R25 engine choices

[oldgrowth]

[Doryman]

[thataway]

If the boat was heavily loaded or punching into wind and seas, and the engine could not reach WOT as per specs, that would lug the engine. Many boats are intentionally over proped for "better fuel economy"--which means that they will not reach WOT.--each time you run the engine up to try and get to WOT, it could be lugging the engine if it is proped incorrectly and wil not reach full RPM. Althugh this probably does not apply to the Ranger or C Dory boats, I have seen a large number of boats sent from the factory with the wrong prop. We were cruising along side a very similar boat, which could ony go 5 knots max--we could go over 8. I loaned him my spare prop--and he immediately got the same speed we did! In these cases, I have to assume employee error, or they just didn't have the correct prop--again not applicable here, but it can happen, so something to watch for?

A semi displacement boat is farily easy to lug the engine on. If the engine is correctly proped this would not happen on the R 25. I consider the R 25 a planng boat, since the surfaces aft are flat, and with enough hp it will get on a true plane. The best way to measure if an engine is being lugged is to put a pyrometer in the exhaust. How many of the R 25's have pyrometer? I would have one if I was running a Ranger 25 at more than displacement speeds (over 8 knots) The pryometer measures the exhaust temp. If the exhaust temp goes up this is an indication of lugging the engine.

If the boat stays at displacement speed with the 110 hp engine, it would not lug. But many displacement boats lug their engines. We were bringing a 45 foot racing sailboat I owned back from the La Paz Race punching against the wind and seas, we found we could not operate the engine over 1800 RPM (Red line of 2600) because the exhaust temp rapdily rose. In calm water this was not a problem.

Many of us have pyrometers in our diesel trucks; there is is farily easy to know when the engine starts to lug--the speed decreases with a constant accellorator or Cruise Controol. Easy in the truck to down shift--no down shifting in the boat.

[Old Dog]

A question that I'm sure Thataway can answer and thanks if you do plus a comment.

Clearly warmed up and loaded is the best way to run diesel engines. I've gotten conflicting opinions, however, on how to warm up a diesel engine. Most say to let it sit at idle until it reaches some temperature (varies). Others say, it takes too long to warm up at idle, put a load on the engine just not a very high RPM. With our most recent previous diesel it wasn't an issue since the boat had a hot water heating system and we almost always had that on prior to starting the main engine so it was always warmed up and ready to go. The R-25 in the cool PNW waters seems to take longer to warm up at idle than I'm comfortable with so we've been getting underway at idle even though the engine is not as warmed up as I'd like. Leaving it at very low rpm until it does hit normal operating temp. Not sure about this so that's my question. Advise on getting the engine to operating temp?

Out of curiosity, I ran Thataway's comment about one gallon per hour per 20 horsepower against the Yanmar 110 charts and also some personal data that I had. These general rules are great and this one like a lot of others seems to work. The real reason was that I was trying to confirm my earlier observations on fuel usage so as to get a better idea what the practical range of the R-25 might be.

Using either the general rule or the Yanmar charts (see TimOb's original post if you don't want to read the charts), the 110 Yanmar burns about 2.5 gallons per hour at 2400 RPM, about 3 at 2600, and about 3.9 at 2800. Based on my admittedly very limited experience to date, those RPM's yield between 6.5 and 9 knots.

The math on this is interesting. If the numbers were perfect and the world was perfect, and if you wanted to use no more than 50 gallons of your perfectly full 75 gallon tank, the answer would be:

RPM Speed Fuel Use Hours Distance

2400 6.5 2.5/hr 20 130 nm (note - edited from km - which was wrong)

2600 8.0 3.0/hr 16.7 134 nm

2800 9.0 3.9/hr 12.8 115 nm

The world isn't perfect, the numbers are approximations, only the math is precise so based on all this imperfection, I will, until proven wrong, assume a conservative, practical 125 nm range for the R-25 which is long enough to go just about any where in PNW including as Mac on Island Ranger just demonstated to the Alaskan waters.

One problem with this short range and the frequent fuel stops that it means every time you fill up on the water, you risk losing the fuel cap - a very poor design for on the water use. Has anyone found a better fuel cap?

[Hunkydory]

[thataway]

Of course if you want to really have the "best", pre oiling is an excellent idea. This is a pressure pump which is turned on before the engine is started and fills the oil galleries so that there is oil at every point as the engine fires its first stroke. I have always started the engine, let it run until oil pressure was up in the engine and transmissions (some of my larger boats have had oil pressure guages on the transmissions) and then put the boat in gear. Certainly in the RV world it is generally accepted that prolonged idling is not good for the engine (or your neighbors)--most 0n the road trucks have a "high idle" setting--as do some RV's. Realistically I would start the enginies, cast off the lines and go at an idle. It usually takes a minute or two to cast off the lines in a larger boat. But I would never start engines 10 or 20 minutes before shoving off.

I would be a little surprised that the range at 8 knots would be more than the range at 6.5 knots. Lets assume that the LWL of the C Ranger is 22 feet: With a sq root of this being about 4.7, 6.5knots is slightly over l.34 x sq rt LWL. This is an accepted magic number--beyond which a boat has to start climbing over its own bow wave (some minor variations according to the lenth to beam ratio, weight and hull form)--but it is a very good number. If you don't already own "The Nature of Boats, by David Gerr, it is a very good book to have in the library--so is "V oyaging under Power" by Bebee and Leishman. I have the first edition for fun, as well as the most recent edition, since I have had some experience with "Passagemaker", Bebee's boat.

At 8 knots you are at 1.7 x sq root LWL, and that is not as effecient as slower speeds. 9 knots will be less effecient yet. The less effeciency should mean less miles a gallon. For the Ranger 25, I would expect the best effeciency would be in the 5 knot range, but that is going to be too slow for most folks. It may be necessary to get long distance cruising.

I thought that someone had done detailed sea trials with fuel consumption, but I could not find that, which is surprising. I probably just missed it.

The "small" fuel tank is certainly a good question. If you are getting 5 miles a gallon (a gallon an hour at 5 knots) then you would expect a realistic range of slightly over 300 miles. That would make most of the PNW available. I figure at least 200 mile range to do Alaska in any boat.

[Old Dog]

LET ME START OFF WITH A BIG APOLOGY. I must have had my head screwed on backwards as I wrote the last message because I did not mean to use km (kilometers) when I meant nm (nautical miles) Since I read speed in knots, I think in terms of nautical miles and simply mislabeled them. Sorry if that confused anyone as it woud have me. Obviously - I screwed up big time. I will go back and edit the previous message to hopefully keep others from getting bad info.

However, as noted, the math is precise - the data less so. Even if read correctly off the charts, the curves have been fit to the data so any intrepretation of the charts will have an error factor.

Actually, it's all beside the point. Within a reasonable range for cruising speeds, the data would suggest something around 125 nm as a very conservative cruising range plus or minus whatever factor to be more precise or less conservative or more conservative or whatever one might wish to apply.

Some might think using only 2 thirds of the tank (50 gallons) as a basis is too little - others might like more of a reserve. Matter of choice and the local conditions - in this case the availability of fuel. Frankly, it's obvious that the best cruising range is at idle but who wants to do that.

Anyway, I will be interested in seeing some hard data when someone can produce better info based on actual use of the boat. Meanwhile, I will plan legs of no longer than 125 nm and recognize that there may be conditions where that is too long or where that is not a problem.

Oh - and thanks Thataway for your comments on warming up a diesel. Pre-oiling is out of the question as is pre-warming but I agree with you that letting the engine idle is not the answer despite the advice you see fairly regularly on letting the engine warm up. Glad to have some confirmation on that.

[thataway]

Old dog, I suspect we all understood that you meant Nautical miles--not a problem. The pre-lube pumps are not all that expensive. Is it worth the cost? It is arguable. If you run the engine regularly, there will be more oil in the galleries than if you let the engine sit for a week. This is probably one of the reasons that commercial engines last so much longer than recreational engines do.

You are correct that real time usage is the most important. If you look at the "Boat Test.com" tests on the C Dories, their numbers are significantly better than real conditions. The usual reason is that the boats are light, (small amounts of fuel, water, gear and people) they are new, with no bottom paint and clean bottoms, as well as in calm conditions. For example the TC 255 gets 2.78 nautical miles a gallon at 17 knots. with a range of over 400 miles. In reality most of us are getting 2 to 2.4 nautical miles a gallon.

One of the factors not taken into account in the engine curves, is the prop slip. There will be more slip at the higher speeds, as well as more power (and fuel used) per each incrimental increase in speed. In my experience in some boats--an increase in boat speed of one knot is equal to doubling the fuel consumption!

[TimOb]

Ok, so refraining from running the engine at a constant lower RPM range by periodically increasing the throttle per Bob's suggestion is really to manage carbon deposits. Correct?

Has anyone thought about additional fuel capacity? I know Mac brought along an extra 5 gal bottle on his Alaska trip. But what about something more permanent? Is there any room? If so, where?

Tim

[oldgrowth]

[thataway]

You can do what Dave suggests, if your engine has a selenoid fuel shut off. I did this occasionally with my Cat's--hit the stop buttom and the start at the same time. Not sure how much oil pressure one gets with this--but it will get some oil up into the galleries if the engine has not been run for some time--and you have plenty of starting batteries.

For whatever reason this has not been real popular in the boat crowd--and it may well be fear that you can run down the batteries when starting the mains.

[captd]

Dave,
Yup, The Yanmar mechanic told me to do it when needed so it must not hurt a thing.
Captd

[dtol]

I still think they should have put the Volvo D3 160 horse in the R25. I probably would have one now if they did.

[dtol]

I have a question about fuel management relating to issues about storage, condensation, bacteria problems, etc.

Is it better to have one large tank or would a confuguration with a day trip tank and a larger one for cruising be advisable. The issue is that keeping a 150 gallon fuel tank full all the time, especially when you might only use 50 gallons on a day trip, requires that you carry 150 gallons of fuel, 1,200lbs, around with you all the time.

With two tanks you have to have a switching system, sending units, filters, and gages for both hense double the potential for mechanical problems.

With a partially full tank that is not used regularly, there is the potential for condensation, and other problems. Any thoughts?

Note: a 125 mile range for Alaska is not enough. For example, if you want to go from Wittier to Motnague Island to fish halibut, you will never get back with only 125 miles worth of fuel. Also it will take you 8 hours to get there and 8 hours to get back at R25 speeds.

[thataway]

I agree with dtol, that 200 to 250 miles is desirable for an Alaskian run from the WA area.

We have usually had several tanks. There are some who feel that it is not all that important to keep tanks full. I cannot keep my tanks full on the TC and no problems with that. I didn't keep my diesels tanks full.
http://www.yachtsurvey.com/myth_of_condensation_in_fuel_tanks.htm
Is an article by David Pascoe on fuel tanks and condensation.

We have only had one boat with a day tank. A day tank is an excellent idea, too bad that more boats don't have them.

Fuel management requires several things--one is preservatives: Stabil or Pri G or D, plus Startron. The second is re-circulation and "polishing" We had a fuel pump and the polishing system in all of our diesel boats, even the racing sailboats with small diesels. The fuel pump can transfer fuel between tanks, it will allow rapid bleeding of the injectors and filters.
Some engines, like the 2 stroke GM diesels and the Ford Lehmans, recirculate the diesel thru the return lines. Some diesels do not recirculate a lot of fuel, and some are not run often. For these engines, it is advisable to run the polishing system regularly to remove algae,(which grow at the water fuel interphase), remove moisture and any impurities in the fuel.

I mentioned in another post that I got salt water in one of my fuel tanks. Having another equal size thank, allowed me to switch to that tank, then filter, remove the water and polish that fuel. Eventually I ran it into the other tank, and pulled the man hole on the tank, so I could get into the bottom and siphon off any debris and then clean the bottom with paper towels, to be sure I had the tank absolutely clean.