Gas vs Diesel

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  • JimG
    Senior Member
    • Mar 2005
    • 123

    I looked around briefly right after buying my boat and found I could get a new "compatible" diesel for about $8K, deklivered. If you don't install it yourself, it might be another $5K or so, depending on the boat.

    Don can estimate a rebuild, but I'm sure it's less than 1/3 that total. There are a lot of serviceable A4s for sale (from other people that listen to the "convert to diesel" drum) on craigslist, ebay, etc for less than a rebuild.
    S/V Latis
    Brookings, OR
    Ranger 33


    • Jesse Delanoy
      Afourian MVP
      • Dec 2006
      • 236

      We've had a 1977 Catalina 30, with original Atomic 4, for six years. With minor issues, the engine has generally been reliable. Last summer, in the middle of dealing with some water-in-the-oil problems, we discovered we had a bad bearing, and decided to repower.

      The whole project, including a new, rebuilt engine from Moyer Marine, and installation at Zahniser's in Solomon's Maryland, ran about $10,000, much cheaper that a diesel retrofit would have cost, plus I still have the excess horsepower that an A-4 provides over a 16 hp diesel. Best of all, over the five previous years, I've learned how to do a lot of maintenance on the engine, learning that will be put to good use in keeping the new one running smooth.

      Don and Ken were tremendous help to me throughout the entire process.


      • hd78half
        Senior Member
        • Jan 2007
        • 16

        A4 vs Diesel

        Had to join in.

        Have used the A4 for 16 years w/o any problems. Am rebuilding it now only because we've gutted the interior for an upgrade, and it's a great time to pull and re-install the motor.

        Am doing all the engine work myself. Parts for the rebuild and some minor upgrades (electronic ignition) purchased from Moyer at $680.00. Minor parts from hardward store (paint, nuts & bolts, hose, etc) another $100.00. Machine shop charge to perform precise measurements on the crank, camshaft, rods, bearings, cylinders, and hone the cylinders was $95.00

        Marina fees will be only the use of the travelift for hoisting engine out and dropping it back in are $75.00 each time, total $150.00. This was ultimately easier, for the money, then trying to use the boom.

        Found the A4 extremely easy to disassemble and am expecting no problems during re-assembly. Very simple engine.

        Gas is cheaper than diesel, and smells better. Diesel fuel injectors, filters, etc. are expensive and hard to work on.

        My vote for Great Lakes, coastal and Caribbean cruising: the A4.


        • Bacchanal
          Frequent Contributor
          • Oct 2004
          • 9

          I chose the A4

          I went through your exact deliberation a year ago. The cost difference was the big driver for me. For the marina to install a new Yanmar and hand me back my boat was going to cost about $16K (new exhaust, controls, gauges, etc.) and for me to repower with an A4, where I do most of the work myself, the total cost is going to be around $7K (new cables, hoses, alternator, fresh water cooling, etc.) For $9K I can spend a lot of weekends getting this done. I'm still struggling with the changes I want to make. It's the usual, "While I'm at it" thing where the to-do list gets longer rather than shorter, but it will be worth it. We had the A4 for 40 years and 2 rebuilds and it was always reliable.


          • policecentral
            Senior Member
            • Jun 2007
            • 56

            Keep your A-4

            Watch out, you are on an Atomic-4 Lover's site. But, in my experience with almost 30 years with an A-4, you should definitely stay with it. I, with MM wonderful help recently repowered my Ranger 30 with an A-4 that is older than original, but in better shape. Everything fit and no surprises that are always encountered when repowering with diesel. Also, diesel smells, the fuel gets moldy, and the engine is heavier than your A-4.

            All the talk about "gasoline danger" is nonsense.



            • seagrave79
              Frequent Contributor
              • Jul 2006
              • 9

              One Really Good Reason

              Though I have had my doubts over the past year, I would now say, Keep the A4. In addition to all the reasons given above, here's my main one: I can work on it. After the work I have now done and the improvement in performance I have seen, I am reasonably confident that I can do most repairs on my little engine. And as long as I could get to a phone, I think I could manage just about everything up to and including a major fix. I couldn't say that with a diesel. For a cruiser, that's important.

              Just make sure you have your spares.

              1969 Pearson Coaster #114


              • Jlmatt
                Senior Member
                • Dec 2006
                • 72

                Hello everyone. my goal ultimately is to go blue water ocean crossing at some point. And when I sit here, trying to imagine the worst and how I would handle it, I have to say that if I were to go through the kind of storm where the boat is like in a washing machine, I would worry about gasoline leaking. Should I go with diesel then? What a pain, and expensive. I think I'm leaning toward keeping the A4 because I think I'm able to work on it with my limited mechanical knowledge. If I inspect everything, all the hoses and tubings, connectors and clamps regularly and if I try to stay very aware that gasoline is indeed extremely flamable,I think I can keep it safe. I would rather spend the money on sails and rigging.

                Jean-Luc, Pearson Triton.
                1961 Pearson Triton, "Daphnis"


                • Concord
                  Senior Member
                  • Jun 2008
                  • 72

                  I have had both

                  My last boat had a Yanmar 1GM10 and my current boat has an Atomic 4.

                  My recomendation is to make sure you understand whatever engine you decide on. I had a problem with my 1GM10 and called the local Yanmar mechanic and he tried to start the engine with ether and did more damage than good. I was fortunate to find the best Diesel Mechanic around (aka The Diesel Doctor) to help me get the engine back in shape. It turned out that the original problem was fuel related and the ether ended up cracking the piston. The repair ended up being around $600 but the engine was small (1 piston) and the DD cut me a break because I pulled the engine and brought it to him (not an easy task while at anchor). Through the process I ended up learning more about diesel engines than I ever wanted to know.

                  So far I am very happy with the atomic 4, diagnosis and repair seems to be easier than on the diesel. There is also more support around for trouble shooting the A4 than the diesel. Don (The Atomic Doctor) is a great resource and can provide the support to keep you going.

                  The marine environment is tough on fuel especially in a sailboat where the fuel lasts a long time. Gas or Diesel you need to make sure you take care of your fuel. If you don't burn a full tank over a season then it would be wise to drain the fuel and start fresh.

                  Good luck


                  • msauntry
                    • May 2008
                    • 507

                    I'll throw in my two cents even though its an old post, it still gets read alot.
                    Gas engines are easier for the average person to learn to work on, though diesel engines aren't that much harder. If you're travelling long distances, whatever is in your boat, you better know it well because sooner or later you're gonna be fixing it yourself. The advantage of these Atomic 4's is the support available, as odd as it sounds for such an old, out of production engine. There have been so many things learned over the years, and so many kits available to improve weak points, that there is nothing you have to do that hasn't been done before and is probably written up somewhere on this very site.

                    I read about people thinking of repowering because their 10 year old diesel is not running well, and I wonder that my roughly 40 year old engine is still running well. It seems for reliability sake, get a cast-iron engine, be it either gas or diesel. Aluminum ones don't tolerate abuse like the iron ones do.


                    • CowboyPhD
                      Senior Member
                      • Apr 2006
                      • 44

                      Hey hd78half-

                      Do you have that list of parts you bought to rebuild? I'm tearing down an old A4 in my shop and preparing to rebuild. I could use some advice. What machining services did you have done? What were you able to do yourself? What would you have done differently? Etc.?



                      • Marian Claire
                        Afourian MVP
                        • Aug 2007
                        • 1769

                        Rebuild ?s

                        I just finished my rebuild so thought I would jump in with some info. I bought new pistons .010 over, rings, valves, valve springs, keepers, main bearings .010, rod bearings .010, cam bearings, wrist pin bushings, gasket set, and manual. The machine shop cleaned, surfaced, bored and honed the block, ground the crank, surfaced the head, reface seats and lifters and recondition rods. Also had them balance the crank assembly. Due to my intended use I chose to error on the safe side.
                        All the disassembly and reassembly I did myself. I had a mechanic friend who showed me some tricks, ring installation, proper torque technique, etc. Also used the forum and Don on the tech line.
                        Enjoyed the whole experience. Some advice.

                        1 Learn the language. I made mistakes in ordering and with the machine shop due to my lack of vocabulary.

                        2 Clean Clean Clean Even after cooking the head, block and manifold I pressure washed, use a washer with HOT water, cooking only does so much.

                        3 The manual is great. Go slow and reread.

                        I pulled the gas tank while the engine was out and cleaned it but that’s another story.


                        • LarryBud
                          • Jul 2008
                          • 4

                          Advice worth the price

                          We just bought a 1974 Ericson 35-2 after going through the standard years of thinking and dreaming, months of looking at boats, and months of asking experienced sailors for advice on what to avoid in buying a used boat. I have to admit I was looking for a diesel, and that was based on all the free advice from all sources, but we still ended up with an Atomic 4 because I liked the boat so much.

                          After reading this forum I have to wonder where all the advisors are getting their intelligence. I've spent many hours on a friend's Seidleman 37 and when that diesel starts up it is very noisy, and smelly. What a difference with my Atomic 4; and mine is in the middle of the cabin. In my younger days I never took my car to a mechanic for repairs - did them myself. Now days the car is way to complicated, but that Atomic 4 sure looks a lot like that flat head in a 1949 Ford.

                          Through dumb luck, I think I ended up with the best engine for my needs and my boat. I wish I had seen this thread before I when shopping, would have saved me some anxiety. Next time I have a friend shopping for a sailboat I'll send them to this forum.


                          • tony s.
                            • Feb 2009
                            • 3


                            Sorry Folks,

                            This is a little off topic.

                            I am sure that there is a reason why I haven't heard anything about converting A-4s from gasoline to propane burning but can someone fill me in?


                            Tony s.


                            • jeffgerritsen
                              Senior Member
                              • Dec 2008
                              • 37

                              gas / diesel

                              Hey guys,
                              thanks for all the replies. I have a 1976 Pearson 35 with an A4. At 750 hrs on the rebuild, I'm thinking this is a mid time engine, so I'm going through the gas vs diesel repower mental exercise. From what I'm reading on this thread, its thumbs up on staying with the A4 and performing whatever major maintenance is needed, if any. It will sure save me a lot of money staying with the A4.

                              BTW, for serious blue water crusing, whats the problem with gas, other than storing a suficient quantity between ports of call? From what I've read I can't find any. Anyone want to chime in with their two cents worth?

                              Regarding the safety of gas vs diesel, well I'm more concerned about propane fuel used in cooking than gasoline used in vessel propulsion. Saftey records seem to bear this conclusion out.



                              • jeffgerritsen
                                Senior Member
                                • Dec 2008
                                • 37

                                Propane conversion

                                Originally posted by tony s. View Post
                                Sorry Folks,

                                This is a little off topic.

                                I am sure that there is a reason why I haven't heard anything about converting A-4s from gasoline to propane burning but can someone fill me in?


                                Tony s.
                                Tony, I'll answer your question with an honest question I have. Why would you want to convert from gasoline to propane in light of the following statements?

                                Propane has less BTU's per unit of measure (91,500 vs 115,000 per gallon).

                                Propane has more safety concerns, requiring more techno gizmo's for monitoring, thus adding more points of possible failure than gasoline.

                                Finally, Propane can cheat on the ultimate safety test of all, the sniff test, using our standard issue olfactory organ -- the nose!