Thanks for the replies they are all helpful.
I had a mechanic
look at the engine last week and he has identified that the centre cylinder is week.
Not pulling its fair share of the load.
When running at high idle we cracked the injectors on at a time and the first and third cylinder significantly slowed the revs but the centre one didn't.
A smaller effect than the others.
says this would explain why the vibration only shows up under load.
2 foot seas or more, head wind
and three quarters revs.
He is suggesting either re build this engine or replace.
Ow. That hurts financially.
I am surprised as I thought the engine is low in hours and as its maintained in a charter
fleet it has been well maintained.
I thought that diesel
engines ran for ever if well looked after.
He has checked the shaft alignment and the transmission plate connection.
I have not been able to get it to vibrate at the dock
or just outside in the bay to show the mechanic.
I am taking the boat out for a few days and the mechanic told me to crack the injectors one at a time as we did at the dock
if the vibration occurs again under load.
I will try that.
I have asked the mechanic to do a compression
test to prove the centre cylinder is weak.
He says this is time consuming.
Is it worth it?
If his analysis is correct whats the best solution here.
Re build or replace the engine?