[K1W1]

Originally Posted by Capt J

You're not working on 3506's if they're 850hp.......

CAT have never made a 6 cylinder 3500 Series engine that I have seen, read about or been told about.

Originally Posted by Capt J

It sounds more like 3406's possibly. A rubber impellor's service intervel on that motor is every 500hrs. 1500hrs on a rubber impellor is extraordinary.

When I used to run 3306 Gensets which have a Rubber Impeller pump very similar to the 3400 Family the service manual used to say to inspect the Impeller at 2500 Hrs, there was always cracks in the Impeller by 2000 Hrs so I developed a routine to change them at 2000 Hrs and subsequently never had a failure.

Changing them every 500 Hrs is a waste of the Owners money, if they are failing that quickly there is an external reason as to why maybe restricted inlet starving them water supply or working way beyond their design discharge pressure or shaft rotation speed.

The 3500's and others require a Valve Lash check at the first 1000 Hrs and then every 2000 Hrs thereafter. The Engines with the deep sump can also do 1000 Hrs between Oil Changes but an SOS and Coolant Test should be done every 250 Hrs to make sure you are not missing any changes that are the precursor to major problems further along the track.

Fish- How many cylinder heads does this CAT Engine you are working on have?

[Capt J]

K1W1, things are different on a generator that is running 24 hours a day 7 days a week. The average usage a yacht sees in the US is less then 200 hours a year. We mostly change impellor's because of a time issue, I think most are recommended to change every 2 years or X amount of hours. It would take the majority of private yachts in the US over 10 years to accrue 2000 hours. Also most owners would rather change wear items ahead of time then risk suffering a failure of any kind that would hamper that once every 2-3 month trip.....

I have seen a lot of impellors in US boats in bad shape at 500 hours. Cracking where the vane meets the body of the impellor and such. Missing teeth, etc.....Most of the CAT raw water pumps only last around 1,000 hours here in private yachts before they start leaking where the shaft goes into the housing......

A genset that runs constantly maintains the same rpm, and the impellor runs and runs...... On a yacht everytime you start it when it's been sitting for 2 weeks, the impellor pretty much has to prime itself and so forth....... Also the rpm's are not constant and go up and down. I don't know of anyone that has gotten 2000 hours on an impellor in a main. Some area's are worse, if you run a yacht in the Mississippi River, you're changing water pumps every year because the silt in the water just grinds them away.

Also all of the main propulsion C18's that I've worked on here in the US use a rubber impellor, all of the CAT's up to and including the C32 ACERT's as main propulsion use a rubber raw water impellor (that impellor is around $300US last time I bought one). This I know for a fact. The C32 impellors in the manual call for an inspection at the 500hr service along with oil change, zincs, SOS, coolant test (the extended life coolant usually only goes 2 years and supposedly according to my CAT guy the regular CAT coolant is better, CAT has had problems with scale and the extended life.) I am not familiar with large generator sets that are sea water cooled, CAT may be using a metal impellor in those........but definately not in the main propulsion engines, I think it has to do with the constant change in rpm's.