Gas to diesel

franktamdan · Post by **franktamdan** » Tue Dec 09, 2008 8:20 pm

Hello, I want to change my 454's to 3208 n's. Will the motors pretty much fit where the 454's were or do I have to do alot of modification? HELP!

Post by **dougl33** » Wed Dec 10, 2008 4:57 am

Frank, Welcome aboard. Tell us a little about your boat. The 3208N's will fit no problem as the 3208T was the diesel option for the 33's. Are you sure you want to go with the naturals? The boat will be mighty slow and re-sale would be a bitch.

lwrenn · Post by **lwrenn** » Fri Dec 12, 2008 4:08 am

If I was going to do this I would go for the speed! The 3208 are heavy and there are other choices that I would look at. Unless you have two 3208's with gears and gauges etc. Does the gas 454s use the same twin disc 502 gears? If so you got some of the battle fought. Another question when the boat hull was molded was there a difference in the stringers for the gas boats. I have seen some Bertram 33s that the stringers look thinner than others. Captain Larry Wren 305-360-4900 www.apirateschoice.com [img]http://www.bertram33.com/photogallery/p ... Choice.jpg[/img]

Post by **dougl33** » Fri Dec 12, 2008 6:28 am

Larry, The gas boats used bw gears. Anything prior to 1987 used a 2:1 ratio and 21 inch diameter props. 1987 and up used a 2.5 ratio and 23 inch props. From what I've seen there's no difference in the stringer size.

lobsta1 · Post by **lobsta1** » Fri Dec 12, 2008 7:12 am

quote:Originally posted by dougl33 Larry, The gas boats used bw gears. Anything prior to 1987 used a 2:1 ratio and 21 inch diameter props. 1987 and up used a 2.5 ratio and 23 inch props. From what I've seen there's no difference in the stringer size. Regards, Doug L. 1986 33 Bertram FBC Cummins 6BTA's Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img] Sorry Doug, Another blanket statement that does not apply to older B33's. I am just as guilty of making them as anyone else. I have the 1:91 > 1 gears. Don't know about the 2:1 trannies, but the gearset I have, that makes the port motor the reverse rotation one. Al

Post by **dougl33** » Fri Dec 12, 2008 8:36 am

Al, When I say 2:1, I meant 1:9:1 because its a close enough evaluation. For instance, if you use boatdiesel's prop calculator I don' think it lets you use 1.9:1, so I've been used to saying 2:1 to anyone that asks. Most props shops I've dealt with will round it up as well. For the record, when I had gas I also had 1.9:1's. As did all pre-87 gas boats. Sorry for not being my usual more precise self![:D] You guys coming tomorrow night?

lobsta1 · Post by **lobsta1** » Fri Dec 12, 2008 12:06 pm

Doug, We'll be there. Sorry about the correction. Reason I mentioned it is I "think" 2:1 trannies would then put the opposite rotation engine on the stb side. If I'm wrong, then someone correct me. Al

jeff · Post by **jeff** » Fri Dec 12, 2008 1:12 pm

Hi Frank, welcome aboard. There is a lot of diesel conversion information on this site if you take the time to dig it out. I, like several others here converted to diesel. My choice was Cummins 6bta's and I would not think of anything else. Honestly 3208 would be my last choice. Good motors, but heavy and not as fuel efficient as some of the 6 cyl. motors. Also the fit of the 6 cyl. motorts gives you a lot of working room. I can get on the "outboard side" of my engines for maintenance or repair. I don't think you could do that with V-8's. The 300-315 HP motors give you all the power you need and will cruise 22-24 KT. You will have to replace transmissions and all engine related hardware. It get's expensive but worth it in the long run.