Cruising RPM?

[Inlet Marine Services]

As a Yanmar dealer I am asked this question all the time. Yanmar posts a cont duty rpm but thats not always what you want to run. Yes cont duty is 80% of full rpm and you can run there all day long but is that how fast you want to you? Many of my customer cruise at 2200 or 2500 but with only one warning, you need to run up the rpm to 3000 and run for 10 to 15 minute so carbon does not build up in the exhaust.

[GordMay]

Originally Posted by Inlet Marine Services

...Many of my customer cruise at 2200 or 2500 but with only one warning, you need to run up the rpm to 3000 and run for 10 to 15 minute so carbon does not build up in the exhaust.

Would it be fair to say that you want to run it up to (& keep it at) operating temperature?

[JiffyLube]

Originally Posted by Jack Long

Ketch, sorry I was snarky.

Don't feel bad, he has a tendency to make people feel that way....lol

[Jack Long]

I will give more details later but I thought I would share a brief update on this... I will confine this post to RPMs and maybe some teasers.

Cruised most of the way at around 2,500 RPMs.

There appears to be "something wonky" with some of my controls. Uh, so, I have a key that can be in two positions, a start button, a kill knob, a blower knob, and another knob that I thought was a choke but the P.O. thought was a second blower (and told me diesels don't use chokes). I don't think it is another blower but for some reason when I pull it the tach READS about 1,100 RPMS lower than when it is in. The motor stays the same.

Sadly, when I left I had this pulled out... so I think I ran the motor a lot harder than I meant to for the first couple hours.

Actually, correction, I ran the motor about right for about an hour- tach READING 1,500 or so... Once I was comfy I decided to put the throttle up and see how things went. I ran it up to a little over 2k, which was probably a bit over 3k. I did this for a while and then thought, well, I am going FAST but lets see what 3k feels like... And discovered I had no more throttle to give it.

This freaked me out so I eased off and ran at what the motor seemed to sound best at. Which, once more, READ about 1,500. Later I realized the tach issue and spent the rest of the day between 2,300 and 2,600.

She ran great, I think I used about a gallon an hour or so of fuel. Although the fuel gauge read 100% full- including after I ran out of gas. It was 4:30 when this happened and adding diesel (as you guys know I am sure) didn't get it running. I called information with my cell and there were no listing for "yanmar" anything. I called West Marine in Alameda and asked if they could refer me to a Yanmar service place. They did and I managed to get ahold of a manager at a shop right before he left. He gave me his personal cell number and helped me out while I got everything running.

I am going to make some VERY [expletive deleted] POSITIVE reviews about this guy and his shop. But I want to have slept first. But this guy put in about 1.5 hours of his personal time and cell minutes to help me. For no reason other than he was awesome. So, like, forgive me when I commercialize him a bit in the hopes that good karma comes back to him.

Oh, the fastest speed I saw was close to 8 knots but I didn't have the meter running when I was blasting along at full throttle. Depending on where I was with the tides I got as low as 3.8 and as high as 7.2.

Anyway, tons more mail to process... I made such good time I did it all today but because of the running out of fuel problem missed my window to get into the new marina and ran aground... Anyway, babbling now. Sorry.

Luck,
Jack

[Northeaster]

Related question - If a boat has been (and still is!) overpropped for years, and therefore has never been run past approx 2000rpm (yanmar 2gm), will it hurt now to slowly try to bring it up to max rpms in neutral?

I cannot bring it anywhere near max rpms while in gear, as white smoke will come out, and I don't want to overwork the engine to the point of causing damage!

Explanation - just installed a new magnetic pickup tach, as the boat never had one, and i wanted to know my rpms. The specs say 97 teeth on my engine. The teleflex guage is set for range 90-110 teeth - it may need calibration, but I think is somewhere in the ballpark, as idle shows about 800rpm.
I can rev to about 3000 in neutral - may go more, but I didn't want to damage it!
Will put out white smoke above 2200 rpms (again guage may be off some).
On my 30' med displacment sailboat, I can do 5 - 5 1/2 kts around 2000, but will smoke it I try to go above 5 1/2 or 6 kts.

PS the engine works / sounds very good until it revs to the point of white smoke - does not overheat, etc!

I thought it was overpropped anyway as it has a 15" x10 3 blade prop - the prop caclulator showed I should have something like a 15" x 7.4 or a 14" x 8.6.

I will likely have some pitch taken off, once the boat is hauled in the fall, but want to know that it will not damage it more as is.

[Northeaster]

NOTE- I decided to start a new thread, so I didn't take away from this one. Please ignore the last post!