mercruiser 350 magnum efi, possible propane conversion.

[saltwater_cowboy]

Hi Guys,<br /><br />I'm here in the UK where we are currently paying over $8 a gallon on gas.<br /><br />I have been running cars and boats on propane for a while as its less than have the price of gas.<br /><br />On my last boat (which I just sold) I had an impco propane carb sat upon holley throttle plates. Boat was a mastercraft with indmar 351.<br /><br />I'm currently looking at a 96 maxum with the 350 magnum efi engine. Can anyone familiar with the engine tell me if I'd need to change the intake manifold to repace the fuel injection with something like a quadrajet thottle plate that I could then mount a impco propane carb to.<br /><br />Other option for me would be to find a propane mixer that will fit the air intake and possibly run the boat dual fuel, switching between propane and gas as need be. My car has a system like that.<br /><br />Anyone know if the brain for the efi is connected with the ignition? On my car I simply have a relay that powers off the efi brain when I'm on propane but I know with some cars this also powers down the ignition. To get round it you can sit an emulator to the injectors to make the brain think they are still sqirting gas.<br /><br />Anyone care to comment or am I just rambling now?

 

[Haut Medoc]

Re: mercruiser 350 magnum efi, possible propane conversion.

Jay, I have heard much about alternitive fuel sources.....But not propane....The price of petrol is fearful....Any info you an give to the Colonies will be appreciated.....I think it that it is time for us to get with the times....I can't help you but would love to see this thread come to some sort of fruition....FORUM? Cheers,Jay....JK

 

[saltwater_cowboy]

Re: mercruiser 350 magnum efi, possible propane conversion.

Well propane as a fuel is extremely popular in Europe. Its avery clean fuel, good for the enviroment and engine run very smoothly on it.<br /><br />I only really have knowledge on propane carbs bolted to either holley or quadrajet thottle plates as I have had 2 boats with this set up.<br /><br />Converting a boat with efi is new to me but shouldn't be much more tricky than my own car.<br /><br />Don't know what propane prices are like for you in the states but I guess cheaper than petrol?

 

[Dunaruna]

Re: mercruiser 350 magnum efi, possible propane conversion.

These days, the most common way to run dual fuel on an EFI is to interface with the ECU. The LPG (propane) kit has a stepper motor and ECU included which 'talk' to the original ECU.<br /><br />The vapor line is simply plumbed into the air intake tube just before the throttle body.<br /><br />There are many dangers with using LPG in a boat. Like gasoline vapor, leaking LPG will collect in the bilge, but it won't evaporate and it will expand - big badaboom!!!!<br /><br />Not recommended.<br /><br />Aldo

 

[saltwater_cowboy]

Re: mercruiser 350 magnum efi, possible propane conversion.

I know many people here in the UK that have run their boats on propane for 10+ years without any issues.<br /><br />Many UK boat dealers will factory convert your boat from new.<br /><br />Propane is no more dangerous in a boat than gasoline. Correctly vented bilge, spark arrested components, blower and a vapour alarm will keep you safe.<br /><br />Propane also has more safety items built in like pressure relief on the tanks and safety cut outs and fuel shut off solenoids. In my opinion and thats 10+ years of using my mastercraft with propane its safer, cleaner and better for the engine.<br /><br />Also the most common way to run dual fuel in europe is not to have a system that talks to the ecu, its to have a system with its own ecu that takes its input from the lambda sensor on the exhaust and then uses this info to rich/lean the fuel via a stepper motor. This system is called closed loop. This then works in real time and adjusts mixture as nessacery. There is then a box that connects to the vehicles ecu and injectors and fools them into thinking they are working normally by emulating the signals they are expecting to recieve.<br /><br />On a boat there is no way to install an lambda sensor as as such the system would then be described as open loop (no feedback to control mixture).<br /><br />Other options include a propane injection system which has an injector for each cylinder placed into the inlet manifold and this has an ecu which takes its signals from the original vehicles ecu and injects propane as required. <br /><br />I think I'll wait until I have got the boat and then work out whats the best way to install a system. I'd prefer a straight propane system and for this I guess I'd need to replace the inlet manifold with one capable of taking a spreadbore or holley type carb and then mount a propane carb to that hoping the ignition system will work ok with the injection ecu disabled.

 

[Dunaruna]

Re: mercruiser 350 magnum efi, possible propane conversion.

In a car, the oxygen sensor & the TPS send readings to the original ECU. The LPG ECU needs the oxy sensor (and the TPS) to adjust the stepper motor. It doesn't guess, it needs the data from these two items.<br /><br />Also, at startup, the LPG ECU times out (it shuts down). The vehicle automatically starts on petrol, even if the switch is on 'LPG'. The LPG ECU is programmable to automatically switch over to LPG at a given RPM at acell or decell. How does it know what the RPM is? (retorical)<br /><br />The two computers 'talk'. Or would you prefer the word 'interface'?

 

[Limeyguy]

Re: mercruiser 350 magnum efi, possible propane conversion.

Jay - I was thinking about an LPG conversion too then I found out Calor had recently closed down most of the UK marina refilling stations (due to not selling enough to make worthwhile). Very difficult to get hold of the stuff now which is a shame at less than half the cost of petrol.<br /><br />Of course, if you're on a trailer there's no problem u can use car filling stations.

 

[rodbolt]

Re: mercruiser 350 magnum efi, possible propane conversion.

proplem here is most folks aint got sense enough to use gasoline much less LPG or CNG. that and our coast guard says no bottled gas in an enclosed engine bay. but with fuel costs rising they may have another look at it.<br /> but so far here the price of LPG has kept up with the price of gasoline and heating oil.