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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 14181
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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After buying new yanmar 6lp stp2's in 2011 they ran well

Customer Question

hi james.. after buying new yanmar 6lp stp2's in 2011 they ran well (other than turbo exhaust bend fatigue) until august last year when upon realising that exhaust smoke had entered the engine I ended up replacing the turbo (upon advice) to help solve the problem. Then after a trip from samoa to tokelau (700mls return), the valve bridge on the number 6 valve on the port motor gave way and the valve flew into the piston. I then had the the valve and piston replaced.. the motor then ran very well for 3 charters.. then at the end of the third charter back at the marina as we were winding down ter was a puff of smoke and the port motor seized. I then had the crank shaft replaced only for the engineer to realise that the block at number 6 was warped. I then sent the block to nz and had it re bored. The engine is now rebuilt, but we are having problems with power when under load. We are also getting diesel and lots of smoke coming from the port exhaust. We have given the after coolers (heat exchange} a very good clean but no luck.. After spenging 40k with absolutely no result, I am at wits end... Any ideas onhow we can fix the problem and what may be the cause. Being out here in the middle of the pacific any help is sincerely appreciated.
Thanks mate....Greg
Submitted: 4 months ago.
Category: Boat
Expert:  Jason replied 4 months ago.

Hi Greg, my name is Jason.

I read everything that you wrote. What kind of questions did you have for me?

Expert:  Jason replied 4 months ago.

Hi Greg. Did you have any questions?

Customer: replied 4 months ago.
Hi jasonThanks for your reply.After reading the basic history of this motor in my previous email, my direct questions are following:1 What could be causing the diesel discharge out of the port motors exhaust?
2. What could be causing the large amount of smoke.
3, What could be causing the lack of power (after rebuilding the motor it was bench tested and ran perfectly. It was not until the motor was back in the boat and under load that it has no power)
4 The best method of cleaning the after coolers of exhaust residue. (due to the badly designed turbo exhaust elbow it has perished and broken on a couple of occasions, allowing exhaust smoke to escape into the engine room and then sucked back into the engines.. We have replaced the air filters on each ocassion and cleaned the after coolers many times with de greaser .. What is the best and most effective way to clean them?
Expert:  Jason replied 4 months ago.

Hi Greg,

Low engine compression would cause all of the symptoms you have been describing. Has the engine been compression tested yet? If yes, what are the numbers?

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