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

Rookster

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

Here's a document I found online pertaining to a 1999 Four Winns 170 3.0, with 135HP rating at the prop:
 

Attachments

  • photo260832.jpg
    photo260832.jpg
    50.7 KB · Views: 0

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
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.

The 3.0 longblock is all the same parts (block, head, crank, pistons, cam), the change was the induction (carb or efi) and SAE rating method.

The induction was added by mercruiser or volvo or OMC.
 

Rookster

Petty Officer 1st Class
Joined
Mar 12, 2017
Messages
226
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.

The 3.0 longblock is all the same parts (block, head, crank, pistons, cam), the change was the induction (carb or efi) and SAE rating method.

The induction was added by mercruiser or volvo or OMC.

Curious - is it at all simple/affordable to add fuel injection or EFI to a 3.0?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296

Rookster

Petty Officer 1st Class
Joined
Mar 12, 2017
Messages
226
In this market, the 3.0 is actually the most common marine engine - most boats for sale have the 3.0 motor.
 

Rookster

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

Check out this engine photo - see the shiny brass coloured section...doesn't that look like a newly replaced part? Is it part of the carburetor (showing my ignorance of engines)?

Also, notice how far back it sits in an enclosed area - wouldn't it be less accessible than an I/O that's under a large sunpad and behind a bench seat, which would be more accessible from the sides than this (seemingly less accessible) jump seat configuration?
 

Attachments

  • photo260907.jpg
    photo260907.jpg
    185.3 KB · Views: 0

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
That is a holley 2300 series 2-barrel. The zinc dichromate dip is bronzish in color. However most original marine carbs are painted, so it was replaced

However from the bowl on it, it is most likely not a marine carb.

The remainder of the seats, etc come off/out for serious service
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
Regarding the fuel bowl on the Holley. It might be factory config, as there is a steel fuel line hooking up to it. On swaps, you usually see a hose. This is a Merc, but Volvo almost always used the Holley 2300, and the Volvo service manual(Volvo not aftermarket) shows a that type of bowl on their 3 liter engine

Access to the engine looks pretty good compared to a V6 or V8

As for a 3 liter in an 18 ft boat, unless you never or rarely run outside of no-wake zones, you will tire of it very soon and will wish you had at least a 4.3. I have an 18.5 with a 5.7 and have never said "I wished I had gotten a 3 liter, a 4.3, or even a 5 liter."
 
Last edited:

Rookster

Petty Officer 1st Class
Joined
Mar 12, 2017
Messages
226
Yup - it's a Volvo 3.0. Regarding the wake zones, you're saying that wakes slow down 3.0 liter boats?
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
I said "unless you never or rarely run outside of no-wake zones, you will tire of it very soon and will wish you had at least a 4.3."

If you were regularly wanting to run at higher speeds, the 3 liter will leave you wanting more. If you were only to boat where it was no-wake zones, then a 3 liter is more than enough
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
I said "unless you never or rarely run outside of no-wake zones, you will tire of it very soon and will wish you had at least a 4.3."

If you were regularly wanting to run at higher speeds, the 3 liter will leave you wanting more. If you were only to boat where it was no-wake zones, then a 3 liter is more than enough
Or in other words...if you like going slow, the 3.0 is fine! :)

If you are going to boat at higher altitudes or with many people in the boat, you will want something bigger than a 3.0.
 

Rookster

Petty Officer 1st Class
Joined
Mar 12, 2017
Messages
226
I said "unless you never or rarely run outside of no-wake zones, you will tire of it very soon and will wish you had at least a 4.3."

If you were regularly wanting to run at higher speeds, the 3 liter will leave you wanting more. If you were only to boat where it was no-wake zones, then a 3 liter is more than enough

Ah, ok - Gotchya.
 

Rookster

Petty Officer 1st Class
Joined
Mar 12, 2017
Messages
226
Brief history of 4.3 (going from memory so I may be off on one or two of the changes) Introduced in 1985 model year as flat tappet, 2-piece rear main seal replacement to 229 (3.8)
1986 - received 2-piece rear main seal
1987 - received center bolt valve covers and roller cams
1992 - received balance shaft (and different harmonic damper)
1996 - received vortec heads
1999 - crank pilot changed
2000 - non-adjustable rockers, plastic timing cover

Back on the topic of the 4.3 being more capable than the 3.0, I was looking at a 1992 Larson Lazer 180BR 4.3XLT, and when I did a bit of research I found that the power rating for that Merc. V6 ranged from 155hp to 185hp! That reminded me of your post regarding the changes...and I realized that not every 4.3 is created equal - and some are not much better than the 3.0, especially considering the extra weight of a V6 with only a 20hp gain in the worst of cases (155hp over 135hp). Realizing that's not the norm, it is something to watch out for and be certain as to which V6 version a boat has...correct?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
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

The 3.0 is the 3.0. Not much can be done with it.

Yes, you can get a variety of different pistons for the 3.0 (taken from the sbc), however there is only one head design, and short of a custom grind, there is only one cam.
 

H20Rat

Vice Admiral
Joined
Mar 8, 2009
Messages
5,199
Back on the topic of the 4.3 being more capable than the 3.0, I was looking at a 1992 Larson Lazer 180BR 4.3XLT, and when I did a bit of research I found that the power rating for that Merc. V6 ranged from 155hp to 185hp! That reminded me of your post regarding the changes...and I realized that not every 4.3 is created equal - and some are not much better than the 3.0, especially considering the extra weight of a V6 with only a 20hp gain in the worst of cases (155hp over 135hp). Realizing that's not the norm, it is something to watch out for and be certain as to which V6 version a boat has...correct?


That part you are leaving out is torque, very important for a marine environment! The lowest merc that you mentioned, the 155hp, also has 230 ft/lb of torque. (highest rated 4.3's are around 280 ft/lb of torque) The highest rated 3.0l gets you around the 170 ft/lb area. Pretty big difference! If you track down a dyno graph, the v6 will also hit that peak torque earlier.

If the 3.0l can't get the boat out of the hole to actually get the RPM's to use it, it makes for one very underpowered boat even if the top end HP is somewhat similar. (which is the typical 3.0l experience. A dog out of the hole but if you can get on plane it is ok.)


Same thing happens when you compare the top end v6's to the low end v8's (5.0l) Both are rated for 220hp, but the v8 gains an additional 50 or so ft/lbs of torque.
 
Last edited:
Top