Good day. all of our bottom trawler fishing vessels bar one use different makes of 4 stroke medium speed marine engines. however we have one vessel that uses a 2 stroke wichmann engine that gives us continual problems and premature failures… most recently a main bearing failure after 22 000 hours, OEM recommended replacement interval 35 000 hours. my question is: what is it about a 2 stroke engine in this application that makes it far less common than a 4 stroke engine? I am seriously looking at re-engining the vessel and am looking for a suitable 2200kw medium speed engine - preferably reconditioned. any views would be appreciated.
Are you running consistant speeds on your engines? Two-stroke engines like steady speeds on the high side of their power band. If you are doing a lot of maneuvering or other things that require reduced engine speeds, it often results in incomplete combustion leaving raw fuel in the cylinder after the power stroke. On the subsequent compression stroke, that raw fuel can detonate prior to timed injection. This is called ‘detonation’ and is a well documented cause of premature bearing failure. One way to check for this is to examine the crowns and skirts of your pistons (while you are replacing your errant bearing). If you see pitting on the crown or scuffing on the skirt of the pistons then you have been experiencing detonation.
Hope this helps.
haven’t Wichmann diesels been used in trawlers successfully for decades?
Not so much now but plenty of east coast “draggers” had detroits, lot of the smaller ones still do. Often a 92-series Detroit…ccaptain loves their sweet melody.
They like being under a good load at higher Rpms, like previously said.
[QUOTE=c.captain;121327]haven’t Wichmann diesels been used in trawlers successfully for decades?[/QUOTE]
Wichmann engines were great until the government subsidy ran out. Kinda like obamacare!lol!!
Wichmann engines were outstanding. I worked with the 4 and 5 cyl models in the early '80s. Medium speed @ 375 with intergraded CP system. Spares were getting hard to get when they crashed in the '80s. I’m sure they were picked up by one of the conglomerates…
[QUOTE=txwooley;121325]Are you running consistant speeds on your engines? Two-stroke engines like steady speeds on the high side of their power band. If you are doing a lot of maneuvering or other things that require reduced engine speeds, it often results in incomplete combustion leaving raw fuel in the cylinder after the power stroke. On the subsequent compression stroke, that raw fuel can detonate prior to timed injection. This is called ‘detonation’ and is a well documented cause of premature bearing failure. One way to check for this is to examine the crowns and skirts of your pistons (while you are replacing your errant bearing). If you see pitting on the crown or scuffing on the skirt of the pistons then you have been experiencing detonation.
Hope this helps.[/QUOTE]
thanks for this txwooley. it is consistent with our enquiries with some engine manufacturers. we are seriously looking a replacement 4 stroke engine in late 2014.
2200kw, EMD is likely your cheapest solution for a medium speed engine. A 16 cylinder roots blown 645 would be your ticket. A turbo 12-cyl 645 is right close to 2200kw. I think the current 8-cylinder 710 series engines are also around 2200kw. They are big for their horsepower, though. Might be a tight fit in your engine room. If you operate in the US, there is a lot of support to bring older EMD engines into current emissions compliance. It’s still a 2-stroke, though. High speed engines are getting very reliable Cat 3500 and Cummins whatever. A 16-cyl Cat 3500 can run 2200kw all day long and runs a hair over $500k new which is very cheap for that horsepower. Supporting systems are also cheaper for high speed engines (pumps, coolers, reduction gears). Midlife overhauls are murder, though (about 100k and 5-6 days of downtime).