impeller problem

[forenplayer]

I have a yamaha outbord motor 4hp.Is there step by step instructions available to change the inpeller?The reason i want to change it,the water from the top of the motor comes out like a spay istead of steady flow.Am i on the right track?

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[Keith]

try poking a stiff piece of fishing line up the outlet pipe, i had the same problems with my eight horse yamaha and it was a blockage in the outlet.........keith

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[forenplayer]

can i do that when motor is still in the water ?

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[cliff]

Hold on before you go poking anything anywhere. The yamaha 4 stroke 4hp had a modification on later models where the discharge is a steady stream, on the earlier models the discharge is a spray.

I have one of each model (pre and post modification) and went to great lengths to get the older one to give a steady stream like the later model only to find there had been a mod and there was nothing wrong with the older one - it is supposed to be a spray. The change over was late 2002, or so I was told. Sounds like you could have one of the earlier type and are comparing it to one of the later type.

I spent hours flushing descaler through in a small 5 gallon tank and poking and poking and flushing in a fresh water running tank (prop attached and under load in gear) nice and warm but to no avail - still a steady spray.

Changed the impeller even though there did not appear to be anything wrong with the old one - still a spray rather than a stream.

If you want to change the impeller then proceed as follows

1) Mount the engine on a stand (or on the pushpit with the leg inboard)
2) On one side of the leg you will find a large rubber bung / plug about 1½" dia - remove it by lifting the edge with a blunt flat-blade screwdriver or similar.
3) Behind the plug you will see two rods connected buy a two piece clamp with a central bolt (10mm head)
4) Note the position of the clamp and then slacken the bolt - DO NOT REMOVE the bolt. With the bolt slackened sufficiently you should be able to pop the rods out of the clamp and finally remove it (the clamp).
5) On the lower end of the leg you will see 3 bolts, one holds the anode to the lower housing and the other 2 hold the lower housing to the leg. remove the two outer bolts holding the lower housing to the leg. Be careful not to allow the lower housing to fall away yet.
6) Carefully give the lower housing a "wriggle" to loosen it and slowly lower the housing away from the leg.

You now have the lower housing / gearbox and water pump free - the pump is mounted on the top of the lower casing and you now can open it and change the impeller.

Reassembly is the reverse of the dismantling sequence, the only "technical" bit is resetting the gear linkage (the two rods clamped together).

If you noted the position of the clamp, see 4) above then you are almost there. Refit the clamp loosely, making sure the rods are in position then with the gearbox and gear lever both in the neutral position tighten the clamp.

On refitting the lower housing you may need to wriggle the tube that carries the water from the pump to the engine to get it to line up with the inlet hole but the hole in the bottom of the engine appears to have a taper on it to guide the tube into place.

Finally flush the engine out frequently in fresh water. I use an old 5 gallon rectangular water tank (think it was plastimo) with one end cut away. Fits nicely over the skeg and prop and comes well up the leg allowing me to flush about 3 gallons of fresh water through each engine while hanging on the pushpit - A couple of bits of rope tied onto the engine carry handles hold the tank up - tank is too small to run the engine in gear but running at tick over or at start position is enough. This also allows you to burn off any fuel left in the carb.. Store the engine upright or if you have to lay it down do so on the tiller side only not on its back or gearshift side and NEVER raise the leg above the engine level as the oil can run up round the engine and enter the cylinder causing a hydraulic lock next time you try to start. It is also possible for remnants of water to enter the exhaust manifold and hence get into the cylinder.


Don't think there is anything important that I have overlooked but I am sure others will have other words of wisdom to offer.




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[forenplayer]

Thank you.I better find out what year the engine is first

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