R21 Yanmar 30 rpm

[Ron B]

We have put about 50 hours on our recently acquired Martini R21 and have some conclusions and more questions.
We boat in a SE Florida canal system which is no wake to begin with. We have learned that we reach hull speed, 5mph, at15/ 1600 rpm and max cruising at about 2100[with too much wake]. The engine will top out at 3600, but wow what a wake!
In any event we love the quiet and smoothness at 1600.The economy is less than a quart an hour also!
I keep hearing a diesel must run at 80%of rated which is about 2800, which would get us arrested before we got out of our canal!
The question. Will the 3YM30 tolerate running at 1600 for an extended time? The engine has less than 300 hours. I understand a buildup of carbon can be expected in the exhaust elbow, but this is a minor problem.
Any advice would be appreciated Ron B Lighthouse Point Fl

 

[Robert H. Wilkinson]

Ron, diesels don't like to run with "no load". The hp they are required to produce(percentage of load) is more important than the rpm. Yanmar often uses the same block for many different applications and dials in the hp .

In a stationary application such as a generator they are often set to run at a constant rpm.

Modern turbo diesels are capable of higher rpms for use in propulsion applications(cars, trucks, boats, etc.) The main thing is not to idle them with no load for long periods of time.

In your boat - whenever the drive is engaged the prop puts a load on the engine. I would not be concerned about running it at any particular rpm.

The Yanmar is a top shelf diesel and you have a great boat - enjoy.

Regards, Rob

edit - On rereading your post, I believe I have the same 3 cyl. Yanmar on my generator . It runs at 1800rpm every day for 4 hours. Has over 12,000hrs. on it now.