Sold a 5 year old cruiser tradein,twin Mercruiser v-6's,subject to survey. Don't know boat's history,but it was low hours and very clean. Oil analisis(sp) from surveyor showed one engine with PBT,surveyor said that showed engine had been apart. Also showed 90 parts per million iron,he said 30 was maximum,this means a bearing is going to fail soon. This is a respected surveyor,buyer is convinced that he should replace that engine immediately. Unfamilar with all this,is this a valid conclusion. Can that much specific info be learned from this?

Ive always been under the impression that one oil analysis doesnt mean a whole lot. If an analysis is done at every regular oil change a pattern can be established and unusual changes can be a sign of impending problems. Hopefully, someone else will chime in here. I'd be very suspect of a one time analysis making a call like that.

I would think that iron would be more like a cylinder going bad, not a bearing. I use Blackstone Laboratories for analysis. You could probably get better information by reading at their site. Click on their different sections including marine to get an idea of what problems are indicated in different sample reports.

http://www.blackstone-labs.com

zahndok is right Iron is clyinder wall not bearing material, bearings are made of a variety of materials but the one thing they all have in common is that they are non ferrous and cast iron does not fall into that category. Also one oil smaple is not sufficeint to tell the whole story. while 90 ppm of iron is out of narmal range it could just be due to the oil not being changed recently enough, if you have run 2-3 times the normal drain interval then the #'s will reflect it. This isn't a good thing either but its better then what the surveyor is suggesting. If it was youre personal boat I would recomend an oil change and crankase flush, then running 50 hours or so and taking another smaple and seeing where you stand then. you may find there is nothing wrong other then the accelerated wear cuased by extended oil change intervals in the past.

I agree about the 1 time oil check and its the cly,but the iron could be a spund bearing(I dought it) or parts of an oil pump(dought that too) ,any part that touches iron .

http://www.oilfax.com/

One would need more data:

-Hours between oil changes

-Type of oil used

-Type of oil fliter

-How hard the engine was run

-# of hours...

But it does sound like something is showing wear.