Gas to Diesel Conversion?

[Lotsa Luck]

I have a 1998 32 Convertible with Marine Power 454s. I really like my boat but wish it had diesels for better fuel economy and longivity. Before gas prices went to hell I had planned to sell it and move up to maybe a little bigger with diesels. But trying to sell this even though it looks great will probably be impossible. Next option would be to repower. While I haven't looked into costs I'm guessing $75K? Doing this, I would plan to keep the boat much longer and that's ok with me. Has anyone done this and how bad a nightmare is it? Any recommended diesel for replacement. I was thinking cummins.

[dnkstarr]

I had a 97 320 open, with marine power. I looked at repower options as well but decided to trade up, but that was before fuel prices went up. Anyway, I looked at Yanmar and Cummins both ran about 25k to 30k each then there was the "other" work. You will probably need to change the seawater intake to 2" and add strainers. You probably have 1.25 inch shafts and will want to go to at least 2" that means new props, shafts, seals, and cutless bearings, they may be able to mill out your struts. Dont forget the motor mounts will need to be changed. The good news is the marine power engines already have a fuel return line so no additional holes will be necessary in the tank. The final rough number I was able to put together was around 90K to 100K that was in South Florida. If you plan to keep you boat, at least you know what you have, go for it. If you think you may want to trade up at least list your boat as I did and see what happens. Just a suggestion, Hope this helps.


PS I have the cummins in a 36 now and love the engines.


David

[kcummin]

LotsaLuck,

I just repowered my T350 this past winter...Like you I was happy with my boat, just needed more range, speed, and efficiency. Considered taking the hit trying to sell the gasser, and then taking another hit buying a diesel boat. Economics worked best for me to repower. It's an individual choice based on your wants/needs.

It is a different boat with the diesels, and I know all the systems inside out, which is peace of mind when offshore.

You can figure on 80-100K, by the time you figure (2) Engines, Trannys, Generator, new plumbing, gauges, wiring, labor, etc. I also did floscans, oil exchangers, turbocators, and CCV's while I was at it.

I was able to reuse my 1.5" shafts, and 3-blade props, but will be changing to more efficient props this winter.

Look at the Cummins Recon's, basically brand new mechanical engines, with new engine warranty (extendable to 5 years). Recons cannot be sold in new boats because of the Tier-2 regulations, but perfect for repowers.

Take a look at Boatdiesel.com, and study, study, study before you make the move. Lots of good information there about fuel filtration systems, and especially exhaust system design that you need to consider in the repower.

Hope this helps

Kevin

[Lotsa Luck]

Thanks David and Kevin, I appreciate your insight and comments. I think I'll search for the recon lines and do some rough calcs on costs. I also met with a shop today that has done many repowers and had a good feel from them. He also suggested recons or used and go through them. Lots to think about. Thanks again.
Don

[CrazyIslandMoFo]

kcummin, when you say " diffrent boat " I'm just wondering in what ways... I run diesels in all my trucks. Love diesel power! Sadly my lurhs has gas... the repower is very tempting, wouldn't be cleaner to serch for one with diesels allready on board?? pro's like range and cruse spd, would be great to know, does she "bob" in the water any diffrent?... what about niose levels?? my gas are not the most quiet... are there any cons to changing to diesels other than cost??... Would you mind taking a few moments to enlighten us?:patriot:

[kcummin]

CIMF,
First of all let me say, that I believed my 35' was severely underpowered with the 330HP 454's. It always felt that I needed to push the engines too hard to get the hull running at its best position. This of course means that fuel economy is out the window, which matches David Pascoe's review of the boat.

With the gas engines running at a reasonable speed (but not hull optimum) speed (3300-3500), the lack of torque was noticeable. Lots of beam wave roll, and the gas engines RPM dropped considerably when climbing the back of waves.

With the diesels it is a different boat. You set the RPM's and forget it. The diesel governor keeps those rpms the same. If anything, when I get into a chop, I have to pull the throttle back, becuse it wants to fly right over the top on the waves.
Also when starting out she kicks right up on to plane very easily, and my cruise is an easy 400-600RPMs off the top and the diesel engines seems to be purring along, nowhere near the top end needed for efficient hull speed. This of course has it's advantages in fuel economy, range, and hopefully less wear/tear on the engines.

I also get much less roll on beam wave situations, and am thinking that may be attributable to the the added weight of the diesels below the water line, which mayhave lowered my overall center of gravity thereby increasing the lateral stability.

Another nice advantage when docking...Don't need to touch those throttles that now stay in idle. When I hit the shifters..She MOVES! Now I need to keep her mostly in nuetral and shift into gear for short periods of time. Much different from the same boat with gas engines, where I needed to goose the gas. Tranny ratios went from 2.5:1 with gas to 1.5:1 with diesel.

As to the noise, I would have to say it is about the same if not slightly lower moise with the diesels. This surprised me , because I thought they would be much louder. My installer, put in straight mufflers, and we also used an inline flapper valve in the exhaust system to prevent water backflow. We also used the Tony Athens (Boatdiesel.com) style dry exhaust riser setup to make sure that when the engines are off, ALL water drains from the system.

This is only one man's experience, maybe there are others that will chime in on there conversions or trade up experiences.

Hope this helps you.

Kevin

[CrazyIslandMoFo]

Thank you Kevin. I was courious about the weight, what you say seems right to me, Your 35' with 330's would seem a little sluggish since the same moters in the 29' are ??? I may have 300's (not able to confirm).I will seriously be cosidering diesels. I love my boat now, to add a windshield & diesels... I may be in the market for a trade up ... Thanks again for your great info!