• If this is your first visit to the iboats.com Boating Forums, be sure to check out the FAQ. To post a question or comment, begin by signing up. To start viewing messages, select the forum that you want to visit from the selection below.

Announcement

Collapse

Help Tip: If you have a question that has not been answered to your satisfaction in the archives, it is always best to start a new thread of your own. By starting your own thread, you will receive the maximum number of views by forum members.

Below are some additional forum policies in hopes of all iboats members will follow, Thank you.

1. Please do not reply to old topics or hijack existing topics. Old topics of a technical nature are like a library book, Please do not write in them.

2. Old topics should be considered archives and used for reference only. Please do not reply to them.

3. Do not take over someone else’s topic (aka hijack) with your own question, even if it is similar. If you have a question that has not been covered to your satisfaction in the archives, it is always best to start a new topic of your own.

4. If you have a question for the original poster (OP) and the topic is over 30 days old, send the OP a PM, he may not even visit the forums any longer, or may not notice your question in the old topic.

5. By starting your own topic, you will receive the maximum number of views by forum helpers that may not even notice your question when it’s posted at the end of someone else’s topic. And those answers will be specific to your particular issue.

6. Please do not post to topics that have been inactive for more than 3 months unless you are the original poster. We have very active forums and any topic that remains inactive for that long should be considered "dead". It is especially confusing when there is an entirely new question posted to an old topic.

7. Posting at the end of any topic is considered to be hijacking the original posters topic which in turn subjects the topic to be closed if it continues to happen thus not making it fair to the original poster in the future had for some reason he/she needed to return for additional information or provide an update of the problem solved which is always welcomed within a reasonable amount of time frame.

8. Please note that you should see a red banner pop up near the bottom of each inactive topic asking you not to reply to old topics. The Red banner will read: Please note this topic has been inactive for 90 days. For the best results, please start a new topic.

Thank you all in advance for doing your part in helping iboats run a smooth ship.

Additional forum rules linked below.
http://forums.iboats.com/forum-rules-guidelines-405/
See more
See less

can you convert a carburated motor to EFI?

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts


  • can you convert a carburated motor to EFI?

    I have a 1978 26 foot Uniflite sedan with a small block 350 chevy and a velvet drive transmission. Last year, I rebuilt the motor and I've put about 50 hours on it. The motor runs great and it performs well I'd say for an eight thousand pound boat. It will do about 28-30 wot and I cruise about 18-22. You may ask "what's the problem?" The problem is that I am a red-blooded American and I want more. It's not that I want to impress anyone, I would really like to be able to cruise at about 25-28 somewhat efficiently.
    I've thought about converting to a big block or even possibly diesel. I think, however, an EFI small block probably would be best because I am so close to my goal already and it wouldn't mean adding any more weight to speak of. That's where my question lies. I have a good motor, but don't know the details of what putting an EFI would be. I am sure it is probably possible, but is it probable? Should I just look for an EFI 350? I would say that I am handy, being the owner of an excavation company, but I am by no means a certified mechanic. I would really appreciate any advice on what should I be looking for etc. If it matters at all I do have an 87' 350 out of a Trophy that I am rebuilding.

    Thanks in advance,
    Jaxon


  • #2
    Re: can you convert a carburated motor to EFI?

    No big deal to convert a carbed 350 to EFI. Block is the same, its all just bolt on pieces. Won't be cheap.

    What do you think you'll gain with the EFI over a properly running carbed motor? You won't see any gains in power because of the EFI.

    8000 pounds is a heavy boat for a small block. Only way you'll make a 25% to 30% gain in cruise speed is with significantly more power.
    Any opinions expressed above are worth exactly what you paid for them!

    Comment



    • #3
      Re: can you convert a carburated motor to EFI?

      Well more power is the only way to go........ you could stay on the 350 platform and install a 383 Stroker........

      The other scenario is maybe re-prop the boat. If the 350 is hitting proper rpms you might be able to go up in pitch a hair.
      This is a great link to boat specifications http://boatspecs.iboats.com/
      Please, shop iboats first!!

      Comment



      • #4
        Re: can you convert a carburated motor to EFI?

        Originally posted by 45Auto View Post
        No big deal to convert a carbed 350 to EFI. Block is the same, its all just bolt on pieces. Won't be cheap.

        What do you think you'll gain with the EFI over a properly running carbed motor? You won't see any gains in power because of the EFI.

        8000 pounds is a heavy boat for a small block. Only way you'll make a 25% to 30% gain in cruise speed is with significantly more power.
        I guess I was under the impression that in a marine application a stock EFI 350 are generally about 50 horse more than the carburated ones and run more efficeiently. I don't know exactly why that is, whether they have more compression, higher performance heads, intakes, etc. or just a combination of these things? It's true that the crusader motor that's in my boat does post about 270 horse stock which is higher than a run of the mill marine 350 and since it was rebuilt and bored over I'm sure it's in the neighborhood of 300 horse but nothing real crazy. Am I all wet on this idea?

        Comment



        • #5
          Re: can you convert a carburated motor to EFI?

          Originally posted by Bob_VT View Post
          Well more power is the only way to go........ you could stay on the 350 platform and install a 383 Stroker........

          The other scenario is maybe re-prop the boat. If the 350 is hitting proper rpms you might be able to go up in pitch a hair.
          I did re-prop the boat and run two different props. I use one up here in Idaho on the lakes, and another down on the coast on the salt. It will run about 4000-4200 wot, which I think is about right. As far as stroking the motor goes, It's something that I've always wanted to do, but never have. I'm sure there is alot more involved in doing so, and I don't think you would want to stroke a used motor, would you? If I was going to stroke the motor, is there a basic formula that you would use in doing so, meaning heads compression, etc. I know there are all kinds of different configurations, where would you start and what kind of gains can I expect? What about efficiency and reliability, is that compromised.

          Comment



          • #6
            Re: can you convert a carburated motor to EFI?

            Is it a 2 or 4 barrel carb.
            I've got a full roller 350 out of a zz4 camaro that put down 335 horsepower with a 2 barrel put a 4 barrel just for dyno purposes and went up to 360. went back to the 2 barrel for economy but if I
            needed the power it is nice to know what I would get with a 4 barrel. with the 2 barrel I am pushing my 7200# 32 mph at 5000rpms. I cruise most of the time at around 26mph at 3000rpms.
            Fuel injection will make more power and economy will be better. Why is EFI better then a finely
            tuned carb. Fuel atomization is better, With higher fuel pressures and injectors causing fine
            atomizing of the fuel instead of carbs producing droplets the power is increased as well as the
            economy. Another benefit to EFI is quicker cold starts and no need for chokes.

            Comment



            • #7
              Re: can you convert a carburated motor to EFI?

              Holley makes a Marine Pro-jection unit that bolts on to the manifold where the carb was. it is a TBI setup, however you would be a step above the carb with fuel management
              1988 Cruisers Rogue 2420 - VP AQ271C / 290DP "Rock'n Along"
              http://forums.iboats.com/showthread.php?t=500145
              1970 Wooster Hellion 7' of cool mini boat with a Merc 9.8
              Recent Boats
              2002 SeaRay 190BR - MC 5.0 / Alpha I series II "Cheasheads in Paradise"
              1984 Avanti 170DLI - OMC 3.0 / OMC Stringer 400 "Ship Happens"

              The problems we face today can not be addressed at the same level of intelligence we were at when we created them - Albert Einstein Or with the same level of $ - Me

              Comment



              • #8
                Re: can you convert a carburated motor to EFI?

                Originally posted by snake77 View Post
                Is it a 2 or 4 barrel carb.
                I've got a full roller 350 out of a zz4 camaro that put down 335 horsepower with a 2 barrel put a 4 barrel just for dyno purposes and went up to 360. went back to the 2 barrel for economy but if I
                needed the power it is nice to know what I would get with a 4 barrel. with the 2 barrel I am pushing my 7200# 32 mph at 5000rpms. I cruise most of the time at around 26mph at 3000rpms.
                Fuel injection will make more power and economy will be better. Why is EFI better then a finely
                tuned carb. Fuel atomization is better, With higher fuel pressures and injectors causing fine
                atomizing of the fuel instead of carbs producing droplets the power is increased as well as the
                economy. Another benefit to EFI is quicker cold starts and no need for chokes.

                I wonder how much performance would be increased by making a non-roller a roller motor and what the cost would be. If I found an EFI motor out of a car what changes would have to be made to make it a marine motor. I know that a marine application puts the motor under load the whole time. Can you just swap out a car motor and then hang your marine alternator, etc. or is it more involved?

                Comment



                • #9
                  Re: can you convert a carburated motor to EFI?

                  Why is EFI better then a finely tuned carb. Fuel atomization is better, With higher fuel pressures and injectors causing fine atomizing of the fuel instead of carbs producing droplets the power is increased as well as the economy. Another benefit to EFI is quicker cold starts and no need for chokes.
                  What you say is true. Instead of 260 HP with his carb, he'll have 261 HP with the fuel injection. Instead of 2 MPG with the carb, he'll get 2.01 MPG with the fuel injection. Neither is going to make a significant enough difference for him to notice.

                  It is definitely much easier to start a fuel injected motor. Just turn the key. If he's incapable of figuring out how to pump the throttle a few times before the first cold start of the day as required with a carb, fuel injection may be a huge benefit.
                  Any opinions expressed above are worth exactly what you paid for them!

                  Comment



                  • #10
                    Re: can you convert a carburated motor to EFI?

                    As stated by others, I see fuel injection as a way to get easier starting, and better economy, not so much more performance. Boats can be touchy, where adding a good amount of power, only nets a knot or two. Sure it's better, but the expense may not be worth the slight gains. I have thought about taking my carbed Crusaders and going FI, but for the time being the carbs are working perfectly fine.

                    I will say, your performance numbers look pretty good for a 28' 8000 lb boat with a single small block. Mine is just slightly faster, but has twin 270 Crusaders.
                    Boat: 1987 29' Cruisers Inc 297 Elegante. T/270 Crusaders. (SOLD)
                    Boat #2: 1984 34' Silverton 34C. T/270 Crusaders. Westerbeke Gen.
                    Updating Thread: http://forums.iboats.com/boat-restor...vy-534493.html
                    Race Car: 1989 Mustang LX 5.0. 12.5 on slicks, 12.9 on street tires.
                    sigpic

                    Comment



                    • #11
                      Re: can you convert a carburated motor to EFI?

                      Repeat after me class - there's no replacement, for displacement!

                      Others have said it, strictly a swap to EFI won't do it. You need to add other hop-ups to get the power out of the motor. Need to weigh the cost of those vs the cost of going to a big block.
                      Jon Hunter
                      Marion, NY

                      2006 Procraft 200 Combo with Merc 200 Opti
                      2007 Homemade Duck Boat with Merc 39

                      Comment



                      • #12
                        Re: can you convert a carburated motor to EFI?

                        Originally posted by Captain Jaxon View Post
                        I did re-prop the boat and run two different props. I use one up here in Idaho on the lakes, and another down on the coast on the salt. It will run about 4000-4200 wot, which I think is about right. As far as stroking the motor goes, It's something that I've always wanted to do, but never have. I'm sure there is alot more involved in doing so, and I don't think you would want to stroke a used motor, would you? If I was going to stroke the motor, is there a basic formula that you would use in doing so, meaning heads compression, etc. I know there are all kinds of different configurations, where would you start and what kind of gains can I expect? What about efficiency and reliability, is that compromised.
                        You might be over propped you're WOT on a 5.7L should be about 4500 rpm
                        There is no unhappiness like the misery of sighting land (and work) again after a cheerful, careless voyage. Mark Twain
                        T
                        “The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.” ~William Arthur Ward

                        Never argue with a fool, people might not know the difference.

                        Comment



                        • #13
                          Re: can you convert a carburated motor to EFI?

                          Supercharge it? A little boost goes a long way.
                          1987 Skeeter 175 Starfire with a Yamaha 150 ProV

                          Comment



                          • #14
                            Re: can you convert a carburated motor to EFI?

                            Originally posted by Angrywasp View Post
                            Supercharge it? A little boost goes a long way.
                            Towards pre-detonation and other quick ways to have to rebuild an engine if not done properly.
                            1975 Wellcraft Airslot 165 - 94 Johnson 120hp VRO

                            Comment



                            • #15
                              Sign up today
                              Re: can you convert a carburated motor to EFI?

                              Originally posted by Captain Jaxon View Post
                              I wonder how much performance would be increased by making a non-roller a roller motor and what the cost would be. If I found an EFI motor out of a car what changes would have to be made to make it a marine motor. I know that a marine application puts the motor under load the whole time. Can you just swap out a car motor and then hang your marine alternator, etc. or is it more involved?
                              Depends on the water you're running in. I'm no expert, but as I understand it, you need special marine head gaskets if you're going to run in salt water, a different cam for a marine application, and all of the marinized components attached to the engine, such as alternator, starter, distributor.
                              I would suggest turbo charging, but like super charging, the bottom end of your engine needs to be built to handle the higher cylinder pressures, and with a turbo I imagine you have to have a special marine turbo that has a water jacket around the exhaust housing.
                              You may find it cheaper to repower with a big block.

                              Chris
                              1996 Rinker Flotilla, 4.3, 1998 Seadoo GSX Limited, 1995 Hydra 24' Pontoon, 70hp Force, 1995 16' Alumacraft Jon boat, 25hp 'Rude, 1968 Fibra with Volvo stern drive, and various other boats used for parts.

                              Comment


                              Working...
                              X