Tag: 3C Yacht Services

I just finished another pre-purchase mechanical survey, and doing a blow-by test on the engines is part of our investigation. Each time, people always ask ‘What is blow-by?’

Basically ‘blow-by’ is the air and combustion gases from the cylinder, on top of the piston that escape past the piston rings into the crankcase. No engine will have perfect sealing rings, though as the rings, and cylinder wear the blow-by will increase giving an indication to the engine health.

Blow-by not only is a tell-tail on the engine health, but there are several negative effects. Blow-by not only pressurizes the crankcase but also introduces combustion gases that contain unburned fuel, particulate matter, and oxides of nitrogen emissions. They also create condensation due to the temperature differential of combustion gases and the crankcase.

Blow-by tears the oil from the piston and rings. At first it vaporizes and then it becomes an aerosol, which you see as a film or fumes around the crankcase vent tube. When mixed with engine oil, blow-by produces sludge and acids that attack all engine parts. The unburned fuel dilutes the lubricity and viscosity of the engine oil, attacking engine bearings, the valve train, and cylinder walls.

When the blow-by becomes more than the crankcase ventilation can handle, other problems start to happen, from blown out crankshaft main seals, to an engine ‘run away’, where the oil vapor becomes a fuel for the diesel engine and it then starts running on it’s own engine ‘oil fuel’, with no ‘standard way’ to shut it down – a run away engine is rare, but extremely dangerous.

Power Point presentation from the Mining Diesel Emissions Conference October 7-9th, 2014 – Retrofit Crankcase Ventilation for Diesel Engines: https://mdec.ca/2014/S6P2-Stekar.pdf

Controlling Blowby in Diesel Engines by Ray Bohacz, 3/20/2019 Successful Farming: https://www.agriculture.com/machinery/repair-maintenance/controlling-blowby-in-diesel-engines

Causes of Diesel Engine Oil Blow By by Tony Oldhand – It Still Runs https://itstillruns.com/causes-diesel-engine-oil-blow-6930901.html

Who else has seen this?

Raw water pump impellers – an item that should be on a regular service check list, but not always done. Some boat / engine combinations do not even allow access to these critical items to keep those expensive engines cooled. It’s a problem seen far to often, where the impellers break apart, then scatter little pieces of itself through the raw water cooling circuit, which then has to be pulled apart, inspected, and cleaned of debris, to ensure no plugged passages.

It’s a time consuming, high maintenance item, that can lead to some very expensive repairs! Ask us how Baudouin has addressed this issue, saving you money and down time! info@3cYachts.com

Twin Cummins 6BTA5.9’s lifted out for rebuilding after the interior, galley, and seating was removed to gain access.

Staging – removal of the engine from the ‘hole’, where the ‘hole’ was shorter and narrower than the engine! Some items removed from the engine, and with some very careful lifting with our specialized Gantry for jobs like this, one engine was staged to the center to the door, and readied for the crane to make that final lift out through the door, as seen behind the engine.

Crane arrived, setup, and then attached to the staged engine, and ‘threaded the needle‘ through the doorway without any damage, or issue.

After the 1st engine was out, then the 2nd engine was lifted out of it’s hole with the Gantry, and moved over to the center of the doorway again – staging it for the crane and lift out.

A lot of thought, and planning went into this to ensure a smooth process, without any issues or collateral damage. A thank you goes out to Vic City Crane, as a good crane operator is imperative to this project. A thank you to Anderson Precision Engines, as they will be ensuring a professional rebuild at their machine shop.

Twin Cummins 6BTA5.9’s getting ready to be lifted out for rebuilding after the interior, galley, and seating was removed to gain access.

Staging – removal of the engine from the ‘hole’, where the ‘hole’ was shorter and narrower than the engine! Some items removed from the engine, and with some very careful lifting with our specialized Gantry for jobs like this, one engine is now staged, and ready for the crane to make that final lift out through the door, as seen behind the engine – stay tuned!!