Merc 4.3 MPI vs carb

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wengr

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Hello. I am in the market for a bowrider, 18 - 20 feet, and I believe I would prefer the merc 4.3. Family use/watersports on local lakes only. I am looking for well maintained excellent condition examples, and it seems that budget will only provide for about a 10 or 12 year old boat.
My question is: Should I prefer a Merc 4.3MPI, or carb version? In my experience with motorcycles and powersports, I would opt for EFI every time, but I appreciate that this is not a motorcycle. I would have expected that, while hard to find, mpi would be much less likely to be a pia, but many of the problem threads on here have me now questioning that.
Also, to what degree is the additional power from mpi version likely to be a factor for skiing in a br of 20ft or less?
Any info appreciated.
 

tpenfield

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:welcome:

Yes, it has been a rough couple of months for those MPI/EFI engines, based on recent threads. MPI engines are great up until the point where they have a problem, then they become a nightmare. Carb'd engines may not be as sophisticated, but when they are having issues, usually you can sort it out fairly quickly with the toolset you got on your birthday..

I would not be overly concerned about a slight power difference between the two types of engines. If power becomes a concern, then maybe opt for the 5.0 in your search.
 

Scott Danforth

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I would go with a 5.0 or 5.7 myself over the 4.3. Carb is fine vs MPI. as Ted stated, MPI works great until it doesnt. a carb can be diagnosed and fixed with a swiss army knife and a flashlight.
 

jimmbo

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MPI is great while it works, when it acts up, nothing but headaches. Have had a carbed 5.7 VP on an 18 1/2 foot for 15 yrs, wouldn't trade it for a FI for all the tea in china.
 

Scott06

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Agreed on the MPI comments, i think we all agree that mpi is better technology for sure. I think it depends on your mechanical aptitude and how much you enjoy working on the boat. I chose a carb when I repowered because I know I can fix it, but I know that I probably have a carb cleaning and rebuild or two in my future.
 

thumpar

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I like the EFI route. For me it seems easier to work on but I am also an IT guy to is makes sense. The problem may be finding a 4.3l MPI in a boat that fits what you are looking for. I don't see the 4.3l MPI equipment come up for sale to often. You may consider looking for 5.7l EFI. They are a simpler than the MPI but still fuel injected.
 

thumpar

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It just makes it easier for me to understand then a carb. I get that input signals go in to come up with the way the injectors fire and spark plugs fire to make it run. I also get how carbs work but never good at diaging past rebuild it when it runs bad. I don't know a thing about jetting or setting float other then do what the spec says. To me a computer controlling it is simpler where some a carb is easier.
 

bruceb58

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Carbs are a hundred times simpler than FI and I came from working with engine control modules when I worked as an electrical engineer for GM!

I am guessing you own a Rinda or similar tool when troubleshooting your FI? Same goes for when you troubleshot the FI in your car?
 

Scott Danforth

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If you can fix a toilet, you can fix a carb. The theory and operation is the same
 

Dave-R

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Must be the old dogs and new tricks choice for me also . I have a 1999 Four Winns with a 4.3 Carb that I know will always get me home. I also have a 2011 Cobalt 232 that has a 5.7 GSI 300-C that I take the Rinda and two paddles and wing and prayer just to get back to the dock. Dave-R
 

thumpar

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Carbs are a hundred times simpler than FI and I came from working with engine control modules when I worked as an electrical engineer for GM!

I am guessing you own a Rinda or similar tool when troubleshooting your FI? Same goes for when you troubleshot the FI in your car?
I don't have a Rinda but have eyed them. I do have stuff for cars. There are guys in the Mustang group I am part of taking the FI off their 5.0 engines and switching to carbs. Some of us say they are moving backward and their are others that wouldn't have it any other way.
 

Scott Danforth

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it isnt that fuel injection is faulty. it is the cheap-carp parts its made with that fail.

plastic has no business anywhere near a motor.

i could go on and on about the common failure points of EFI. in a car/truck that gets driven, the car/truck gets replaced/sold/scrapped between the 10-15 year mark when the cheap EFI parts fail because the rest of the car/truck has started to fail.

in a boat with minimal hours per year, the parts will start to fail at the 10 year mark, some making it to 15.

nothing wrong with EFI or a carb. just understand the design life of the components in the system and replace accordingly
 

wengr

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Thanks for all the helpful replies. Interesting stuff. I am really starting to lean towards carb, as the boat I buy will likely be 10+ years old.
 

Lou C

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The other issue is sometimes the marine specific EFI parts sometimes become NLA as the boat gets older, and that can be a real pain. With a carb and mechanical fuel pump, usually you can get them rebuilt and replace the pump without difficulty as they were the same for so many model years. Yes an EFI engine will run better consistently, just like they do in our vehicles, and not need the cleaning carbs seem to need every 5-7 or so seasons.
 

nola mike

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Bigger issue for me with the EFI is that they're a merc-specific black box. If they break, much harder to diagnose. Seems that most car FI issues can be diagnosed/fixed with a $50 OBD-II reader and access to thousands of other people with the same issue. Not so with the mercs. I had some cars with mechanical FI in the 80's...those were pretty sweet I thought. Could diagnose everything with a pressure gauge and multimeter.
 

QBhoy

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Having been victim to a few mpi problems....I still wouldn't change back to a carb. The benefits I have noticed far out weigh getting the mpi niggles dealt with. Once you get a handle on the usual failure points and the cost of the spark plugs (that don't need changed that often), they are night and day in terms of performance, starting and fuel economy.
It's worth mentioning that despite the problems I've had...it has never left me dead in the water.
Have a look at the fuel economy figures (which don't matter to some, but do to me)
My wee boat will cruise at 2200-2300 rpm at about 27mph and only be using 19 litres per hour. Incredible for a V8 engine in any boat. That's a figure that would rival most 4 stroke modern outboards of half or less the horsepower on much lighter boats.
 

QBhoy

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Not to mention the retail value when you decide to sell. The mpi will surely hold its value better as we move into the new age of engines.
 

QBhoy

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Worth noting that I refer to MPI models...not the older EFI. Big difference.
 
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