I got a question earlier this year that essentially asked: I can’t quite reach full rated RPM under load but I’m only 50 to 100 RPM low in my Bayliner 4788. I’m considering playing it safe and repitching my props but my dealer recommends that I not bother until next season.  Is it OK to wait until next year since I’m close to correct and don’t run the boat hard for long periods of time?

My response:

When giving other people advice, I'm conservative.  Having spent 6 or 7 years servicing cars professionally, I know just how upset a customer can get when you say "it'll be OK” and it ends up not being.  The safe answer is to remove 1" of pitch.

However, you aren't nearly in as bad shape as many 4788s.  Since you clearly care and have a good strong set of engines to start with, invest up front in great instrumentation.  Buy boost gauges, pyrometers, and digital tachs.  Boost gauges and pyrometers provide valuable engine load information to help avoid overload (http://www.mvdirona.com/TechnicalArticles/DieselEngineOverload/Default.htm). The standard Faria tachs tell you when the engines are running but not much more—get good digital tachometers (http://www.mvdirona.com/TechnicalArticles/DigitalTachometer.htm).  Also get the fuel curves for your engine from the local distributor or the Cummins marine support team (wave.master@cummins.com).  From the fuel curves sheet you'll see exhaust gas temp at full rated RPM.  It'll be around 850F.  My general rule is to not cross that line although many argue this is unnecessarily conservative.  Some engines have acceptable load levels that produce exhaust temperatures above those at rated RPM. I chose to avoid this condition entirely.

The right answer is to do both: 1) get the instruments I recommend above and 2) re-pitch right away.  However, if you are careful, don't run hard, and watch the instruments, you'll probably be fine running with the current pitch.  The pyro's will tell you for sure. 

I needed to take out a second inch of pitch in mine, but since I'm both careful and cheap, I didn't want to re-pitch the second time right away. Instead I did three things: 1) ran light at lower RPM, 2) watched the pyros and didn’t ever go over the max rated temp (I prefer it 50F under), and 3) read the fuel burn.  From fuel burn you'll know the HP you’re consuming at cruise.  With your engines, multiply gallons/hour/engine * 19 and you'll find how much HP you’re asking for at cruise.  The constant 19 is the horsepower produced per gallon per hour and it’s very constant across all high speed diesels.  Newer common rail engines are closer to 20 HP/gal/hour but these numbers are remarkably stable across all manufacturers.  I was introduced to this approach by Tony Athens (http://www.sbmar.com/Articles.cfm).  Ensuring the HP you are using is always less than the manufacturer performance curves at that RPM will ensure that you are not overloaded.

In your case, I lean slightly towards re-pitch now. That way you can get to know the boat with everything running correctly.

James Hamilton

jrh@mvdirona.com

http://www.mvdirona.com/

I get the odd query, and this one is perhaps of broader interest.

Gerald Albertson wrote:

Hi James and Jennifer,

I absolutely love your pics, especially Desolation Sound at Christmastime.

It is a fine goal that I obtain the proper skills and confidence to do an Around-Vancouver Island adventure one day.

One of the next additions that I plan on making is the digital tachs that you describe.

My 34 Tollycraft has 210 hp 5.9 Cummins diesels of late 1988 manufacture….turbocharged but not aftercooled.

My neighbor has a 37 Nordic Tug that has a Cummins diesel (approx 350 hp) and it came with a block heater.  I think his is a simple headbolt heater as opposed to a tank heater, but I’m not sure about that. 

Anyway, I thought the block heaters might be a nice addition to my boat.  What do you think?

James’ response:

We don't chose to use block heaters on Dirona but they are a good option to increase engine longevity (cold start with cold oil is hard on them) and to warm the engines and engine rooms (decreases condensation and reduces rust).  Mechanically injected engines such as ours tend to smoke a bit when cold, and a block heater can reduce cold start smoke markedly.

Cummins sells core plug block heaters.  These are installed by removing an engine block core plug and inserting a block heater to take its place. They heat the coolant and it circulates by convection.

Another solution I've seen  is a pump and heater in the coolant.  A variant of that used in over-the-road applications uses a diesel furnace to heat coolant (and heat the cab) when the engine isn't running.  This allows the cab heater to function when the engine isn't running, and warms the engines.

A common installation I've heard used successfully in Cummins marine applications is Wolverine oil pan heaters: http://www.wolverineheater.com/.  They are used by Seaboard Marine extensively on Cummins with good success: http://www.sbmar.com/. They sell at reasonable prices and can offer wattage advice for your conditions.

            -jrh

James Hamilton

jrh@mvdirona.com

http://mvdirona.com

The Seattle Boat Show seminar schedule has just been posted. We’ll be presenting on the red stage at 4:15 on Saturday February 2^nd. Our presentation will include highlights from our upcoming Waggoner sister publication Cruising the Secret Coast: Unexplored Anchorages on British Columbia’s Inside Passage.

While docked in La Conner recently, we were fortunate to walk past the Pacific Mariner plant at just the right time. They were wheeling a huge, empty hull, likely of a Pacific Mariner 85, around the building. It appears that they mold the hulls on one side of their property, then transport them to the other side for completion. Another large boat looking near completion was next to the slot where this one was destined.

The tractor operator did an amazing job—the clearance at many points was barely inches.

On a recent trip from Elliott Bay to Mats Mats Bay, we passed the Washington State fast ferry Snohomish running south. The last we’d heard, the ferry was still mothballed in Eagle Harbor. A successful lawsuit by Rich Passage residents had taken the passenger-only Snohomish and its sister ship, the Chinook, out of service to prevent further erosion caused by their wakes. Both are to be sold.

When we saw the Snohomish that day, it was in temporary service between Port Townsend and Seattle. The two 80-year-old ferries on the run between Port Townsend and Keystone recently had been condemned, and no other car ferries in the fleet had a shallow enough draft to negotiate the approach to Keystone.

With gale force winds forecast for the Strait of Juan de Fuca, we anchored last night in Watmough Bay at the southeast tip of Lopez Island. The bay appears to have good protection from southeast weather, but we saw exactly the same winds as at unprotected Smith Island at the eastern end of the strait: steady winds above 30 knots with gusts to 54. This is the highest winds we’ve seen at anchor. The wind speed slightly topped the 52-knot gusts we saw in Pender Harbour a couple of winters back that blew our patio table overboard.

The waves certainly were much smaller than out in the strait, but big waves rolled into the anchorage all night, tossing our boat and making for a sleepless night for both of us. Our 66-lb Bruce held well with a 6:1 all-chain scope, and boy, was it in there when we left.

Diesel engines have a great reputation for incredible longevity, yet most recreational marine diesels fail well before they should. The two primary killers are 1) overload (discussed at Diesel Engine Overload and Tony Athens’ Engine Life vs. Engine Loading) and 2) poor maintenance & operating conditions. Both are easy to avoid with a bit of knowledge, particularly overload.

On the second big killer, poor maintenance and operating conditions, it’s clear that a high quality scheduled maintenance program is a good investment. Beyond that I’ve adopted two simple techniques that have really paid off for me: 1) spend a bit of time with the engines, and 2) know your specific engine’s weaknesses and failure modes.

For the first one, just spend time in the engine room. If you know what it should smell like down there, what sounds are normal, and you frequently visually inspect, it’s amazing what you will find before it becomes a dangerous problem. From spending just 30 seconds in the engine room each day, I’ve found a variety of problems that could have become more serious. For example, the support bracket for the engine-coolant header tank broke once. At that point, the header tank was hanging from the hoses. If the hoses break or abrade, there is a good chance the engines will overheat, one of the quickest ways to shorten diesel engine life. Spotting this early means it’s a complete non-issue. In another engine room sniff, I smelled diesel. It never smells like diesel down there, so I looked more closely and found a fuel-tank vent-hose clamp had rusted through. If you keep the engine room clean and well lit, any leak from any component can be seen quickly. I’ve had several raw water pump failures, each of which was proceeded with a raw water leak at the pump seal (Changing the Raw Water Pump). Catching these problems early keeps the engines safe.

The second of my two simple techniques is to know your engines and their failure modes. This one also is incredibly easy. Find a forum where your engines are broadly discussed. For Cummins Marine, Boat Diesel is an excellent resource. From reading about your engines, you’ll start to learn the weak points and where a little extra attention is well worth paying. In the Cummins B-Series engines, I keep a close eye on the raw water pump and engine accessory-drive belt-idler pulley. Both fail more frequently than they should and warrant a bit more attention. I just posted a short article on checking the engine accessory drive belt and idler pulley: Belts and Idler Pulley.

James Hamilton

jrh@mvdirona.com

http://mvdirona.com

Those of us with recent Cummins engines (since they started using air preheaters) will notice that the factory alternators are actually pretty respectable.  My 2000 270Bs come with 105A Delco alternators. You would think this means I can charge at over 200A with the two installed in Dirona.  Well, it turns out that the 105A specification is more of a marketing number than an engineering specification.  Yes, they can produce 105A of output.  However, they can’t do this for more than a few minutes at a time, which is close to useless.  Now that we know that they can’t really produce 105A continuously, what can they do? 

Sometime back I wrote up an article investigating what charging rates can be produced continuously and reliably and how to achieve that number at minimum cost and hassle.  It was published in the May 2007 PassageMaker and we just put it up online at: http://www.mvdirona.com/TechnicalArticles/ChargingSystem.htm.  I’ve found that you can reliably get 70 to 80A and the alternators will run trouble free for years configured that way.  The article documents the investigation, discusses the limiting factors and shows how to configure your charging systems to get good results.

                                    --jrh