Merc 4.3 or 4.5 power

Cortes100

Petty Officer 2nd Class
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Apr 30, 2006
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175
I have done a lot of surfing and can't find too much info on actual performance tests on these new 4.5L 200hp versions.
I am looking at NEW boats and have a decision to make. Yes this does come down to personal usage but what would be the best logical choice to make??
Both boats are the same 18' brand/model.. Pricing is close, the 2015 a couple bucks cheaper. New on the lot.

2015 factory tower and swim platform. 4.3 TKS 190hp
2016 NO tower or platform but the new 4.5L MPI-200 hp

Either engine should have no problems moving a 18ft, 2400# boat. I've always owned a carbed unit and never had any issues.
So does a guy pick the added options, tower/platform, or go with the newer tech engine setup??
 

Alumarine

Captain
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Feb 22, 2005
Messages
3,684
Are you talking about Merc I/O's?
If so, then the 4.5 is Merc's newer design I believe.
Personally I'd stick with the 4.3 just for parts and service availability.

Just my 2cents.
 

Willyclay

Captain
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Sep 8, 2006
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3,239
I think the 4.3 is a great engine and know nothing about the 4.5. MPI would be great but my experience with carbed motors is the same as you. Our son has a 1995 model 4.3LX (4-barrel carb) in his 19ft-2in. bowrider that will still tickle 50MPH on the speedo with four adults. Do you need an 18 footer to do more than that? Good luck!
 

jkust

Rear Admiral
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Aug 2, 2008
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Wow...was thinking it was a 4.3 MPI not carb. My vote is the three generations newer 4.5 vs a carbed 4.3. A 2400lb 18 footer is on the light side and I'm betting it doesn't have a huge gas tank either. A 4.3 carb will push is just fine but there is more to ownership than fine. My last boat, newer than my current, was a 3100lb dry weight 18 footer and the 4.3 carb did 'fine'. 51.3mph on gps but grew to dislike carbs for all of their shortcomings compared to MPI much less the more modern 4.5 design. Best side by side comparison I've seen compared two identical Sea Rays one with the 5.7 MPI 300hp and the other with the new design 6.2liter MPI 300hp and the new 6.2 walloped it on hole shot then the 5.7 beat it on top end. The new design 4.3 et al, should have more lower and midrange as I understand.
 

lineman09

Petty Officer 2nd Class
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Jun 10, 2011
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126
I had a carbureted 4.3 L MerCruiser in a 2002 bayliner 185 and it pushed it well but I have a new 200 hp Volvo Penta in a 19ft .. The top end is similar but the difference in Low end and power coming out of the hole is substantial ,I believe the new MerCruiser's are direct injected also ... after have owned both now I believe I would probably go with the 4.5 L MerCruiser !!
 

R055

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Jul 13, 2015
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I think it comes down to if you like/need the tower/swim platform on the 2015.
 

briangcc

Commander
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Jul 10, 2012
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2,089
Test drive them both and see which one works for you. And show up unannounced so the marina doesn't have time to warm up the engines prior to your arrival - being warm already would make the start easier on the carb'd model.
 

R055

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Jul 13, 2015
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579
Test drive them both and see which one works for you. And show up unannounced so the marina doesn't have time to warm up the engines prior to your arrival - being warm already would make the start easier on the carb'd model.

A properly adjusted tks carb will cold start pretty easy.
 

roffey

Commander
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Nov 22, 2012
Messages
2,184
I have a newer 4.3 TKS motor. I can tell you from experience the motor starts effortlessly every time, other than breaking out of winter hibernation. if I had the option of 4.3 TKS or the 4.3 MPI I would go with the MPI.
 

fishin98

Chief Petty Officer
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Nov 28, 2009
Messages
521
Go over to the Baylinerownersclub (BOC) site look at threads from people who own boats with the 4.5L motor. I would not be surprised that a V8 is in the works from Mercruiser. I read a article posted there on why Brunswick decided to develop their own motor...Basically came down to GM saying that they will no longer be producing the basic engine components for marine engines in the near future.
 

jkust

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4,942
Go over to the Baylinerownersclub (BOC) site look at threads from people who own boats with the 4.5L motor. I would not be surprised that a V8 is in the works from Mercruiser. I read a article posted there on why Brunswick decided to develop their own motor...Basically came down to GM saying that they will no longer be producing the basic engine components for marine engines in the near future.
They already developed them (the new tech v8's) and have been in boats for a couple years.
As mentioned above, better low end torque for the design reasons they detail. To me it is whether you go with a previous gen MPI or a new Gen. Every technology has its up side and down sides and this far along, the upsides of carbs are eclipsed by a country mile with MPI. Sure you can easily clean or even replace a carb if you had to and would be cheaper once the subject carbed engine was out of warranty but it's turn of the previous century technology that was limped along way too long.
 

H20Rat

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Mar 8, 2009
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5,199
I believe the new MerCruiser's are direct injected also ... after have owned both now I believe I would probably go with the 4.5 L MerCruiser !!

Although I love the concept of direction injection, very few manufacturers are doing it correctly and sticking a single injector in the intake.. (so the disclaimer, I don't know what Mercruiser is doing...) Pure DFI engines will carbon up the intake valves, it isn't a matter of 'if', but 'when' will you be pulling the intake manifold and doing a full walnut valve cleaning.
 

lineman09

Petty Officer 2nd Class
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Jun 10, 2011
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126
Although I love the concept of direction injection, very few manufacturers are doing it correctly and sticking a single injector in the intake.. (so the disclaimer, I don't know what Mercruiser is doing...) Pure DFI engines will carbon up the intake valves, it isn't a matter of 'if', but 'when' will you be pulling the intake manifold and doing a full walnut valve cleaning.
After further research..the new mercruisers are MPI. I run a 4.3L DI volvo penta so far so good ., I guess time will tell!!
 
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