Merc. I/O Improvements & older 4.3L vs. newer 3.0L

Rookster

Petty Officer 1st Class
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Mar 12, 2017
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226
The lowest rated 4.3 can be easily modified to more power for very little money. Vortec heads and a 4 barrel intake and carb can be obtained easily, slapped on in a weekend and that 155hp rated motor is pushing closer to 190-195

And if I lack the skills, tools and ability to avoid blowing up my motor due to human error, what might it cost in parts and labour to do that modification...and could/would most average mechanics or marinas do it?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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47,310
if you understand righty-tighty, you can do it. simply unbolting parts, cleaning, bolting other parts back on, stabbing the dizzy and adjusting a carb.

most places will gladly take your money to work on things. however if your paying someone to turn wrenches, then make sure you have deep pocket books for this already expensive hobby.

you could swap heads and intake yourself, find the parts, order gaskets on-line, etc and have the job done for under $500 if you shop around (reconditioned heads, used intake, reconditioned carb), or about $1200 for new parts (new heads, new intake and new carb)

paying a marina to do it means you pay list price plus their book labor. that $480 set of new cylinder heads ordered on-line and delivered to your house lists $1530 each at a dealer - that is 3060 for the pair. and 4 hours to install each that $230 new intake from Chevrolet or Summit lists about $530 at a dealer and 3 hours to install that $15 set of valve cover gaskets list $30 each at a dealer..... you get the idea. paying a dealer to update a 4.3 to vortec heads with a 4-barrel will cost you a ton of money

at that point if you lack the skills, buy a boat with the 4.3 4-barrel or 4.3 MPI to begin with.
 

Rookster

Petty Officer 1st Class
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Mar 12, 2017
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226
Thanks, Scott - that just about puts it all into perspective! Honestly though, my bigger concern above skills and money is...TIME!
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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To swap heads and intake on a 4.3 is a 4 hour job, 6 hours if you never did it before

You have spent more time perseverating over the motor and trying to convince yourself the 3.0 is more than a turd in the past few weeks
 

Rookster

Petty Officer 1st Class
Joined
Mar 12, 2017
Messages
226
To swap heads and intake on a 4.3 is a 4 hour job, 6 hours if you never did it before

You have spent more time perseverating over the motor and trying to convince yourself the 3.0 is more than a turd in the past few weeks

Now now...fair enough, but I don't intend to keep this up forever. That said, stay tuned...there's more to come!
 

thumpar

Admiral
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Jun 21, 2007
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6,138
The one thing you can be sure of is that with either one you will soon want a bigger one. I went from a 2.5l to a 5.7l EFI and now want the 383.
 

DCMacGuy

Seaman Apprentice
Joined
Sep 5, 2013
Messages
36
The 2.5 liter was rated in the 110 / 115 / 120hp range
The 3.0 was rated in the 130 / 135 / 140 range and 160hp with fuel injection.

Was the EFI Volvo 3.0 the 160HP one?

I've never seen a Mercruiser 3.0 rated higher than 140 - my 3.0mpi is 135.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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The one thing you can be sure of is that with either one you will soon want a bigger one. I went from a 2.5l to a 5.7l EFI and now want the 383.

and after the 383 your will be building a 468....then a 496...then a 540....

I have been eyeing an all aluminum 613 cubic inch Art Morrison block.....however the Admiral says no.
 

Rookster

Petty Officer 1st Class
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Mar 12, 2017
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226
Right now I'm bound by my 3500lb tow capacity - more power means more weight, so one step at a time...issue is that for what I'm willing to spend on a boat, I'd have to buy something either older than I want to or in poor condition, to get a 4.3L, but we'll see...
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Right now I'm bound by my 3500lb tow capacity - more power means more weight, so one step at a time...issue is that for what I'm willing to spend on a boat, I'd have to buy something either older than I want to or in poor condition, to get a 4.3L, but we'll see...

3500#....minus the #1000 trailer.....minus the 600# gear and fuel.....minus the 400# of stuff in the tow vehicle leaves you with a 1500# boat (an 18' tinny outboard or a 15' fiberglass 3.0 I/O)

given your limitations of tow vehicle, I would be looking for a starcraft with a 135hp merc
 

Rookster

Petty Officer 1st Class
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Mar 12, 2017
Messages
226
3500#....minus the #1000 trailer.....minus the 600# gear and fuel.....minus the 400# of stuff in the tow vehicle leaves you with a 1500# boat (an 18' tinny outboard or a 15' fiberglass 3.0 I/O) given your limitations of tow vehicle, I would be looking for a starcraft with a 135hp merc

Your estimates are pretty close for sure - I do have a bit more wiggle room and can (inconveniently) go up to just over a 2,000# boat if it's on a light weight trailer. Just means less luggage and no gear - which is doable. I'd rent a truck to get boat to the park, then it would sit there permanently. Tow vehicle would only be used to launch/retrieve boat to/from lake, and pre-season/post-season service or repairs that I can't do myself. No long haul trips between home and lake.

That said, I was also considering a 2004 Doral 170 OB with a 2004 direct injection Ficht 2-stroke 115hp OB. The 17ft Doral is only 1650lbs, so a 115hp OB motor should give it about the same performance as a 3.0 I/O motor in a 2100lb boat. Sound about right? And thoughts on a 115 OB 2-stroke compared to the 3.0? I hear the direct injection models like Ficht were really good after 2002 (almost as good as ETEC)?
 

Rookster

Petty Officer 1st Class
Joined
Mar 12, 2017
Messages
226
No Title

Having a blast with my Merc. 3.0! 2000 Crownline 180BR - great hull design...moves awesome, lots of speed and power - more than enough for a new boater with small family. Doesn't take much to feel fast on the water. Guess it's all perspective - to a fighter pilot, a 500mph commercial airbus is slow. The 3.0 jumped out of the hole quickly, was powerful enough to push my 18ft 2200lb Bowrider into a virtual upright wheelie with four people aboard...after I forgot to trim down before accelerating out of the hole (crazy rookie mistake) lol.
 

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DCMacGuy

Seaman Apprentice
Joined
Sep 5, 2013
Messages
36
Glad to hear you are enjoying it! The 3.0 really is a great little performer...
 
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