[Lucky Dog 33]

Toying with the idea of converting from original 1989 crusaders to diesels. The gassers I have now are original with approx 2200hrs. Motors run ok, but this new to me boat I just don’t trust them. My original plan was to pull them this winter and rebuild them and replace all components (manifolds, risers, water pumps, etc). However with the price of fuel not going down anytime on site and the current fuel burn of estimated 35-38/gph, I’m considering replacing with cummins 6bta 330s. 

I’ve been searching everywhere including boat diesel and Sbmar, but figured I’d post here for a more Tiara perspective. Has anyone every done the conversion? 

Will the existing side exhausts and 1.5” shafts be sufficient?

Can I reuse the 295gal fuel tank? It was replaced at some point in the past. I’d have to dig they receipts to find out exactly when. 


Any crazy modifications needed to mount the motors to stringers?

I would think it should be a fairly easy swap being the 6bta was an option. 

Any info would greatly be appreciated.

[Sans Peur]

I haven't done it but, I owned an older Luhrs 40 that the PO swapped them out on. Went to the Cat 3116's. He used to original.aluminum tanks but thick aluminum plates along the stringers for extra support and swapped the props. It ran pretty well with that setup.

Only thing he didn't do right was go to bigger shafts. I was warned by the surveyor not to bring the throttles up very fast as the shafts were small for the torque and larger sized props on the boat. I was always carefull with it while coming on plane.

The next owner ran the boat for about 6 months and broke a shaft right in front of the prop. Hard to get the prop back in the middle of the gulf stream in a couple thousand feet of water. I had given him the same warning but not sure if he listened.

[August Rush]

I have always been told that this is not as easy as it sounds. Yes, you could use the same fuel tanks but the biggest job will be removing the fuel and then installing return lines. In addition there are other things to consider with exhaust...super critical and a diesel exahust system and gas is not interchangeable.

The real answer is YES, you can do anything with time and money. My guess is your looking at $150k of work if you are paying a shop to do all the work with new engines. You can buy a much newer boat with diesels for less than that...