Thoughts on Mercruiser 4.5 and 6.2

[andrewterri]

Are these engines proven to be reliable? Any experience's? Pro's and Con's? I know they will be more to work on since mercruiser is building everything. Leaning towards 6.2 with 300hp.

 

[achris]

6.2 is still a SBC....

 

[harringtondav]

6.2 is still a SBC....

"SBC"?. Sounds like a TLA. Is this code for still a GM?

 

[harringtondav]

Are these engines proven to be reliable? Any experience's? Pro's and Con's? I know they will be more to work on since mercruiser is building everything. Leaning towards 6.2 with 300hp.

I have the same questions. Unfortunately the jury will be out on the 4.5 for a while. Which is a bummer for me since I expect to be buying a future boat in that displacement and hp. From what I've read on this forum, Merc's success with aluminum block I/O engines is less than stellar.

 

[andrewterri]

harringtonav that is where we are at. We bought a boat last year for an unbelievable price with only 26 hours. it is a little smaller than we wanted and have the boat sold if we are ready to move up. we are looking at a Monterey 238ss with the 6.2. 4.5 is an option but 250hp seems a little light for that size and weight. I am worried about the reliability of the engines. I thought the 6.2 was mercruiser's design like the 4.5. I did not know it was a chevy block. Achris, have you heard if they are going to stop producing that engine like the 4.3?

 

[GA_Boater]

The Small Block Chevy has been around since 1955. Parts won't be drying up any time soon.

Chevy/GMC are still sticking 6.2s in pickups.

 

[aimlow]

Even the 4.5 uses mostly stock Chevy parts. I'll bet Mercruiser got it right this time.

 

[Alumarine]

Even the 4.5 uses mostly stock Chevy parts. I'll bet Mercruiser got it right this time.

Are you thinking 3rd time's the charm?

 

[porscheguy]

harringtonav that is where we are at. We bought a boat last year for an unbelievable price with only 26 hours. it is a little smaller than we wanted and have the boat sold if we are ready to move up. we are looking at a Monterey 238ss with the 6.2. 4.5 is an option but 250hp seems a little light for that size and weight. I am worried about the reliability of the engines. I thought the 6.2 was mercruiser's design like the 4.5. I did not know it was a chevy block. Achris, have you heard if they are going to stop producing that engine like the 4.3?

Don’t even consider a 4.5 for a 23-24’ boat. And don’t fall into the trap of thinking “I don’t need to go that fast.”

The reliability of the 6.2 should be just fine if you take care of it.

 

[Cortes100]

I know nothing about the 6.2 but I do have a 4.5 200hp version. Not what you want in a 23' boat, but here's a few comments on the engine. Mine is in a 18.5' bow rider. Engine itself runs amazing. Super quiet, excellent power, good on fuel. It does pull very good through out the whole rpm range, but the bottom end grunt is awsome. When we were shopping, 18 months ago, the 4.3 was no where to be found except in a few carbed versions.
Working on it was a bit of a challenge, since everything is different than the 4.3. Hah, there is an engine under all those wires and sensors, doesn't look much different than under the hood of your new car.
As for longevity, I cannot comment since we only have about 50 hours on it, but so far so good.
I'm not in the market for a bigger engine / bigger boat, but if I had to buy another one today, and the HP range pointed to the V6, I would not hesitate on the 4.5L

 

[andrewterri]

Thanks for you thoughts everyone and for your review cortes100. I am surprised Monterey has the 250hp 4.5L as the standard engine for a boat that heavy. I am not sure what the difference is between the 300 and 350hp 6.2 but for some reason you can not get the 350hp in that boat even though it is rated for 380hp. I am the same thought as everyone else, go for the larger engine if you have the choice. We have a large family and so I know we would need the higher HP. I really like the 4.3 we have now but at 220hp with the boat (20') fully load it takes some time to get up on plane. that's turning a 14.5x15 4 blade. Best I can do to stay in RPM range. The engine now has about 70 hours but I know that engine is well proven. I am glad to hear the 6.2 is too and sounds like the 4.5 is well on its way.

 

[andrewterri]

Cortes100, It sure would be nice not to hear the whistle and engine noise the 4.3 makes. I have read and heard the 4.5 is really a smooth quite ride

 

[aimlow]

Are you thinking 3rd time's the charm?

Lets see..470, VW diesel, ..isn't there another??

 

[Alumarine]

Lets see..470, VW diesel, ..isn't there another??

Vazer

 

[aimlow]

Vazer

Lost me on that one...

 

[achris]

Guys, the 6.2 (377 cu in) is a 350 stroked. Same block, same bore, same heads.... Different crank. The 350 (5.7L) has a stroke of 3.48" and the 6.2 has a stroke of 3.75"... Everything else is the same. The advantage of the longer stoke is that it makes it closer to a square engine (bore is 4" on both engines), increasing power made at the low-end....

But again, the 'secret' to making engines work nicely, in any size boat is propping. Prop right to the very top of the rev range. If you operate in oceans, or 'big water', like GoM or some of the great lakes, then you're rarely anyway near full throttle for most of the time, you can afford to go a size down on that, and you get a boat that performs brilliantly... I've said it before and I'll say it again... My boat, heavy for it's size, with a 4.3MPI, the 'right' prop is a 19". Takes the revs to exactly 4600 (recommended range is 4400-4800).. With that prop I get to 43knots.

For those of you who don't know what a 'knot' is, yes I'm looking at you jimmbo,

And at 18 knots(whatever that is)

it's the only proper marine term to use when dealing with speed of boats/ships and aircraft.For more details, click here -> https://www.history.com/news/why-is-a-ships-speed-measured-in-knots

But with the 19" prop it doesn't perform 'well' below 2,800rpm. I use a 17" prop, and at WOT I bang on the rev-limiter at 5100, and get just on 40knots. But since the days a year I can run at anything close to full throttle can be counted on one hand, it's moot. The benefit of the 17" prop is that it jumps out of the water on take-off, it isn't affected as much when run up and down the face of swells, and we get some 3 and 4m swells here, I have 'extra' capacity when I have a few more people onboard, or a good day's catch ... For those worried about fuel consumption, I have run fuel tests with both the 17" and the 19" props, and for the same speed through the water, the engine uses the same amount of fuel... Yes the revs are slightly higher, but that's a good thing. The engine's not loaded up as much and will produce less wear and also be easier on the drive....When I bought the boat, with the 165 in it, it had a 17" prop, and it was sluggish and cumbersome (WOT 3900). I dropped it to a 15" and it was a different boat. It felt 'lighter' and was far more responsive... Props can make or break a boat performance wise. When I first changed to the 4.3LX, the dealer, bless him :facepalm:, put a Mirage prop on... TERRIBLE, way too much bow lift, for that hull. I almost sold the boat there and then. But went back to basics and did some proper prop trials. That hull DOES NOT want a prop that produces bow lift. Some hulls do, mine doesn't.... Best props for my hull, In 3 blades, Black Max, Vengence, Laser II.... In 4 blades, Alpha One, Offshore/Vensura. And unless you are DRAMATICALLY under-powered, it's the prop that will make all the difference.

Hit me up with more questions if you need clarification on anything. I've been playing with this boat since 1986, and my parents owner one since I was 10.... I've had a 165, a 4.3LX and the current 4.3MPI in mine, my parents had a 160 in theirs. And when I was a Mariner/Mercruiser dealer I have set up dozens of boats, and advised on many many more.

Chris......

 

[achris]

Vazer

Lost me on that one...

Around 2008... Merc's venture into a 'flat' engine. It was 1.6L 100hp. The engine was inclined at 50 degrees to achieve a low profile so it would fit under a flat floor in things like party boats.... What do you guys call those things? Pontoons?

Anyway, went the way of the Edsel...

Chris........

 

[jimmbo]

For those of you who don't know what a 'knot' is, yes I'm looking at you jimmbo,
it's the only proper marine term to use when dealing with speed of boats/ships and aircraft.For more details, click here ->
Chris......

I've never seen(since 1972) a pressure gauge speedometer that read Knots, only MPH or KM/hr. Maybe the marine industry/society is modernizing as to what 'Proper' is

 

[achris]

I've never seen(since 1972) a pressure gauge speedometer that read Knots, only MPH or KM/hr. Maybe the marine industry/society is modernizing as to what 'Proper' is

You're not looking very hard then....

These are what I found in 10 minutes.... Some pitot, some GPS, but all in knots. And all for sale for purchase now. Most are still in production.

 

[aimlow]

Around 2008... Merc's venture into a 'flat' engine. It was 1.6L 100hp. The engine was inclined at 50 degrees to achieve a low profile so it would fit under a flat floor in things like party boats.... What do you guys call those things? Pontoons?

Anyway, went the way of the Edsel...

Chris........

Possibly Subaru based?? Thanks!