Is it worth swaping a 4.3 MPI for a 5L ?

ric · **Posted:** Tue Feb 17, 2015 7:32 pm

The only reason EFI engines make more power than carb is because that's how they market them.

There's nothing about a 5.7GXi 320hp Volvo motor that makes it do some magic sauce over the 5.7GL that makes 260hp. The horsepower difference is because Volvo detuned the GL motor to make 260hp. They can't sell a carbed and fuel injected motor both making 320hp, everyone would by the carb'd motor cause it would be cheaper to buy and cheaper to maintain for the same power level.

The 5.0 merc in my boat making 220hp is only making 220hp cause of the intake manifold and tiny carb. I could easily throw on a normal carb and take off the tiny mercarb and make the same 260 hp as the Mercruiser 5.0 MPI. What would be the point of selling the 5.0 MPI then? Or I could even install the same camshaft as the 5.7 300hp MPI and make 300hp.

It's all marketing and sales. That's why I bought my 215 ssi with the base 5.0 220hp engine. Way pay thousands more for crappy EFI that breaks when I can just order a new carb/intake/cam for $1000 and make the same hp?

TX H210SS · **Joined:** Thu May 27, 2010 9:10 am **Posts:** 1488

I ran a Carb 2bbl on my 5.7 in a bayliner 2050SS for 10 years with no reliability probs. That boat was way lighter and would get it. I wouldn't be afraid of the Carb one bit. A properly tuned Carb is golden. In 10 years I had ZERO fuel issues and never touched the Carb and that boat spent countless hours towing skis, tubes and boards. Never failed to fire right up....that reliability argument is total BS.

I personally would buy a 5.0 Carb over a six banger efi every time. Same goes for a 5.7 Carb over a 5.0 efi. I'm sorry to say it, but she lied....size matters.

LouC · **Posted:** Wed Feb 18, 2015 8:29 am

I do agree with the comments about EFI vs Carb and here is why:
the main advantage of EFI is better cold starts and smoother running when cold. They can make more power but its not a huge difference. They are good for people who do not understand chokes and carbed engines. If you run lawn equipment such as mowers, blowers and weed wackers or even snow blowers in winter, then you understand carbs n chokes. I grew up with them so no worries there.
The draw back of EFI vs carb is this: Cost and eventual parts availability. If you have to do certain repairs it costs more. If you keep your boat a long time or buy older boats and restore them as some do, the manufacturers do not keep making these parts forever. You can be SOL because you can't get an ECM for a 10-12 year old boat. Fuel pumps cost a fortune. With a carb engine you can go out and get a new carb for at most 350 or so. Set it up and away you go.
305 EFI vs carb, no big deal, carb, but make it a 4bbl. Same with the little 4.3. Works great with a Q-Jet.
Carbs are better for hobbyists on hot rods or boats. EFI is great don't get me wrong, but on an older boat or hot rod I prefer carbs 100%.

Jsyphil · **Posted:** Thu Feb 19, 2015 5:41 am

LouC wrote:

I do agree with the comments about EFI vs Carb and here is why:
the main advantage of EFI is better cold starts and smoother running when cold. They can make more power but its not a huge difference. They are good for people who do not understand chokes and carbed engines. If you run lawn equipment such as mowers, blowers and weed wackers or even snow blowers in winter, then you understand carbs n chokes. I grew up with them so no worries there.
The draw back of EFI vs carb is this: Cost and eventual parts availability. If you have to do certain repairs it costs more. If you keep your boat a long time or buy older boats and restore them as some do, the manufacturers do not keep making these parts forever. You can be SOL because you can't get an ECM for a 10-12 year old boat. Fuel pumps cost a fortune. With a carb engine you can go out and get a new carb for at most 350 or so. Set it up and away you go.
305 EFI vs carb, no big deal, carb, but make it a 4bbl. Same with the little 4.3. Works great with a Q-Jet.
Carbs are better for hobbyists on hot rods or boats. EFI is great don't get me wrong, but on an older boat or hot rod I prefer carbs 100%.

Amen to that. Agree 100%.

ric · **Posted:** Thu Feb 19, 2015 7:44 am

I can replace my whole engine with a complete running rebuilt one cheaper than replacing the fuel pump and ECU on a FI engine.

What's the advantage again? Runs better cold? Last I checked my boat cruises and idles at 160 degrees.

Jdpber · **Posted:** Thu Feb 19, 2015 9:00 am

my 5.0 is EFI and if anything major in the refi department goes i will slap a new highflown intake and carb on in a heart beat.

Boats need to be simple and simply put carbs are simple. i can explain to a woman how a carb works and she actually grasp 25% of the concept 10x faster than i can explain to the same woman how EFI works and she may grasp 1% of EFi.

LouC · **Posted:** Thu Feb 19, 2015 10:44 am

Actually if you look at a throttle body EFI and look at those components and then take apart a Rochester Quadrajet, you might think the EFI is simpler. And I have to say I have had far less trouble with my vehicles that came with EFI than the ones I had with carbs. Yes younguns, some of us bought new cars that had ONLY carbs. And drove them in Northeast winters. Here's the ones I've had and how they did:
1965 VW Beetle, same engine was shared with my FiberFab Dune Buggy: 1200 cc, 40 hp, 1bbl Solex. As long as the choke was set right it would start.
1972 Chevrolet Impala 350/2bbl: the years of cheap emissions control and idle limiter caps on the mixture screws. It never ran well cold until the damn caps were pried off and the mixture was set right.
1970 Ford Torino 302/2bbl: it would start fine but the choke never opened! Took it all apart and found an air leak in the vaccum system that sucked hot air off the exhaust manifold to warm the choke spring
1975 Olds Delta 88 350/Q-Jet 4bbl cat converter. Due to the addtion of the cats in the mid 70s the engines could be tuned to run a bit richer and ran much better than the '72 Chevy at least till we tuned the Chev the way we wanted not the way the EPA wanted lol.
1980 Honda Civic 1300 cc 3bbl Keihin carb. This was one of Honda's CVCC engines and it just never ran right. Stalling stumbling, surging etc.
1982 Mazda 626 2000 cc 2bbl carb. This one with cat converter ran fine for a carb engine.
1988 Mazda 323 1600 cc EFI. Big difference, started easily no roaring fast cold idle.
After that they were all EFI. Only repairs to the EFIs have been a fuel pump on our '88 Toyota at 11 years 115,000 miles.
Current: '98 Jeep Chrysler EFI no repairs to the fuel system but the ECM had to be replaced at 12 years old. '98 Subaru, had a few sensors go (speed sensor 2x, knock sensor 1x) but that's it.
07 Jeep Grand, no repairs so far.

In a cold climate if you had a work boat you had to use in 30* weather like many do here you'd want EFI I think. But for repairability and ease of getting a new carb, for old boats used only in warm weather as I said carbs are fine. But driving the first EFI cars we had, after years of chokes, high idle speeds and stalling in winter, well it was a revelation let me tell you that.

TX H210SS · **Joined:** Thu May 27, 2010 9:10 am **Posts:** 1488

I have had carbs on two boats, three cj jeeps, two trucks, one bronco and two Chevy cars and will say you had to know how to hold your mouth just right for cold starts on every one of them. On the last boat I would give it one pump on the throttle and then give it slight throttle for immediate cold start..but if there was a problem it took minutes to pull the carb off and take to my brother for rebuild. The mechanical fuel pump ssn was simple and cheap. The fuel cell on this boat was crazy expensive and rivaled the swap cost on the diesel 1 ton.

deafwish · **Posted:** Sun Mar 01, 2015 12:55 am

Any developments on this, Mark?

meinmelb · **Posted:** Mon Mar 02, 2015 1:40 am

Insurance has paid me out so I have cash burning a hole in my pocket.......

I am in no real hurry as the motor is running fine at the moment and with winter approaching our boating activity's will slow and give the mechanic more time to work on the boat. I am also searching for a good second hand 5.7L V8 if one comes up but they are as rare as rocking horse sh1t.

I have also spoken to the Mercruiser engineer who has basically said that for the effort required is really is not worth it to swap the 4.3MPI for the 5L carbie. Had it been the 5.7(carbie or MPI) then the added power would be worth it. Also because it is a stern drive the weight is at the back of the boat so any increase in weight will need to be substantively offset by increased power and torque. Also the design of the Four Winns hull means that what little increase there may be, will just not be felt in increased acceleration. The only really noticeable difference will be fuel consumption.. upwards!

Now if I could find a nice used 5.7 MPI complete mercruiser motor to drop in that is a whole different story.

PS one of the guys we ski with has access to bits to make motors go faster, so over a beer or 12 we discussed a 50HP nitrous kit or a supercharger... :mrgreen:

mmm sounded good at the time, not so sure now.

ric · **Posted:** Mon Mar 02, 2015 9:42 am

yeah you need to find a new engineer. You will see a substantial increase in power by going from a 4.3 to a 5.0 even if they are "rated" the same.

meinmelb · **Posted:** Tue Mar 03, 2015 2:27 am

ric wrote:

yeah you need to find a new engineer. You will see a substantial increase in power by going from a 4.3 to a 5.0 even if they are "rated" the same.

Thanks Ric. One of the privileges of an online internet forum is the many different view points that people have. As you can imagine everyone has and I believe is entitled to their opinion, and if course that is exactly what was asked for in this thread. Many have stated their opinions and I have used this as education to state my claim for the swap. This forum as you would expect was not my only on-line reference and I spent many hours researching the options (too much time actually) and found may opinions with very little substance based on fact.

To suggest that a Mechanical Engineer with intimate knowledge of the power and torque figures of both motors, employed by Mercruiser as an advisor to the boat building industry to specify power packs to them, and who has no vested interest in the swap, that he is some how misguided in his recommendation, is perhaps stretching the "entitlement of opinion" and suggests you are better qualified. If you do however have the power and torque curves for both motors on paper I would love to see them and compare to what I was told. If you are also able to quantify the delivery of any power increase into acceleration based on the weight, dimensions, and hull geometry of the H190 I would happily pay you for this calculation and again compare to what I was shown.

The engineer and my marine mechanic (who will gain similar money either way) both feel the swap will provide "some" power and torque increase but not sufficient to feel any difference in the "seat-o-the-pants meter". I think everyone agrees there is no replacement for displacement, so I am looking for the 5.7 instead. :mrgreen:

ric · **Posted:** Tue Mar 03, 2015 7:18 am

Yes he's wrong. 100%. I'm not even going to explain why there's 40+ years of literature based on Chevy performance and why the V8 is better than a V6.

Hint: Torque.

www.iFourWinns.com

Is it worth swaping a 4.3 MPI for a 5L ?

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