Originally Posted by actions
I have a 30hp Mercury 2 stroke 2003 engine. I am looking at getting this fully serviced, winterised and a new impellor at the end of October (will try and get a few more days out yet), but would be keen to know what sort of price i would be expected to pay for this.
I would have a go myself but i wouldnt know where to start to change the impellor.
Would be grateful for a rough price guide for all the work and if anyone could tell me where to start on the impellor as a DIY job or should i leave it to the experts.
You really should have a go yourself. In my opinion the more hands-on you are, then the more aware you are of your own engine and can see tell-tale signs before any problems arise. If you're not comfortable with this - then put it to a marine engineer who you trust.
First off, order a genuine impeller. Ideally they need to be changed every other season, depending on usage, however I do mine annually. With the leg in the raised position and the engine in neutral, undo the 4 nuts on the anti-cavitation plate. There's normally a 5th nut hidden under the sacrificial zinc anode or trim tab. Undo and you'll find it. Not sure with Mariners, but sometimes you need to undo a shift-rod nut.
With all the bolts undone, use a rubber mallet and lightly tap the anti-cavitation plate at regular intervals. The lower leg should drop down. With the leg off, inspect the mid-section for any corrosion. Use a brass-bristle brush to remove any salt build up and use a mild detergent to wash off. Now the impeller. Undo the bolts (normally 4) on the water-pump housing. The water-pump will lift off to reveal the impeller. Pull the impeller off the drive-shaft. Take care as there is a half-moon steel shaped grommet (that locates in the drive-shaft.) With the old impeller off, thoroughly clean the water-pump bell housing. There will be a rubber 'o' ring gasket in the recess of the bell-housing. Remove and clean. Any deterioration - then replace. Use a little Yamlube to lubricate before refitting. Double-check the stainless-steel faceplate the impeller sits on is corrosion free. Any dis-colouration can be removed with a little wire wool and WD40 to lubricate. If it's damaged - order a water-pump kit, including gaskets, etc.
With the leg off you should also renew the gear oil. Ensure leg is in vertical position. Undo the gear oil cross-head screws on the leg. Undo the top screw first, then the drain screw. The gear oil should be like honey. If it's cloudy or opaque, then it's emulsified (water has mixed with the oil), then water-pump gaskets need to be renewed as a matter-of-course. Allow to drain. Use latex gloves as gear-oil stinks. Use Yamlube or similar gear oil to refill. Normally need two to do the job. Insert nozzle in the drain hole and pump the contents into the gear case. Once the gear oil starts to come out the top screw, place finger over the hole and then insert the screw. Now insert top screw. Double-check the gasket washers are in good condition on the screws. If in any doubt - replace.
Back to the impeller. With the old impeller removed, clean the drive-shaft thoroughly. Use Castrol marine grease (again - wear latex gloves) and lubricate the shaft, especially the splines at the end of the shaft where it locates with the powerhead. Place new impeller in the drive-shaft and pull down. It should locate with the half-moon steel grommet. It should be lubricated lightly with a little Castol marine grease. Lightly smear the water-pump bell-housing with Castrol grease and pull it down the drive shaft. Turning the drive-shaft clock-wise with the impeller in place, push the bell-housing water-pump housing into place. Ensure everything lines up before tightening. Do not over-tighten water-pump bolts.
Connect the lower leg again, and the shift-rod nut (if applicable). Do not over-tighten the bolts on the anti-cavitation plate. Apply 75Nm of force of torque, tightening diagonally at intervals before final torque specification.
Ensure engine goes into gear, forward and reverse. Add water-muffs and start the engine. She'll pee like a shire-horse! Open a can of Caffreys and enjoy the moment.