Shakey Perkins Diesel

[Marc Robic]

(I have a Perkins 18HP, 3 cylinder) Sometimes, at idle, the engine will shack a lot. But I give it a quick shot of throttle and it settles down nicely. It is not a daily occurrence, but enough to drive me nuts.... (the engine mounts are new, engine is aligned) And it only happens in idle. Wonder what fellow Catalina and/or Perkins Diesel owners think this might be. Since increasing idle fixes the problem, can it be water in the fuel?

 

[Bill Roosa]

it is a 4 cycle engine with 3 cylinders!!!! It is NEVER going to be very smooth at any speed. I've never understood why anybody would make an 18 HP engine with three cylinders. Much better to just make it 2 and make each cylinder bigger. Fewer parts, smaller overall engine length, lighter........just plain dumb design.
One thing that makes it even worse is mismatched cylinders due to carbon build up in the cylinder/piston head. three cylinders seem to be very sensitive to this which is why a throttle blip can solve the problem. Recommend "running the snot out a it" all the time. Use max cruse speed as much as possible.

 

[Marc Robic]

Dear Bill, I appreciate your taking time to respond but with all due respect, this is and has been an awesome engine and has always been a great and relatively quiet diesel engine. I don`t where you get your information, or perhaps it`s just an opinion about 3 cylinder diesel engines, but I can assure you`re mistaken. FYI, she`s 21 years old, still looks brand new and has never cost be anything other than regular simple maintenance. (oil and filters. Changed engine mounts 2 years ago)

By the way, two days ago, I purged the water out of my filter and she`s back to her great running self.

 

[Jim 5757]

We're very happy with our M3-20 Universal - also 3 cylinders! No problem with vibration.
Isn't this engine related to or a decendent of the Perkins?
Glad you found the simple fix!

 

[All U Get]

Maybe the idle is too slow. Our yard mechanic check ours last season and set it at 800rpm. The Perkins runs smoother now. Good point about giving it a hard run, I do it with ours.

All U Get

 

[Bill Roosa]

Hey Marc
no doubt about the quality of the engine. All I'm trying to say is 3 does not divide by 4 evenly so you either design that engine so it is dynamically balanced and the power strokes are uneven or you design it so the power strokes are even and it is dynamically unbalanced. the latter being more typical. 4 stroke engines with 1, 2, 4, 8, 12... cylinders don't have that problem.

 

[dziedzicmj]

It is NEVER going to be very smooth at any speed.

The three cylinder runs much more smoothly than a comparable 2-cylinder (e.g. Westerbecke).

 

[dziedzicmj]

My first guess would be to look at the fuel filter(s). It seems like you are getting some restriction in the flow?? If purging water from the primary filter helped, this would explain why it was shaking.

 

[Skipper]

The three cylinder runs much more smoothly than a comparable 2-cylinder (e.g. Westerbecke).

Not that much.
My dock mate years ago had a Catalina 270 with a 3 cyl Perkins 18. I remember him having minor complaints but it was a smooth runner. I was with you and thought a 2 cyl would be less smooth, but I've had an M18 Universal for the last 5 years and it's a sewing machine. Get some slight vibration, more of a tone really, at low RPM but it's soothing.

 

[dave_and_dd]

a 3 cylinder should be smoother than a 2 cylinder (at least a bit). it's not about 3 dividing into 4, it's about dividing 3 into 360...which it does....

Dave

 

[Calif. Ted]

I'm Skipper's dockmate from years ago, that engine will shake like the boat's coming apart at too low an idle speed (about 800 rpm), just had to adjust the idle stop up a little on mine. They are cold blooded to start, needs some throttle when cold, but a pretty smooth little engine. You could almost use the temperature gauge as a tach, it wouldn't get to full temp until you went to full speed.