|
|
|
Quick
access to our main sections
|
Raw Water Impeller Failures We have experienced a very high failure rate of impellers on our 1997 Maxi 34 fitted with a MD2030B engine. Having lost 4 impellers in 15 months (approx 150 engine hours) we were at a loss to explain what was going wrong. Initial thoughts were that we were picking up debris so we installed an inlet filter. Although the filter was trapping barnacles and other debris, the impellers continued to fail.
1 Impeller 2
Cam 3 Cam Screw
The cover plate was in good condition and not badly scored or pitted. The only other possible cause of the impeller failures was the cam in the pump housing. It is virtually impossible to check the cam in situ, so I removed it by undoing the cam screw on the right hand side of the pump. The cam face was worn slightly, but more importantly there was quite a sharp edge on the leading edge. As a temporary measure (we were in St Peter Port) I used some emery paper to radius the sharp edge and also ensured the trailing edge was smooth. I then reversed the cam through 180 degrees before refitting it. When we got back to Poole I fitted a new cam of the correct thickness, having first given the leading edge a light emery. The impeller has now done 57 hours and is still in good condition, which is a lot better than the previous one which lasted less than 10 hours. My theory for the high failure rate was that the sharp leading edge on the cam was trapping the web of the impeller and ripping it off. If you fit a new cam ensure it is the correct thickness. There are three different thickness cams for this pump. The “replacement” cam (Johnson No 01-45288) that I was supplied in St Peter Port was a 2/3rd cam approx 4.5 mm thick where as the one in our pump was a full cam (Johnson No 01-42389) and approx 6.0 mm thick. Here are some tips if you are going to check the cam in your pump; 1. The screw that holds the cam in the pump body is a different thread to the six face plate screws, so keep it separate after removing it. 2. Replace the cam screw, when I tightened up the screw it sheared off in the cam as the tip of the screw had corroded. 3. When the cam has been fitted back into the pump body, check that the cam screw is not protruding above the cam face.
18 Apr 2007 |
Disclaimer: Whilst every endeavour has been made to ensure the accuracy of the content presented on this web-site we cannot be held liable for any consequences whatsoever resulting from the information or advice provided. Send mail to
Maxi Owners Association with
questions or comments about this web site.
|
