges, we disconnected the power head from the drive shaft housing. Eureka moment number 1. The flywheel spun while the piston and rod moved freely. We sprayed more lubricant inside to loosen them up further. The propeller, on the other hand, still wouldn't turn despite being freed from the motor. We were getting warmer.

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TOP TIP

We put all nuts, bolts, screws, and washers into carefully labeled plastic cups for easy access during reassembly.

LOWER-UNIT DISASSEMBLY

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First we pulled the propeller cotter pin and detached the propeller before sliding the entire lower unit out of the driveshaft housing. With the lower unit now clamped to the bench, we removed the carrier and gasket, but inspected only the propeller shaft and gear. They looked fine, so we decided against taking it all apart.

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We extracted the drive shaft from the drive-shaft tube and found it to be rusted as well. Clearly, water had been circumventing the seal and entering the driveshaft tube rather than exiting via the waterpickup tube. Careful examination later revealed that someone had crimped the drive-shaft tube in order to get it back into the water-pump housing.

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Next we opened and disassembled the water pump. Eureka moment number 2. What a mess. Only two of the six blades remained on the impeller; bits of the other vanes fell to the floor. The inside of the pump housing was rusted and the oil seals were damaged. Both of them prevented the drive shaft from turning. Houston, we have the problem.

FALL 2007 | BOATWORKS

31

OUTBOARD REBUILD

ENGINES

OUTBOARD REBUILD

REASSEMBLY

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After ordering replacement gaskets, oil seals, and a water-pump housing, we organized all engine parts on the workbench. Using a propane blowtorch and hammer, we detached the driveshaft tube from the corroded waterpump housing. Since the end of the tube had been crimped, we used a piece of rod rigging to force a socket of equivalent diameter through the tube, thus reshaping it to as close to original as possible. This worked as a jury rig, but it would have been better to replace the tube. NOTE: A propane blowtorch can be helpful in removing rusted or stuck parts, but be careful--it can cause irreparable damage.

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The 1989 model of this engine has two oil seals inside the water-pump housing. We fitted a new Oring into the top of the housing (it slides into an interior groove) and brushed it with oil. Then we lubricated the inside and inserted the two oil seals, using a socket to press them completely into place.

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We sanded the rust off the drive shaft and covered it with waterproof grease. After shooting a generous amount of grease into the drive-shaft tube, we reinserted it through both the tube and the water-pump housing.

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With the impeller drive pin inserted into the drive shaft, we slid on the new impeller and reinserted the drive shaft into the gear case, attaching with bolts properly labeled in the plastic cups. IMPORTANT: Make sure the impeller is inserted with the vanes bent in the direction of rotation. If not, it will have difficulty turning, the blades could break off, and the pump won't work.

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Next we reassembled the gear case with a new gasket and carrier and attached a new sacrificial zinc anode to the bottom (compare the new and old anodes). Then we reinserted the gear case--with brass water-pickup tube attached--into the drive-shaft housing. We're halfway home.

32 BOATWORKS | FALL 2007

ENGINES

16

Using a razor blade and a vacuum cleaner, we scraped the old gaskets off the exhaust plate, drive-shaft housing, and cylinder head. Next we inserted a new Oring into the exhaust plate and brushed it with oil. After inserting the new gasket, we reattached the cylinder block. Working from inside out, we tightened the cylinder block in equal amounts until reaching the final specified torque of 7 ft-lbs.

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With the cylinder head scraped, we attached the new gasket and rebolted it to the cylinder block.

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At this point, we were simply working in reverse order. The reed valve and intake manifold were attached to the crankcase next, and we made certain to first insert a new gasket.

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Next we reattached the carburetor to the intake manifold, fuel tank, and manual recoil starter assembly. Don't forget to reconnect the fuel line.

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Now for a quick test of the spark plug. Pulling the starter cord, we got a spark to jump across. This plug is still good, but we would have installed a new one had we remembered to buy one.

GEAR CASE & WATER PUMP

1. Drive shaft 2. Pin 3. Water tube 4. Seal 5. "O" ring 6. Water pump housing 7. Oil seals 8. Plate 9. Impeller 10. Liner/seal protector 11. Seal 12. Cavitation Plate 13. Dowel pin 14. Bushing 15. Gearcase 16. Vent plug 17. Drain plug 18. "E" ring 19. Pinion gear 20. Thrust washer 21. Shim 22. Bearing 23. Shim 24. Shear pin 25. Propeller shaft & gear 26. Gasket 27. Carrier 28. Oil seal 29. Propeller 30. Cotter pin

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Almost there. We reattached the control panel, replaced the covers, bolted the handle back on, and remounted the propeller and shear pin. Then we filled the gearbox with oil (shooting the oil up to force air out) and the tank with a 50-50 gas/oil mix. And now the moment of truth. After several minutes of pulling the starter cord, we finally got contact. A whirl of smoke fumed out, and it started purring like a cat. Success never felt so good. This motor is back in business. BW

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ILLUSTRATION BY PAUL MIRTO

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GO TO SAILMAGAZINE.COM/BOATWORKS TO SEE MORE PHOTOS

FALL 2007 | BOATWORKS

33

OUTBOARD REBUILD

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