Replacing Volvo Penta 5.7 GSI with a New Carburetor version OR Fuel Injected version

[James Adelman]

I have a Chaparral Signature 260 with a 5.7 GSI Volvo Penta that needs a ECM but unfortunately they are not available any longer. Choice is to remove the Throttle Body Fuel Injection and go to a Carburetor. Second Option is to replace the entire engine (tired of fixing things every two months. If I go that route I am looking for feedback on whether to go with a Carburetor Version to avoid all the Emission related issues with the new Fuel Injected versions. Need some feedback please.

 

[Saline Marina]

In vast generalities, I would take a look at an automotive ECM to first see if it has the same connectors. a fullsize 1500 GM truck from 88-93 would probably do it with. Driving at the probability that VP didn't invent their own ECM for marine use. They probably copied the GM version, turned off the O2 sensor feedback, and made the circuit board more robust with a coating for the moist environment.

E.G. If I took my TBI truck engine and unplugged the O2 sensor(s) it would set a code and still run just fine...without the long term fuel trim.

I don't want to convince you its a rock solid solution but something to consider researching. Also knowing you're jumping outside the SAE J1171 ratings but when the parts are NOLA then some creativity is in order.

The 5.7/350cid can easily run a marine carb with a low-pressure fuel pump (not sure how the TBI is setup, I think 2 fuel pumps - but I can't say if the low pressure can go straight to carb or how the filter is integrated). Not sure of your ignition system but the small-cap remote-coil HEI distributor (its round more or less and not the spidery flat distributor) running on ignition module alone and without knock sensing would be just like a 5.7GL. You'd have to go with a conservative base time like 0deg BTDC and monitor closely for knock when running hard. There's always the route to run 89 or 91 premium if knock develops but this fuel is of course more expensive.

 

[Bondo]

Choice is to remove the Throttle Body Fuel Injection and go to a Carburetor.

Ayuh,...... Welcome Aboard,....... It shouldn't be to hard to find a 4.bbl carb, 'n cast iron, or a marine aluminum intake,.....

Dependin' on the ignition, it might run alone, without the dead 'puter,.... Donno, yer motor,.....

Like SM says, ya need low pressure fuel delivery for a carb, so the stuff there now is surplus,....

 

[Lou C]

I'd be leaning toward the carb just for reasons of cost and lack of dependence on OEM parts that can become NLA as you found out, Volvo used a Holley 4175 spread bore 4bbl on these...and the only other unknown as Bondo said was the ignition system, however, that will require a bit of research to see how the original Volvo system was set up...if it integrated a knock sensor then yes it might need an ECU to work, but if not then it might not. As far as intake manifolds it depends on what version of hte 5.7 you have...Pre-Vortec, or Vortec… the pre Vortecs have 12 bolts holding down the intake,,,,the Vortecs have only 8...you'd also need a low pressure electric pump unless your engine is old enough that it could have come with a mechanical pump (look for a block off plate on the lower front starboard corner of the block...if nothing is there then you need a low pressure marine electric pump wired through the oil pressure sending unit as a safety....

 

[alldodge]

Good grief, do not look for a truck ECM to replace yours with, other then after talking to OBD and see if it can be reflashed

You may be able to have yours repaired, reflashed or replaced with another one by contacting OBD Diagnostics. Call Bob and ask before you proceed


https://obd2allinone.com/


So far as switching to carb, that is easy enough but requires some parts changing

 

[cptbill]

^^^^ What he said. You should be able to locate at least a used ECM. If you fell like repowering my advise would be to move forward not backwards fuel injected engines out preform carbed motors 95% of the time and the fuel efficiency is much better

 

[Lou C]

Ahh well I say for a recreational boater if the part you need for the efi is NLA, a carb will outperform that 100% of the time because it works; can be repaired or replaced easily. A system made obsolete by a manufacturer’s capricious cost cutting is useless to the recreational boater. You can go and buy a low pressure electric fuel pump, GM marine or aftermarket intake and a brand new Holley or Edelbrock 4 bbl carb, that will give you 90% of what EFI gives you, when it works right now it’s giving the o.p. zero.

 

[Saline Marina]

Edelbrock has a new-er carb called AVS2 which has 8 outlets on each main jet instead of 1, to help improve atomization issues which plague low airflow operations in a carb, where TBI and SFI fuel injection systems do better. I have not tried it on a truck app but I'm very interested in it. The one concern I have is the super small passages might be a problem area when it comes to fuel gumming issues. However on that carb the jet's outlet is a part that's easily removed from the top without removing the carb itself. The main concern would be dropping screws down the throat (!) I'm also not sure if a marine version of that carb exists yet.

It does seem like the ECM should be able to be repaired somehow. I am curious about the fail mode...is there a code set or does the engine just stop running?

The ECM's job is relatively simple in TBI, its inputs are things like MAP, TPS, the coil pulse from the ignition module, the coolant temp sensor, potentially knock sensor(s) and its outputs are the timed injector pulsewidth and modifications to retard spark thru the ignition module if knock is sensed. In marine apps, the EGR is turned off and the O2 feedback is turned off.

An important thing to recognize is that the ignition module is standalone as far as getting the magnetic impulse for cam reference and firing the coil to produce the spark. The advance curve is built into the ignition module. However the ignition module has an analog input tied to ECM output that is a reference to determine the amount of spark retard from what would be normal advance, and that's just in the case of knock sensing.

 

[Lou C]

Yes ECMs can be repaired...I had this done when the electronic control on our 26 year old gas range started beeping with false alarms...I found a place out in Kansas that repairs ECUs for appliances and it worked great. Cost about $150 to get the ECU repaired and has worked great over a year. We had an engine ECU replaced on our '98 Jeep about 7 years ago and I think it is a Mopar reman unit, there are aftermarket places that re-do them as well. The Mopar re-man installed and programmed was approx. $600.

I was looking at a Merc parts diagram the other day and happened to notice they mount the ECU on some models...of all places...on the exhaust elbow! One good overheat and its toast! I'll take my old back yard engineering, rebuilding carbs in my garage, points distributors...etc...over...these...."improvements" and "progress" anyday!

 

[QBhoy]

Hi
You can get it sent away and repaired. The ecu. Loads do it.
I’m amazed you can’t get another ecu. The merc efi same cc engine will be the same unit too, if it helps.