Diesel conversions

TBonedad · Post by **TBonedad** » Mon Dec 19, 2005 10:30 am

Great site! I did a conversion in 2002 and into 2003. My boat is a 1979 33 SF. I bought the boat cheap due to one seized 454 and another right on the verge. When I did the conversion I did things right, but rather inexpensively because I did most of the work myself. Because I did most of the work the project took more than a year. Here's the story: The diesels I used are 1989 Cummins 300 6bta m2's (300 hp forerunner to the 330 b's). I found engines that were "shot" and needed rebuilds. A good friend and I did the work (he is a former Cummins tech and can build 6b's in his sleep). Including buying the "cores," machine shop work and replacing most parts the rebuilds cost just short of $25,000 total. I kept and used the ZF 220A (1.53:1) gears that came with the engines. I upped the shafts from 1 3/8 to 1 1/2. Kept the same struts by using cutlas bearings with a thinner wall. I think I paid $1500 for Aquamet 19. (I may be off by a little bit here, but that's what I remember) The boat had extra fuel added by the previous owner so total capacity is 385 gallons. Getting rid of the gas and cleaning out the tanks was not a real big deal. I have good access to the top of the main tank and was able to pump out the gas, use a towel on a stick to soak as much as possible out of the tank, and then rinse with a few gallons of diesel before re-filling with clean diesel. All new fuel lines. New filtration. (I used Ra-cors) Clean and repaint engine room / bilge. Increase exhausts to 6". New batteries and basic electrical system (I converted to two 4-d cranking batteries and an 8-d house battery, all separate circuits with on/off switches to parallel in emergencies). I added a third air intake scoop on each side (diesels like a LOT of fresh air, especially in Southeast Georgia in the summer). In hindsight I should have put vents into the hullsides and closed the holes on top of the gunwhales. This would have required glass work and more than I wanted to get into at the time. I started with 21 x 21 4 blade props, but took out 1" of pitch this year because I was barely making full RPMs when I loaded for fishing. Now I make rated plus with a full load. I'm very pleased with the results. Hindsight being what it is, however, I would have done a few things differently. I'll get into a few of those later. I get a little smoke at startup. Block heaters help some, but don't totally eliminate the smoke and smell (I kind of like the smell of a diesel anyway). Because these are older engines with mechanical fuel pumps there's not much I can do to totally eliminate the smoke. When running and after the engines have warmed up the smoke is very light (really undetectable when running). As far as smell, a few whiffs in the cockpit if the wind is right but not bad even to my wife's sensitive nose. Cruise speed is one area I expected more than I got. I cruise an honest 18 kts @ 2400 rpm when fully loaded (385 gal fuel, 6 grown men, 200 - 300# ice, beer, etc, fishing gear, full water tank, etc. High cruise is 20 kts and 2600 rpm, and WOT is 23-24 kts @ 2800 rpm. I'm pleased enough, since 18 to 20 kts fits the sea conditions most of the time, but who wouldn't like to be able to cruise 25 kts? Things I might do differently include holding out for higher horsepower engines (370 hp Cummins seems like the ideal) and modifying the engine room air intakes to draw through the side of the hull. All-in-all I am happy with the results and I REALLY know this boat inside and out now. Projects to come include replacing a leaky forward skylight / hatch, re-bedding bow rails, modifying the bridge for flush-mount electronics .......... I would be happy to talk with anyone else considering this type of project. Fraser

Post by **dougl33** » Mon Dec 19, 2005 11:31 am

Welcome aboard Fraser. Great first post! I'm surprised you're not getting more cruise speed out of the 300hp 5.9's. You're doing pretty much the same as what the factory installed Cat guys (260-270hp) are doing, but with a lot less weight. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA

franklyprice · Post by **franklyprice** » Mon Dec 19, 2005 1:12 pm

Frazer, Glad to have another" hands on" type guy on board. Doing what you did without spending more money gives me incentive to do something like that. As much as I'd like to believe I can afford the 60K plus for new engines etc., it's probably not going to happen. I could almost see myself being able to do what you did.. As Doug mentuioned , I'm also a little surprised you're not getting more speed out of her. The guys I've talked to that put in the 330horse cummins are cruising at about 23 KTS. That extra 60 horses can't make that much difference. Do you know what kind of fuel you burn per hour at 18 KTS? Frank Price

Capt. Ed · Post by **Capt. Ed** » Mon Dec 19, 2005 7:58 pm

Frank (Tbonedad), great post for anyone thinking about converting! Thanks Have you checked the RPM at the engine to be sure the tach's are correct? 1979 Bertram 33' FBC ALEXANDRA Port Richey, Florida

TBonedad · Post by **TBonedad** » Tue Dec 20, 2005 3:13 am

Thanks for the welcome. As to your comments and questions: I was a little disappointed in my speed numbers, also. I have checked out the engines pretty thoroughly. I've used a phototach to calibrate my onboard tachs, installed boost and exhaust gas temp gauges, etc. so I can confirm that the engines are making power and rpm's. I have wondered if changing the gear ratio and prop combination would make a difference, but it gets expensive to monkey with that stuff without some real assurance that the results will be there. One answer to the speeds like the factory cats get may be the extra 125 gallons of fuel I carry under the cabin sole. Since I have had to prop for the weight, even when the weight is gone the boat is still propped to carry it. When she's light cruise speed does go up about a knot across the rpm range. I also don't want to be misleading on the total cost of the conversion. When all the dust settled I was in for close to $50,000. Certainly cheaper than the $70k to $90k that seem to be realistic estimates for having a yard install new power, but still a pretty significant outlay. In hindsight I would have to consider letting a good yard do the work and buying new or reman engines with warranty. I know I did more to the boat than they would have (which added some cost), and I enjoyed the project and results, and I know everything was done right. Still, having some backup if something goes "boom" would be nice (500 hours with no problems, though). Not to mention my own time invested. Fraser

jav · Post by **jav** » Tue Dec 20, 2005 4:03 am

Tbonedad, great post. With that much fuel onboard, I'll bet your range is phenominal! Plan on fishing in the Azores?- LOL. It sounds like you really went the extra mile to safeguard your engines by propping for a true full load which is pretty smart and safe. I was a little more concerned with speed and economy so I propped a little more aggressively - which I knew was not the smartest or safest approach. When I did my conversion (not on a Bert) I also built in some extra fuel capacity but I only planned on using that capacity about 10% of the time. 90% of the time I fill my tank to around 5/8-3/4 full and refill when it gets below 1/4. With that I still have about 50% more range than when it was gas powered and fully loaded with fuel. I propped to achieve WOT + 50 @ 3/4 tank with 4 people/gear aboard. I also used larger 3 blade props to pick up a little more efficiency. Between the weight savings and propping, I'd bet this apporach was worth 2 knots over the entire range and some fuel savings to boot. I also find that when I run truelly full, my stern squat and wake are just huge and not condusive to speed or economy so I don't do it unless I really need to. I don't know about the B33 but my boat doesn't feel fully on step until it gets to 22-23 knots which I just can't do with more than 1/2 a tank of fuel.