Prop or injection pump or?

[Burton]

We finally got this boat in the water. It is a 25 “Deluxe” FC. We bought it very cheaply, and know almost nothing of its history. It has a Yanmar 40 hp that supposedly has only 98 hours on it according to the engine meter. It does look fairly new, other than having sat for years, some minor rust in spots. It is a 3JH3E, and I just had the injectors cleaned and tested.

The boat will only do 9.5 kn at WOT and maximum underway RPM reached is 2850. However, not under load, the engine easily runs up to 3600 RPMs which is its rated max. There is no black smoke to perhaps indicate the motor is laboring heavily while underway. The speed calc is by GPS, but also an average estimation, because we were going two directions on the river with the tide running, too. From what I’ve read it ought to do a bit better at WOT, like 12 kts.

Is this most likely a case of an over-pitched prop? Or an injection pump too lean? The boat is moored, and I did not measure the prop before launching...oops. The shaft looks new, the prop looked old.

Will we damage the engine if we run this way for a time?

Any advice is much appreciated!

[dkirsop]

Get the dimensional data from your prop, it will be stamped on the hub. Then contact a Yanmar dealer or rep and get them to determine if it is correctly matched to the engine. They will also need to know what reduction gearing you have on your engine. What you describe sounds to be either an oversized or over pitched prop.

[Mainer]

Wow, I was surprised to read of your concern re WOT speed of "only" 9.5 knots, and hoping for 12 knots. The folks I know with A25's seem to cruise happily at 6 to 7 knots. I'm not knowledgeable of the difference with the "Deluxe", but would suggest your speed expectations may be a bit high for your boat, even if you do find the boat over propped.

As most of us have found, anything much over "hull" speed is just pushing extra water and gobbling more fuel. Such is the case with virtually all displacement (non planing) hull boats.

I'm happy cruising at 8 knots at 1750 rpm's in my A27, though I have a much larger Isuzu 157 hp engine.

Separately, you're sure in a nice boating/cruising area of the Maine coast. We plan to be up there in a few weeks cruising from Portland area.

Dick

[Burton]

Thank you, all.

I’m going to borrow an underwater endoscope camera and see if I can get the numbers off of the prop. If not, into the water I go....

As to speed, my concern was not to go faster than 9.5 knots, but that with past outboards I have understood that maximum engine RPM at wide open throttle should be attainable. And that if it will not do this, or typical hull speed not reached, there is a problem of the prop being mismatched to the engine. I recall reading of others that were getting 12 knots out of their 25s at wide open throttle. Perhaps I recall wrongly.

I’ve got a very similar three cylinder Yanmar in my tractor. In the manual they warn against long periods of low rpm, and say that it is designed to run fine at higher RPMs.

Hence my concern at not being able to get up to its rated RPM underway. Perhaps this performance is normal— this is my first boat like this.

[Dieselram94]

Hmm, my thoughts are you are over propped. Any smoke at any rpm? Starts easily? Runs smooth? Any sign of diesel in the oil?
My guess is it’s just over propped. I’ve seen my boat at wide open do almost 11 knots, and that’s with a Perkins 4.108 50hp...but it was I believe over 3000 rpm.
Also, hello from mid coast maine!

[dkirsop]

Yes, the prop needs to be matched to the engine if maximum fuel economy is to be achieved as well as to avoid long term damage from lugging the engine. Once matched the engine should just be able to attain full rpm at maximum throttle.

[Burton]

It starts almost instantly. No smoke. Purrs like a kitten. It did not occur to me until now, but the guy who serviced the injectors said they were very dirty. He ran them through their ultrasonic cleaner three times, 45 minutes each time. I would think the smoke would be curling out, but it isn’t. However, this may indicate but the engine is not running lean, but was lugging... (?)

We are tied up at the float dock in Ellsworth—it is a great little harbor, but the water is real thin on the way out at low tide— We’ve seen it down to 1.1 feet, and that is accurate. One must stay on attention with the buoys, and watch for tidal drift, as it will take you out of the channel though you are steering straight at the next buoy...and getting out of the channel can put you on the rocks fast. (My son recently towed in a guy who destroyed his outdrive there—the guy was swinging wide of the buoys. He blamed it on the harbor!) There is an Albin 27 here that is beautiful! I’ve got some years of work to get this 25 looking good.

[DesertAlbin736]

One must stay on attention with the buoys, and watch for tidal drift, as it will take you out of the channel though you are steering straight at the next buoy...and getting out of the channel can put you on the rocks fast.

That's why having a good chartplotter/depthsouder with up to date charts helps. Instantly see where you're at & headed at all times. Especially important in treacherous waters as you describe. One of the good things about an Albin 25 is you can have a chartplotter right in front of you & a chart table to lay out paper charts too. I'm partial to Garmins, but other brands are fine. This 741xs is not the latest model, but the touch screen is nice. The purple line is course to a temporary waypoint which you can pick by just touching the screen. While the waypoint is active you get not only lat/long position, speed, depth, and heading but also across the top you get bearing & distance to waypoint, ETA, & left or right distance off the rhumb line. This was in the San Juans of Washington State, with Patos & Sucia Islands off to the right, Saturna Island, BC off to the left & the US-Canadian boundary line down the middle. Depending where you are in these parts & what stage the ebb or flood tide is, you can get some wicked tide rips & currents moving faster than your boat speed.

20180625_111841.jpg

I add Kleen Diesel (TM) additive at each fuel up.

[Ambler27FC]

Sounds like a significant over-prop. I believe the thumb-rule is to reduce 1 degree of pitch for every 200 RPM, which can be done at a reasonable cost. I believe you want to be within a certain percentage of rated RPM to avoid long term issues (engine specific). Ideally you are not operating at WOT for any length of time - very fuel inefficient. Low RPM is also an issue for engines - most significant for sailboats running the engine to recharge batteries.

[honza]

I agree, but why it is not an issue for truckers running their engines idling every night, the whole night at a truck stop? Their engines do not seem to mind.

[Dieselram94]

I agree, but why it is not an issue for truckers running their engines idling every night, the whole night at a truck stop? Their engines do not seem to mind.

Idling a diesel, is not good for long periods of time. It results in cold combustion chambers and incomplete fuel burn, some unburned fuel goes by the rings hastening wear. Always best to give them a bit of throttle (about 1200 rpm) if your going to let it idle for a long period. This brings the combustion temp up.

[honza]

Beta says 1800 RPM. Calder something similar. None of them trucks idles that high. Maybe, it burns out, if you give it 16 hours of full throttle after 8 hours of idle?

[Ambler27FC]

That is a real interesting point about trucks running all night. I wonder if they are working off the heat developed during the day. Beta recommended 1200 RPM minimum for long-term running of my engine - and the engine does barely heat up below 1200 RPM.

[Dieselram94]

That is a real interesting point about trucks running all night. I wonder if they are working off the heat developed during the day. Beta recommended 1200 RPM minimum for long-term running of my engine - and the engine does barely heat up below 1200 RPM.

No, the heat developed from running down the road is quickly dissipated if idling. In fact best thing to do for a overheated diesel is to let it idle to cool it down. Basically the engine becomes a air pump and the cooler air cools it.

[hetek]

Dont rule out a clean bottom and a reasonable cargo load. Dont bring the entire contents of your garage and kitchen on board. Both will rob you of speed.

I would suspect the prop also.

With so little time on the clock, it suggest a fairly recent repower. Im told that to validate warrantee, Yanmar requires a technician to sign off on the job - not just rigging but also performance. That's saying it was a new Yanmar at the time (not a rebuild).