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Once upon a time there was a poor fishing boat captain who had put all his hopes and dreams - and most of his savings - into a beat up old 31 Bertram. In the process of restoring this boat, he leaned heavily on things that he could do himself, preferably with minimal investment of money. He painted the hull in the water, with a brush, on a day when the tide was abnormally high, so he could sit on the dock and scoot along sides. The interior was painstakingly redone in teak and mahogany paneling, much of it salvaged from older wooden boats beyond saving. A 12,000 BTU marine A/C unit (used), electric head, microwave oven, color TV, stereo, and 12v/110v refrigerator finished out the cabin updates. Fishing equipment salvaged and bartered for was installed, including double spreader outriggers and a classic Rock-a-Way fighting chair. A teak deck was hand built from 1/2 inch planking.
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Things were going pretty well until the issue of repowering raised its ugly head. The boat originally carried gasoline big blocks, with 1:1 transmissions, 1-1/2 inch shafts, short struts, and 12 X 13 inch props. To get decent performance, I - excuse me, I meant the poor captain - would need to replace the transmissions and go to larger props, at the very least.
To stay with gas and really do it right, however, would take a new engine (to match the nearly new 454 on the port side), new gears, larger shafts, bigger struts, and larger props - and . . . require spending some bucks. After all this trouble and expense, he would still have gasoline powerplants, when what he wanted was diesel!
Diesel engines would give the old boat significantly more range, through dramatically improved fuel economy. Since diesels would also require transmissions of at least 1.5 : 1 ratio, larger shafts, and struts large enough to give clearance under the hull for larger props, speed - both top end and at cruise - would be higher, also. The other advantages of diesel - longer engine life, lower maintenance, and increased safety - would be just icing on the cake. The few disadvantages of diesel - the smell of the exhaust and the need to be more careful of fuel quality - would be outweighed just by not having to change spark plugs.
The only real problems this captain had in finalizing the decision to go diesel was the price. New diesels and the related gear are damned expensive! I priced Yanmar, Cummins, Caterpillar, John Deere, and the V-8 truck conversions by Peninsular, Mercruiser and others. I found a range for engines and gears of from $32,000 to $45,000, before taxes and installation. Even figuring that diesel powered 31 Bertrams can sell for $50,000 or more, by the time I invested in new engines, the financial logic would be difficult to justify. Even if I planned to keep the boat forever, payback on new diesels would be a long time coming (except in personal satisfaction, of course). Buying used engines and gears was another option, but is always a gamble.
The answer to my problems seems to be in a new venture by Cascade Manufacturing of Fort Worth, Texas. Cascade has spent the last 2 years developing kits to convert light truck diesel engines to marine use. First in the product line was a conversion of the Ford/International 7.3 liter V-8. These engines are roughly the same size as a big block gasoline engine, but produce more torque for better fuel economy and longer engine life. Engine weight is also similar to a 454 or 440, and in some cases the same transmissions and shafts can be used - making for relatively easy conversions. I have ridden in a 30 foot flybridge sportfisherman powered by Cascade-equipped naturally aspirated 165 hp 7.3's, and was pleasantly surprised at the performance. Gale Banks turbos can add even more power to this engine.
Cascade is currently developing a kit for the newer Ford Powerstroke engine, which puts out 235 - 250 hp and 500 ft. lbs. of torque at peak rpm. The downside to these V-8's is that they are wide engines and operate at fairly high rpm - 3200 to 3600 - but several other companies produce popular marinizations of these engines.
The probable star of the Cascade line is the conversion kit for the 5.9 liter Cummins diesel installed in Dodge trucks. Cummins marinizes this engine as the 6BT and 6BTA, with horsepower ratings from 210 to 315. In this application, the inline 6 cylinder Cummins is one of the more popular marine engines for boats from 30 to 35 feet. The Dodge version in older trucks - up to the 1998 versions - is rated at 185 hp and 440 ft. lbs. of torque at a maximum of 2600 rpm. The 1999 version is a 24 valve powerhouse bumped to 235 hp and 465 ft. lbs. of torque. The reason for "de-tuning" the engine was apparently that the older truck automatic transmissions would not hold up to the extra power. Simple injector pump modifications can boost the truck engine to 300 hp or so.
Cascade's kits include water-cooled marine manifolds, heat exchangers, raw water pump, marine bellhousing, and all necessary brackets and accessories. The manifolds and bellhousing are cast from marine grade aluminum, for strength and light weight. There are several design changes/improvements incorporated in the Cascade version of the 6BT. The raw water pump is located on the back side of the front gear assembly, where the truck power steering pump would mount - making for a gear driven water pump very easy to get to for service. The starter is located high on the bellhousing, making it easy to reach and keeping it out of bilge water. Cascade mounts the heat exchanger and day tank on top of the exhaust manifold instead of in front of the engine as Cummins marine does, and uses a much large unit than is really necessary. The manifold taking air from the turbo into the engine intake has a split delivery instead of the stock single port, to keep the back cylinders from possibly starving for air.
The base engines Cascade starts with are salvaged from wrecking yards - although a new or rebuilt automotive unit would work jut as well. The Cummins price is running anywhere from $2,500 to $3,700 each for low mileage engines, with the Fords costing about the same. The Cummins I am using have 23,000 and 35,000 miles on them. Cascade has located a mechanic who will overhaul the engines - also install the marine gear - but Dodge trucks in commercial service often get 500,000 miles before needing overhauls.
I know a commercial fisherman in Maine who purchased a used (marine) Cummins 6BTA with 15,000 hours on it, and says it runs just fine.
Yes, I'm installing two Cascade converted 6BT's in my Bertram. We'll be using Twin Disc gears of 1.44 : 1 ratio, 1-3/8 inch shafts, and probably 20 x 20 props. As this boat will be a test version available for examination by potential customers, I plan to start out running the engines stock, then make various modifications for performance testing. We will be trying a Cascade designed aftercooler, injector pump modifications, and possibly other design innovations. Of course, the lower horsepower engines will get better fuel economy and have longer effective engine life with less maintenance, and may perform as well as I need for charter and tournament fishing.
The cost of the 2 engines, new transmissions, and Cascade kits should come in at under $20,000 - less than a friend paid for a pair of used marine 6BTA's of 250 hp, with gears. Another friend installed factory fresh 210 hp 6BT's in his 31 Bertram last year, and tells me he cruises 20 knots at 2,000 rpm. With a clean bottom and lightly loaded, this boat can do 27 knots at 2,600 rpm. Fuel economy over his old 440 Chryslers is much improved, to say the least.
Cascade Manufacturing can be reached at 2768 Southeast Loop 820, Ft.
Worth, TX 76140, 817/568-1956 - or visit their webb site: cascademarine.com.