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

[Bondo]

What engineering improvements were made on the Merc. 3.0L I/O between 1990 and 2000? Similarly, what about the Merc. 4.0L I/O in that same decade?

Ayuh,... Not exactly what yer askin' 'bout, But,...

The Alpha, Gen.II came out in '91, so anything newer is a current production drive,.....

 

[Rookster]

Thanks Bondo - Scott actually gave an excellent response yesterday, at 12:27pm in post # 2 of this thread.

 

[Rookster]

While we're on the discussion of 3.0 vs. 4.3, and I4 vs. V6, any thoughts on these two power plants:

Yamaha 4.3L V6 I/O (early 90s)
Mercury Sport Jet M2 EFI V6 (early 2000's 2-stroke jet drive)

Thoughts on quality, affordability, efficiency, parts availability, reliability, longevity - and all that usual stuff?

 

[bruceb58]

You don't want the Yamaha drives. Parts are scarce and people able to work on them are even more scarce. They were forced to stop selling them in the US due to patent issues.

 

[Rookster]

Thanks for confirming - I also heard they are less efficient and less reliable.

If we don't have any Jet gurus here, I may have to post on the Jet forum...just wondering is the Merc. M2 Sport Jet V6 EFI 2-strike is any good - I hear it's basically a Merc. Outdrive with lower section modified from Prop to Jet?

 

[Bondo]

If we don't have any Jet gurus here, I may have to post on the Jet forum...just wondering is the Merc. M2 Sport Jet V6 EFI 2-strike is any good - I hear it's basically a Merc. Outdrive with lower section modified from Prop to Jet?

Nope,.... It's a jet-ski driveline,... a lain over outboard hooked to a jet-pump,....

Not an I/O at all,...

 

[bruceb58]

Thanks for confirming - I also heard they are less efficient and less reliable.

What are you referring to?

 

[jkust]

Out of your suggested engines (mercruisr 3.0, mercruiser 4.3, 2 stroke jet), in the years you are suggesting, I would select anything with a 4.3. They are cheap, plentiful and massively more powerful than a 3.0. The sound is also much more pleasing than the high pitched drone of the 3.0 liter or a 2 stroke jet for that matter. The jet boats of that 90's era are mere toys compared to the jet powered boats of today. I would only select a 1996 or newer 4.3 because of the improvements that were made that year to the heads and intake that increased the HP and TQ an appreciable amount.

 

[bruceb58]

I would only select a 1996 or newer 4.3 because of the improvements that were made that year to the heads and intake that increased the HP and TQ an appreciable amount.

Many 96's didn't have the Vortec heads yet. GM came out with the Vortec heads in autos/trucks in 96 but marine didn't get them right away.

 

[Rookster]

What are you referring to?

Referring to your statement about Yamaha I/Os

 

[Rookster]

Yup, think I missed out on a 2001 Ebtide 4.3 going for same price as the 2000 Crownline 3.0 I'm set on. Difference being Crown comes fully serviced and dealer guaranteed in great mechanical and structural condition with only minor cosmetic issues that I can correct in my driveway, while the Ebtide was a private sale from someone who purchased a cottage that came with the boat, and buyer of the cottage/seller of the boat didn't want the boat. So who knows what it went through or what I'd have had to spend on any maintenance issues...that's the typical situation I'm in with what appear to be good private deals - but what lurks beneath is unknown.

 

[jkust]

Many 96's didn't have the Vortec heads yet. GM came out with the Vortec heads in autos/trucks in 96 but marine didn't get them right away.

Well true....they had to use up their current stock of 95's. Gotta make sure you know what you are looking at because the boat can be a 96 but the engine can be a 95 pre vortec head model.

 

[bruceb58]

Referring to your statement about Yamaha I/Os

I kinda find that hard to believe since the Yamaha 4.3L is the same GM engine that everyone else uses.

 

[Scott Danforth]

what appear to be good private deals - but what lurks beneath is unknown.

I have been burned by dealer purchases more often than private sales.

 

[bruceb58]

I have been burned by dealer purchases more often than private sales.

Likewise...fortunately for me, the problem that the dealer didn't tell me about was covered under warranty.

 

[H20Rat]

While we're on the discussion of 3.0 vs. 4.3, and I4 vs. V6, any thoughts on these two power plants:

Yamaha 4.3L V6 I/O (early 90s)
Mercury Sport Jet M2 EFI V6 (early 2000's 2-stroke jet drive)

Thoughts on quality, affordability, efficiency, parts availability, reliability, longevity - and all that usual stuff?

Ironically I kind of own both... (well, sort of...) I've got a '95 mercruiser 4.3, and a 2001 Sportjet V6.

The sportjet is a perfect river shallow water boat, and it will yank the arms off a skier. Drawback is that it is a thirsty beast! It is a v6 2 stroke after all... It also doesn't like going slow, it is fairly inefficient at less than cruising speed. Once you are up to cruising, mileage isn't that much different. The other huge drawback is that it is $$$$ to repower. Whereas the 4.3 is dirt cheap.

 

[Scott Danforth]

However the yamaha drive parts and support are nearly non existent

 

[Rookster]

Thanks guys - Yamaha and Seadoo...off the list! Always were but thought I'd put them out there to get your thoughts for confirmation.

 

[Rookster]

as far as a merc 3.0, the 1990 and older motors are all 2-piece rear main seals and come with a smaller flywheel the 1991 and newer 3.0 have a 1-piece rear main seal and come with a larger flywheel. other than the short lived EFI 3.0, there have been a few changes in the ignition system, however the base motor is the same for 1990 and older and 1991 and newer

On this note, I understand that the minor changes that the 3.0 went through from 1990 to about 2005, include horsepower upgrades ranging from 115hp all the way to 140hp. Apparently some of that had to do with the way the HP was measured (at the crank vs. the prop) and use of bigger carburetor head? They also named them differently throughout the 90s between the 3.0L and the 3.0LX? The LX meant bigger carb head for higher power rating and/or meant it had power steering? Not sure - info found during research was very confusing. Furthermore, after 2000, Mercruiser made the 3.0 MPI and the 3.0 TKS???

Then I read where the best way to simplify it all is to look at ROM ranges at WOT. If it reads 4200-4600, you have something closer to the 115HP. If it reads 4400-4800, then you have something closer to the 135HP.

In the case of the one I'm close to getting, it is a year 2000, which reads only Mercruiser 3.0 Liter. But according to the dealer, it does have power steering. The label on the carb also reads 4400 to 4800 RPM at WOT, indicating that it's 135HP. Is that a correct assumption?

Can anyone experienced with the Mercruiser 3.0 comment, conform or shed some light on this confusion?

 

[bruceb58]

Bottom line...at the RPM that you cruise at, which will likely be between 3000 RPM and 4000RPM, they will all have the same HP in that range.

There is a guy on here that hasn't responded on this thread yet. He is very proud of the fact that he has a 140HP 3.0. Problem is, he has one of the last ones that was measured at the crank instead of the prop! LOL