I'm thinking of repowering my '75 28 fbc with Cummins 6bta's. Thinking low rpm= economy cruise, high rpm="Holy S&!#"!!!!! top end. Measured my neighbors 31 with the cummins, and it appears they will fit, except for height. will necessitate re-configuring engine hatch area, and it would add about 800 lbs over Yanmar 4 bangers.
Am I nuts?? Has anyone on this BB ever seen this done? Cap't Pat?? Bruce??
All comments/thoughts/ideas welcome.
Irrepressible Hot Rod Gene
Moderators: CaptPatrick, mike ohlstein, Bruce
Irrepressible Hot Rod Gene
""Procrastinate now!"
Ted,
Your quote about having it and not needing it is very appropriate for Gas, but not for diesel.
It is good to have "reserve power" with a gas set up, but you really want to try to size your diesels to the speed and conditions you will run the engines at 85-90% of the time or you really are not gaining anything. At all. In fact it just isn't great for the engines.
Pick your desired cruising speed and buy the appropriate engines. If you want a speed demon boat, don't think of a B28 or 31 as your first choice...
Dug
Your quote about having it and not needing it is very appropriate for Gas, but not for diesel.
It is good to have "reserve power" with a gas set up, but you really want to try to size your diesels to the speed and conditions you will run the engines at 85-90% of the time or you really are not gaining anything. At all. In fact it just isn't great for the engines.
Pick your desired cruising speed and buy the appropriate engines. If you want a speed demon boat, don't think of a B28 or 31 as your first choice...
Dug
Having done many repowers and then having to service them afterwards I will leave you with the following:
Ten pounds of crap in a 5 pound bag.
Your gear ratio will need to be along the lines of 1.25:1 to fit the props.
At that ratio you are losing engine efficency.
Your better off with a higher rpm diesel in that application.
One of Carl's new projects at Elite is putting the 315hp Yanmar in the 28.
He's done 3 or 4 now. When I asked him about fit, he smiled and said its tight.
John Holmes tight or Pee Wee Herman tight?
Johnny tight.
Not a good thing for the service side.
Not a practical application for the 28 in my opinion.
Ten pounds of crap in a 5 pound bag.
Your gear ratio will need to be along the lines of 1.25:1 to fit the props.
At that ratio you are losing engine efficency.
Your better off with a higher rpm diesel in that application.
One of Carl's new projects at Elite is putting the 315hp Yanmar in the 28.
He's done 3 or 4 now. When I asked him about fit, he smiled and said its tight.
John Holmes tight or Pee Wee Herman tight?
Johnny tight.
Not a good thing for the service side.
Not a practical application for the 28 in my opinion.
-
In Memory Walter K
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Every time I read about some of these "overpowerings" I wonder if they realize that with the proper prop for their high hp engines, there will be a big bite taken out of the water on the low rpm end of the scale. Even if you don't care about slow trolling for bass etc., you still want to move sloooowly in your marina and while getting into and out of slips. Most of the 6bta's start to rumble at anything below 7-800 rpm. Put both engines into gear and you'll rocket out of your slip. If you want to go real slow, high rpm diesels or trolling valves on your transmissions are the way to go, otherwise learn to troll on one engine and pop it in and out of gear when in your marina. Walter
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