can you convert a carburated motor to EFI?

[Captain Jaxon]

Re: can you convert a carburated motor to EFI?

To op, you will NOT see any HP increase by just adding TBI system. Fuel injection was developed for the purpose of economy and cleaner pollution not HP gains. FI when properly done it will cost more than a used big block. You have to not only have to change over the carb but the whole fuel delivery and return system, electronic engine control module and proper tuning etc,etc. MPI (multi port injection is even more involved as it will require swapping manifolds, timing components etc, etc. Turbocharging will most likely melt your boat from within but a supercharger will double the horsepower output for every 14.7 pounds of boost, on a used motor that is a big gamble since there will be no asphalt for the pistons to bounce off of when she lets go. Beside adding boost will definitely increase your fuel consumption. As others said changing the motor is best way to gain performance. A merc 5.0MPI will put out 260 HP and same VP will do 270 prop horsepower, no solution will be cheep. For the special occasions where you need to impress someone just get NOS installed, that will be like getting extra 150 HP at a push of a button - this last one was a joke and please don't add explosive gas to your boat.

Yeah I don't want to get silly about this. Reliabilty is a huge part of my decision making process. If I wanted to build a real high output motor I don't think this is the boat for it. Great advice, thank you.

 

[Captain Jaxon]

Re: can you convert a carburated motor to EFI?

while an EFI motor does have a higher output than carbed version of the same engine (Example - Mercruiser 5.0 liter 220hp carbed, 260hp MPI). the output is based on the ability to properly manage fuel and spark while balancing on the edge of detonation vs. relying on a glorified toilet float (carburetor) and a simple distributor.

Can you change to EFI - yes. can you to it cheaply - depends. is it worth it - dont know (you have to answer)

depending on the rebuild that you did (stock refresh, new lower, etc?), here is what I would suggest:
switching to Vortec heads. if you have closed cooling, then switch to a set of aluminum AFR heads.

Change cam - suggest looking to go with a comp cam - either the CL12-236-3 or the CL12-232-3 there are more radical cams, however I wouldnt suggest them without knowing more about your drive, which company did the marinization, etc.

The head change will require a manifold change (go aluminum if you have a closed cooling system). Also look at the carb - is it big enough?

Careful shopping gets you everything in the $1500 range (unless you buy the AFR heads) and about 300-320 hp (depending on cam, tune, elevation, fuel, etc.)

if that is not enough and you want to stay with a small block, then build a 383 and get 350-420hp, or build a blower motor out of a 350 or 383 for 400-550hp. Then again if you intend to go that route for the same money, I would simply spring for the LSA marine engine at 425hp. you get aluminum engine, supercharger, EFI all in one package.

speed costs money. I would also look at how much you want to spend to take your cruiser faster vs how many margaritas I could buy while pulling a pair of jet skis with me

This is some really useful information, thank you. I've got some thinking to do. One big reason for wanting to get the boats cruise speed up, is that the bow really sits down about 25 mph, and rides really nice and flat. As it is now the bow rides pretty high and vision isn't the best. I've played around with moving some weight up front and it definitely helps. I don't use the boat much for cruising, we really enjoy our trips to Canada ocean fishing. The guys I go with have smaller boats and it seems like I spend a lot of time steaming while they're fishing. Of course there are lots of trade offs and when the weather is nasty I do have an advantage, that's why I bought the boat. I guess the real question is, if 50 or so horse power would gain my speed issue. I still haven't gotten a clear idea on what differences auto motors and marine motors have? I thank you all for the responses, this is a useful resource. Can anyone give me help on trying to identify the kind of heads I have on my 270 crusader. I can't help but think she is running a little better than stock?

 

[Captain Jaxon]

Re: can you convert a carburated motor to EFI?

To answer your question, "can you convert a carburated motor to EFI?", yes you can, I've done it.
Will it do what you want it to do? In your case, I doubt it. It sounds to me like you have a healthy engine and it's doing very well to move your boat at those speeds. Other than making sure that is in a very fine state of tune, and after that, if you still want more speed, I'd side with the camp that suggests re-powering with a big block for a reliable power increase.
Electronic engine management in general, and programmable electronic engine management in particular, just does the same thing as a conventional carburetor and ignition system except that it allows you a much finer degree of control. A well tuned carb and ignition system does a good job of delivering the right fuel mix and ignition timing, particularly in the upper speed and load ranges. EFI can improve on this a bit, but not much. Where EFI can make the most gains is in the lower load, lower RPM ranges. There are significant economy gains to be made here, but if I understand your post correctly, this is not the area you are looking to improve.
Hope this helps.

If I did go to a big block would weight difference cancel out potential gains? Which motor would you go with? Thanks
Jaxon

 

[E4ODnut]

Re: can you convert a carburated motor to EFI?

I'm not familiar with your boat, but you say it has a velvet drive transmission, so I assume that it is shaft drive. If the boat's attitude is an issue, would trim tabs be of some help?

As for choice of engines is concerned, there really are no bad ones, so a major consideration would be cost and availability of the marine specific parts. The 454 GM engines have been around in marine form for some time. Parts are relatively cheap and readily available. Others may be able to advise you better than I can in this regard.

 

[Scott Danforth]

Re: can you convert a carburated motor to EFI?

This is some really useful information, thank you. I've got some thinking to do. One big reason for wanting to get the boats cruise speed up, is that the bow really sits down about 25 mph, and rides really nice and flat. As it is now the bow rides pretty high and vision isn't the best. I've played around with moving some weight up front and it definitely helps. I don't use the boat much for cruising, we really enjoy our trips to Canada ocean fishing. The guys I go with have smaller boats and it seems like I spend a lot of time steaming while they're fishing. Of course there are lots of trade offs and when the weather is nasty I do have an advantage, that's why I bought the boat. I guess the real question is, if 50 or so horse power would gain my speed issue. I still haven't gotten a clear idea on what differences auto motors and marine motors have? I thank you all for the responses, this is a useful resource. Can anyone give me help on trying to identify the kind of heads I have on my 270 crusader. I can't help but think she is running a little better than stock?

both Automotive and Marine motors come from the same parts bin. Now the difference - Marine motors have brass freeze plugs vs plated steel, and different head gaskets and head spacers to handle salt water. the cam for marine is to provide a nice flat torque curve vs automotive which is more peaky. Marine electrics are non-sparking and must be to prevent explosions in the bilge. Fuel systems are slightly different for the marine environment, and the spark management is slightly different.

you have a 270 crusader which is a basic small block marinized by crusader (now pleasurecraft) and based on a 1978 industrial engine which is a truck engine with a different cam, so switching to vortec heads (new pair about $600) would help over your basic late 70's castings. if you did nothing but refresh it and not jump into the meat of the engine, cam, or fuel system, you have about 270hp the engine came with.

do you have a closed cooling system? if so, then you can run aluminum engine parts such as heads, and intake and lighten up the engine by 80#

you will have to verify with the v-drive the maximum power you can put thru it regardless of big block vs small block. over the years there have been 4 itterations of small blocks and 4 itterations of big blocks in the non-performance marine world. add to the mix the new LS based engines, diesels, etc. and the mix gets heady quickly.

would an extra 50 help - probably

the fact that your front end is pointing skyward indicates that you have an issue there as well. your boat should plane out flat. trim tabs will help here.

 

[bnicov]

Re: can you convert a carburated motor to EFI?

No substitue for cubic inches!! Look at either a 454 or 496 if you want a real difference in speed. Your limiting factor is the outdrive. What can it handle??

 

[QC]

Re: can you convert a carburated motor to EFI?

Your limiting factor is the outdrive. What can it handle??

It's an inboard . . . Still a factor, which model Velvet drive?

 

[Captain Jaxon]

Re: can you convert a carburated motor to EFI?

both Automotive and Marine motors come from the same parts bin. Now the difference - Marine motors have brass freeze plugs vs plated steel, and different head gaskets and head spacers to handle salt water. the cam for marine is to provide a nice flat torque curve vs automotive which is more peaky. Marine electrics are non-sparking and must be to prevent explosions in the bilge. Fuel systems are slightly different for the marine environment, and the spark management is slightly different.

you have a 270 crusader which is a basic small block marinized by crusader (now pleasurecraft) and based on a 1978 industrial engine which is a truck engine with a different cam, so switching to vortec heads (new pair about $600) would help over your basic late 70's castings. if you did nothing but refresh it and not jump into the meat of the engine, cam, or fuel system, you have about 270hp the engine came with.

do you have a closed cooling system? if so, then you can run aluminum engine parts such as heads, and intake and lighten up the engine by 80#

you will have to verify with the v-drive the maximum power you can put thru it regardless of big block vs small block. over the years there have been 4 itterations of small blocks and 4 itterations of big blocks in the non-performance marine world. add to the mix the new LS based engines, diesels, etc. and the mix gets heady quickly.

would an extra 50 help - probably

the fact that your front end is pointing skyward indicates that you have an issue there as well. your boat should plane out flat. trim tabs will help here.

Danforth,
Man oh man that's some good info, thanks. I do have trim tabs, in fact big ones. I can push the front down with them, but The thing that I hate is inevitably, you are running one side more than the other and when you hit some rollers sideways it can really make the boat list like from side to side. It lists enough sometimes to make you pucker. I don't want to make it sound like it's pointing straight up, because it's not. It just seems like the boat feels right at that 25 mph range. It seems like the motor is working a liitle more than it should at 18-20 at not so muchat the 25 mph, but my rpm's are about 3500 which I think is a little high. It does have a closed loop cooling system, it runs about 160 degrees. Also, yes it is a velvet drive with an 1 1\4" shaft with an 18, 18 brass prop. I don't know what kind of h.p. the v-drive is capable of handling, but that shouldn't be too hard to figure out. Aluminum heads sure sound like a possibility, what kind of gains do you think I could get with putting heads on it. Also, it has a thru-hull exhaust, but it goes from a collection chamber and out a single 3" tube. I wonder if upgrading to two 3" tubes would let it breath a little better?

 

[Captain Jaxon]

Re: can you convert a carburated motor to EFI?

No substitue for cubic inches!! Look at either a 454 or 496 if you want a real difference in speed. Your limiting factor is the outdrive. What can it handle??

I don't know, but I am going to check that out, thanks.

 

[Captain Jaxon]

Re: can you convert a carburated motor to EFI?

It's an inboard . . . Still a factor, which model Velvet drive?

I'll post the answer tomorrow.

 

[Scott Danforth]

Re: can you convert a carburated motor to EFI?

look up your V-drive model number for maximum torque and RPM you can put thru it without blowing things up. if you need more power that will be the limit or your looking at a new drive as well. and if you do look at a new drive, I would personally go diesel at that point but that is me.

Aluminum heads are much lighter than the cast iron counter parts and that is the main benefit. however with AFR heads (about $1500 a pair) and ceramic coating the combustion chambers (about $500) you can get about 400-420 hp in a marine application and 500hp in a street application with a carburetor and on pump gas.

the AFR aluminum heads over a standard iron vortec are good for about 30hp at 5000 rpm (more at higher RPM's). however that comes at a premium price as compared to iron heads.

keep in mind, any performance mod done to a small block can also be done to a big block.

160 sounds low for a closed cooled system I recall 180 being for closed cooled and 160 being for open cooled engines, however I have been wrong before.

 

[QC]

Re: can you convert a carburated motor to EFI?

look up your V-drive model number

Just for clarity I assumed this boat was a direct drive. Can you confirm Jaxon?

Also, still need to address reversion if we are talking marine performance mods

 

[Captain Jaxon]

Re: can you convert a carburated motor to EFI?

Yes it is a V-Drive. I can't seem to find my serial number on the sites that I looked at. I can probably call someone with my serial number tomorrow. I didn't look until later in the evening. In case anyone might know, here are the numbers.
It's a Borg Warner Velvet Drive
Product # 1004-000002
Ratio: 2.0
Serial # 2509

 

[Scott Danforth]

Re: can you convert a carburated motor to EFI?

I did a quick search and can not find the torque limitations. however you are limited to 5200 RPM max from what I could find. someone on here will have the max torque input to the drive

 

[John_S]

Re: can you convert a carburated motor to EFI?

Performance wise, EFI is about equal to 4brl carb. MPI can squeze a little more hp out of it. But, as numerous others of said, you need displacement. You need pure grunt power, not high rpm band hp, so 383 or BB.

If adding any heads to your 70's vintage small block, you will need to know what pistons are in it. Typically, they were flat-top then. Adding vortecs (64cc), will give you higher compression than what you want in a big heavy boat. You might get by with it on a light runabout.

 

[stackz]

Re: can you convert a carburated motor to EFI?

grab a tuned port intake setup from a camaro/corvette off ebay, grab a marine HEI (thunderbolt IV) distributor off ebay.

get a megasquirt 2.0/3.0 system and buy the VE autotune software. wire it up, load the software on your laptop and hook it to the megasquirt.

fire it up and let it tune the ecu by itself.

then toss on a vortec system and retune for that.

enjoy.

*note* some customization will be required

 

[Volphin]

Re: can you convert a carburated motor to EFI?

If you are building the motor, or plan to, go with Vortec iron heads. You can make more power out of them than AL heads. Use a nice dual plane aftermarket intake and a bolt and go supercharger with 5-8 lbs of boost. Stock bottom ends do not like 10psi + of boost, but you are safe at 8, especially at the lower operating temps of marine apps with raw water. PM me if you need more info on the heads or have any Qs. It's bolt and go HP.

V

 

[Captain Jaxon]

Re: can you convert a carburated motor to EFI?

Scott,
Ok thanks. Sorry I have written back. I still haven't found out what kind of hp I can put in front of the v-drive. If anyone knows I'd appreciate the info. It's kind of looking like big block. Do you or anyone know, roughly the weight difference? How much hp gain can I expect in a stock application big block? Wasn't the dodge 440 a commonly used marine motor?

 

[Captain Jaxon]

Re: can you convert a carburated motor to EFI?

Performance wise, EFI is about equal to 4brl carb. MPI can squeze a little more hp out of it. But, as numerous others of said, you need displacement. You need pure grunt power, not high rpm band hp, so 383 or BB.

If adding any heads to your 70's vintage small block, you will need to know what pistons are in it. Typically, they were flat-top then. Adding vortecs (64cc), will give you higher compression than what you want in a big heavy boat. You might get by with it on a light runabout.

Imported John,
Call me stupid, but why is higher compression on a big boat a bad thing? I am leaning toward the big block now, but I thought getting 50 reliable hp out of my motor wouldn't be too big a deal and it would be problem solved. I'm still open to suggestions and I have had a lot, but I'm not ready to say "that's the one," yet.

 

[Captain Jaxon]

Re: can you convert a carburated motor to EFI?

grab a tuned port intake setup from a camaro/corvette off ebay, grab a marine HEI (thunderbolt IV) distributor off ebay.

get a megasquirt 2.0/3.0 system and buy the VE autotune software. wire it up, load the software on your laptop and hook it to the megasquirt.

fire it up and let it tune the ecu by itself.

then toss on a vortec system and retune for that.

enjoy.

*note* some customization will be required

That doesn't sound too hard, but what will that get me. Hopefully more efficient hp.