Mercruiser 5.0 TKS vs 4.3 MPI

[Scott06]

We sold our 3.0 Mercruiser last year after having owned it for 35 years. About 1250 hours on the clock. Maintenance was by the book and we used E10 for however many years it was available. The carb was adjusted as necessary and I replaced the choke spring once, but the carb was never rebuilt. The motor ran like a top and my annual performance curve was unchanged since 1984.

Was my boat an anomaly, or did the ethanol have something to do with it? I rebuilt the carb in my classic car when it was about 10 years old, but it hasn't been touched either in the last 30 years.

I think you are on the luckier side with both the boat and the car. My 3.0 was in a 1991 I cleaned the carb twice. One of those times It made a big difference in runability/idle/ off idle throttle response, but I rebuilt it due to Black fouled plugs Only to find the choke sticking past rebuild... my family had this boat from when it was 5 years old to 25 years old , like yours still ran great despite really beating the snot out of it skiing and tubing with my kids... 3800-4800 rpm for like an hour straight when we went out. I don’t think the ethanol is a factor one way or another if you use it frequently and burn the fuel.
my 65 gto ive rebuilt the carb3 or 4 times in 39 years but it mostly sits, longest way 8 years.

really for me the mpi vs carb that I can fix the carb model during the summer vs waiting weeks at the mechanic. I know yo can buy the software etc to log on more of a personal choice,each has +/- ... my sea doo Is injected, I spent $450 on software to reset the throttle position sensor zero point. unbelievably able that a 3 % offset in TPS basically makes the thing stall and smoke ,I was changing plugs every two weeks.

 

[Scott06]

Without doubt a 4.3 mpi in the same model of boat as one with a 5.0 carb...will be better on fuel. Let there be no doubt about it.

sure the 4.3 mpi is great , and likely on paper will get better gph... but ok may be 3gph better fuel consumption. Most people’s use you will never see that difference in your wallet. I’m in the NE US so our season is very short 3-4 months. My total fuel bill is like $800 per year.

for me the ability to fix it and not be off the water in such a short season is the key factor In favor of old school Carbs .

 

[Scott06]

Thanks for all the replies. I am leaning toward the 195 with the 5.0 engine. It is also a 2009
Vs the 205 is a 2007. I like the color and interior on the 195 better.

comes Down to how many people you want to take out My 200 sport is comfortable for water sports with 6-8 pp, Ten for a cruise

 

[mr 88]

No I am saying , go with whichever one you think will be a better fit for you. If you are relatively new to boating and end up enjoying it the odd's are in a few years you will be looking for a bigger boat ,consider that . Both boats have decent power plants / Your original post was about a carbed motor vs Injected . The general consensus is ,don't worry about the carbed unit , they are easy to work on ,usually have less issues than a injected and the fuel useage is about the same.Now when Qboy chimes in tell him to go to the Mercruiser forum and compare the post about the 4.3 and in this case the 5.0 .

 

[Bhebert449]

No I am saying , go with whichever one you think will be a better fit for you. If you are relatively new to boating and end up enjoying it the odd's are in a few years you will be looking for a bigger boat ,consider that . Both boats have decent power plants / Your original post was about a carbed motor vs Injected . The general consensus is ,don't worry about the carbed unit , they are easy to work on ,usually have less issues than a injected and the fuel useage is about the same.Now when Qboy chimes in tell him to go to the Mercruiser forum and compare the post about the 4.3 and in this case the 5.0 .

Gotcha. I have another thread about the 195 vs the 205 so I got confused. I am going to look at the 205 this weekend and will be able to compare with the 195. Both are around $15k and have low hours and have been well cared for.

 

[Scott Danforth]

the 5.0 is an SBC. any SBC powered boat that comes with a 2 barrel cast-iron intake such as the 220hp can be upgraded by bolting on a 4-barrel intake in either cast-iron or dual-alloy aluminum. I suggest the edelbrock marine intake and the edelbrock 1409 marine carb. that will take the 220hp (prop) to a minimum of 240hp (prop) and the motor isnt anywhere near the threshold of detonation like the 4.3

here is a link from michigan motors https://www.michiganmotorz.com/rise-aluminum-vortec-intake-manifold-1996-current-p-114.html

here is a link from Jegs https://www.jegs.com/i/Edelbrock/35...eQNimdOXHS4j_ykmQYmOCoE4Pa0l47r4aAsgwEALw_wcB

(its either a barr manifold or a barr manifold with edelbrock cast in it)

then you simply need to buy a 1409 carb and the mercruiser 4-barrel throttle bracket (look at the 5.7)

nothing special about BSFC, it is the law on engine combustion.

EFI in a boat may add drivability, it does not add power or fuel economy. it simply allows the engine to operate just a tad bit closer to the edge of detonation because of the twin knock sensors and the ECM pulling back timing and fueling vs a carb motor.

and most importantly, 20 years from now, you will still be able to repair a carb where most of the EFI parts will be NLA

 

[Scott06]

805359T is the throttle bracket part number. The slave solenoid circuit breaker etc that are on the existing one

 

[QBhoy]

Boy it's not the same hull. It does not have the same torque. It is not worth more. It will wear out quicker. The fuel milage difference isn't even worth discussing. Yes after sitting a week or so the MPI will fire up sooner than the carb. After the 5.0 is started one time it will fire up as quickly as the untill it isnt used for a week or so.. Want a bunch of crap , "really untrue info being thrown about here " . To the OP good luck and buy what you think will make you happier.

The crap I was referring to, was the idea that a 5.0 carb and 4.3 mpi will use the same fuel as each other, like for like. I didn’t say the topic referred to the same hull. Only replied to the idea of if they were the same hull and engines were compared.
so again...I’ll say that the advice given that the 4.3 mpi would not be better on fuel...is utterly poor advice. Fact. Apart from that...why the hell would you want to stay in the Stone Age, if something a little more modern was an option.

 

[QBhoy]

No I am saying , go with whichever one you think will be a better fit for you. If you are relatively new to boating and end up enjoying it the odd's are in a few years you will be looking for a bigger boat ,consider that . Both boats have decent power plants / Your original post was about a carbed motor vs Injected . The general consensus is ,don't worry about the carbed unit , they are easy to work on ,usually have less issues than a injected and the fuel useage is about the same.Now when Qboy chimes in tell him to go to the Mercruiser forum and compare the post about the 4.3 and in this case the 5.0 .

Listen. Honestly. I’m a fan of both. No doubt. Just the 4.3 mpi is hands down the sensible option when both are compared. Jeez...no wonder we are facing a global melt down, if we keep guzzling fuel when we have the option of using a little less for the same result.

 

[QBhoy]

the 5.0 is an SBC. any SBC powered boat that comes with a 2 barrel cast-iron intake such as the 220hp can be upgraded by bolting on a 4-barrel intake in either cast-iron or dual-alloy aluminum. I suggest the edelbrock marine intake and the edelbrock 1409 marine carb. that will take the 220hp (prop) to a minimum of 240hp (prop) and the motor isnt anywhere near the threshold of detonation like the 4.3

here is a link from michigan motors https://www.michiganmotorz.com/rise-aluminum-vortec-intake-manifold-1996-current-p-114.html

here is a link from Jegs https://www.jegs.com/i/Edelbrock/35...eQNimdOXHS4j_ykmQYmOCoE4Pa0l47r4aAsgwEALw_wcB

(its either a barr manifold or a barr manifold with edelbrock cast in it)

then you simply need to buy a 1409 carb and the mercruiser 4-barrel throttle bracket (look at the 5.7)

nothing special about BSFC, it is the law on engine combustion.

EFI in a boat may add drivability, it does not add power or fuel economy. it simply allows the engine to operate just a tad bit closer to the edge of detonation because of the twin knock sensors and the ECM pulling back timing and fueling vs a carb motor.

and most importantly, 20 years from now, you will still be able to repair a carb where most of the EFI parts will be NLA

It defo does add power...the guy is asking about an mpi remember. Mpi give more power than the equivalent era carb. You may be thinking about the efi?

 

[Scott Danforth]

It defo does add power...the guy is asking about an mpi remember. Mpi give more power than the equivalent era carb. You may be thinking about the efi?

No, i have been involved with engines and turning wrenches since I was 3. Definately not thinking MPI. I know the limitations of EFI vs Carb, I know the benefits, limitations and realities.

Prove to me that EFI adds more power.

Having been involved with EFI motors since the 80s, unless you have variable valve timing on a motor with EFI, there is no power benefits or economy benefits over a properly tuned carb.

 

[QBhoy]

No, i have been involved with engines and turning wrenches since I was 3. Definately not thinking MPI. I know the limitations of EFI vs Carb, I know the benefits, limitations and realities.

Prove to me that EFI adds more power.

Having been involved with EFI motors since the 80s, unless you have variable valve timing on a motor with EFI, there is no power benefits or economy benefits over a properly tuned carb.

Hi Scott. Totally realise and aware of your experience. Of which, I’d love to have even half of it some day. No doubt. But in those days..quite simply the mpi always had more power. 4.3 4 barrel, 190,205. Mpi 220. 5.0 carb 220/230...mpi 260. 5.7 carb 250/260...mpi 300. 7.4 carb 310...mpi (although earlier version) 330.
totally agree that if fuelling and settings spot on, carbs do well. But in their factory form same age...always more power in an mpi.

 

[QBhoy]

No, i have been involved with engines and turning wrenches since I was 3. Definately not thinking MPI. I know the limitations of EFI vs Carb, I know the benefits, limitations and realities.

Prove to me that EFI adds more power.

Having been involved with EFI motors since the 80s, unless you have variable valve timing on a motor with EFI, there is no power benefits or economy benefits over a properly tuned carb.

As for the claim that there is no economy benefit. Surely you’ll admit that there is simply no way on earth, that a carb fuelling system with a common shared inlet manifold to all cylinders...can ever be as efficient as a precise and measured atomised dose individually to each cylinder...as with the mpi. It’s just never going to come close Scott. It can’t. Although I’m likely younger than yourself...I’ve been involved and educated professionally (on a larger scale than these type marine engines) with such things for fair number of years previously.

 

[Scott06]

Hi Scott. Totally realise and aware of your experience. Of which, I’d love to have even half of it some day. No doubt. But in those days..quite simply the mpi always had more power. 4.3 4 barrel, 190,205. Mpi 220. 5.0 carb 220/230...mpi 260. 5.7 carb 250/260...mpi 300. 7.4 carb 310...mpi (although earlier version) 330.
totally agree that if fuelling and settings spot on, carbs do well. But in their factory form same age...always more power in an mpi.

I don’t want to add fuel to this cause I’m happy with my carb and your happy with your mpi, but the hp comparisons you give are not apples to apples. These are the 2 bbl engines vs mpi As when merc started offing mpi they dropped the 4 bbl. versions. You have to give some one a reason to buck up $3 k for the higher hp motor. the Michigan Motorz 5.0 carbed partial engine I put in my boat is rated at ... 260 hp, 5.0 mpi.... 260 hp. Only diff between it and the 220 hp TKS version is a chineesium cast iron intake you see all over the web and Edelbrock 1409.

 

[Scott Danforth]

As for the claim that there is no economy benefit. Surely you’ll admit that there is simply no way on earth, that a carb fuelling system with a common shared inlet manifold to all cylinders...can ever be as efficient as a precise and measured atomised dose individually to each cylinder...as with the mpi. It’s just never going to come close Scott. It can’t. Although I’m likely younger than yourself...I’ve been involved and educated professionally (on a larger scale than these type marine engines) with such things for fair number of years previously.

you should do some research. and you should talk to many of the pioneers in the EFI world

a carb will always atomize better than an intake mounted injector nozzle (again, do your own research). not until you get to direct injection with variable valve timing can an EFI motor make more power than a simple carbed motor. however that is because the engine architecture has been modified beyond the capabilities of a simple motor.

a direct cut and paste

Does EFI increase horsepower?
' The answer is: no EFI system is capable of making horsepower, it can only support the power potential of the engine, and the fuel injectors are the limiting factor

Im glad you are happy with your MPI motor. however for a 350, its only making 260hp. at best the 350 mag made 300 hp prop (about 320 crank). the 6.2 MPI makes about 350hp or about 320 at the props. I have built 450hp carbureted 383's for use in a co-workers boat back in the 90's. I had about 330hp at the crank (about 300hp at the props) coming out of my tweeked vortec headded flat tappet small block in the rogue until I decided to go big block.

as a side note, my 3.8 liter 330hp V6 in my college daily driver in the early 90's got 32mpg at 80mph with a big 650CFM double pumper sitting on top of it. when I switched that motor to EFI, I had to change the cam, lost 30hp, and lost 10mpg. shortly went back to the carb

 

[tpenfield]

I am looking at a 2009 Sea Ray 195 sport that has the 5.0 tks engine. This is a carbureted engine, correct? Many of the other used boats in this price range have the 4.3 MPI rated at the same HP.

Any concerns with a carbureted engine on this model? Should I opt for a fuel injected engine?

All too often 'we' see questions like this . . . different sized engine w/ same rated horsepower. . . . and someone wanting to know if they will get the same result in terms of performance.

Keep in mind that "Horse Power" (HP) is merely "Force x Velocity" . . . or in engine speak "Torque X RPM" . . . and the ratings are the maximum that the engine is spec'd to achieve.

So, as an example . . . a small engine capable of half the torque, but twice the RPM as compared to a larger engine would have the same spec'd HP.

In a boating application, the amount of torque and how quickly throughout the RPM range the engine can deliver it is more important than the end-game horse power. That is where the larger displacement engines typically have the advantage over a smaller displacement engine.

It all gets back to the saying that "there is no replacement for displacement"

 

[QBhoy]

you should do some research. and you should talk to many of the pioneers in the EFI world

a carb will always atomize better than an intake mounted injector nozzle (again, do your own research). not until you get to direct injection with variable valve timing can an EFI motor make more power than a simple carbed motor. however that is because the engine architecture has been modified beyond the capabilities of a simple motor.

a direct cut and paste

Does EFI increase horsepower?
' The answer is: no EFI system is capable of making horsepower, it can only support the power potential of the engine, and the fuel injectors are the limiting factor

Im glad you are happy with your MPI motor. however for a 350, its only making 260hp. at best the 350 mag made 300 hp prop (about 320 crank). the 6.2 MPI makes about 350hp or about 320 at the props. I have built 450hp carbureted 383's for use in a co-workers boat back in the 90's. I had about 330hp at the crank (about 300hp at the props) coming out of my tweeked vortec headded flat tappet small block in the rogue until I decided to go big block.

as a side note, my 3.8 liter 330hp V6 in my college daily driver in the early 90's got 32mpg at 80mph with a big 650CFM double pumper sitting on top of it. when I switched that motor to EFI, I had to change the cam, lost 30hp, and lost 10mpg. shortly went back to the carb

Thanks Scott... But it’s MPI, like we discussed earlier. Not efi TBI. Totally different thing. There is no throttle body injected mpi. They have a fuel rail and individual injectors sure. That’s why they are more efficient. Like I said earlier.

 

[QBhoy]

you should do some research. and you should talk to many of the pioneers in the EFI world

a carb will always atomize better than an intake mounted injector nozzle (again, do your own research). not until you get to direct injection with variable valve timing can an EFI motor make more power than a simple carbed motor. however that is because the engine architecture has been modified beyond the capabilities of a simple motor.

a direct cut and paste

Does EFI increase horsepower?
' The answer is: no EFI system is capable of making horsepower, it can only support the power potential of the engine, and the fuel injectors are the limiting factor

Im glad you are happy with your MPI motor. however for a 350, its only making 260hp. at best the 350 mag made 300 hp prop (about 320 crank). the 6.2 MPI makes about 350hp or about 320 at the props. I have built 450hp carbureted 383's for use in a co-workers boat back in the 90's. I had about 330hp at the crank (about 300hp at the props) coming out of my tweeked vortec headded flat tappet small block in the rogue until I decided to go big block.

as a side note, my 3.8 liter 330hp V6 in my college daily driver in the early 90's got 32mpg at 80mph with a big 650CFM double pumper sitting on top of it. when I switched that motor to EFI, I had to change the cam, lost 30hp, and lost 10mpg. shortly went back to the carb

There is no 260hp mpi 5.7. You’re still thinking efi Scott.

 

[QBhoy]

I don’t want to add fuel to this cause I’m happy with my carb and your happy with your mpi, but the hp comparisons you give are not apples to apples. These are the 2 bbl engines vs mpi As when merc started offing mpi they dropped the 4 bbl. versions. You have to give some one a reason to buck up $3 k for the higher hp motor. the Michigan Motorz 5.0 carbed partial engine I put in my boat is rated at ... 260 hp, 5.0 mpi.... 260 hp. Only diff between it and the 220 hp TKS version is a chineesium cast iron intake you see all over the web and Edelbrock 1409.

Hi
A 4 barrel 4.3 in those days was about 190-210 Hp at best. The mpi 220. The 5.0 4 barrel was from memory about 230/240 (I think)...5.0 mpi is 260hp. The 5.7 4 barrel is 260hp. 300hp from the mpi. No 4 barrel of those days was ever as powerful as the mpi slightly later version. Apples for apples.

 

[Scott Danforth]

Thanks Scott... But it’s MPI, like we discussed earlier. Not efi TBI. Totally different thing. There is no throttle body injected mpi. They have a fuel rail and individual injectors sure. That’s why they are more efficient. Like I said earlier.

you obviously think I dont know that. however Im glad you like your MPI engine.... you still cant make more power with EFI than you can a carb. the combusion mix of the engine (dynamic CR, cam profile, rocker geometry, combustion chamber and of course bore and stroke) is what determines an engines power.