Originally Posted by smurphny
I was conveying what the power curves show from the Manual. The 3GM30F was advertised at 29 hp, I believe, but that must be at maximum revs. Assuming the data is correct in the Yanmar manual, when I cruise at 26-2800 rpm. the engine is producing around 15-17 hp at the flywheel and even less at the shaft. At 3000 the engine feels like it's revving too high and I'm pushing it too hard. I reach my hull speed of around 6.5 knots at around 2600 rpm. Pushing it any higher just results in diminishing returns.
Maneuvering an A35 in close quarters is difficult. In reverse you have virtually NO control until you gain enough speed for the rudder to grab some water. Keel attached rudders have much less effect than rudders farther aft. I always approach any dock on my port side so that the prop wash in reverse will kick the stern in even if I have to wait to get in. Slowing forward momentum takes a Loooooong time. Everything needs to be planned and done in slow motion. I would also suggest putting a midship cleat in to use as a spring line attachment. The A35 has no midship cleat. Jon Eisberg gave me a great idea for installing cleats (which I did) a few months back so look up old posts from last summer for the details.
Yep...that does it. The Beta 20hp ain't going to work! Thanks for all your input, and the love you've shown your Alberg!
BTW, I had a friend who had the same 2GM20 I do (before I did). He hated it! Thought it was underpowered, had mechanical problems, etc. A mechanic at a leading Yanmar dealership asked him what he cruised at. He responded 2500 RPM. The Mechanic said: "That won't do it. This motor wants to work. Bring her up to 3000 and keep her there." (you won't find that anywhere in my Yanmar manual)! He increased the RPM, and fell in love with the motor, after hating it for 5 years!
I've found that some people who have been around diesels for years (unlike me) have a hard time thinking of a diesel cranking that fast. My motor is twenty years old and didn't receive the best care from PO's. Yet, it has been almost trouble free (two minor exceptions) for the 6 years I've owned it, and scoots my 4.5 Ton vessel along like a champ!
I assume from your comment about "living with a Yanmar" you may feel like he did, about your motor. Don't know, but maybe a prop conflict with your 3GM? Might be worth talking to a good Yanmar guy.