What is the difference in these engines?

[BamaAlum97]

This isn't about an engine problem, so I hope this is in the right forum...

I am considering the purchase of a 2008 Tahoe Q7i. The dry weight of the boat is listed as just a bit over 3000lbs. The standard engine is a MerCruiser 4.3L 190HP V6.

I intend on upping the engine to 220HP. There are two different 220HP engines that are available to me. The first is a MerCruiser 5.0L 220HP V8. The second is a MerCruiser 4.3 MPI 220HP V6.

Please forgive my ignorance about this, but I am a lot of mixed advice on this, even from the dealers. I figure I would put it up here to all you guys with the brains bigger than mine.

So, my question is...What are the main differences in these engines? With my limited knowledge, I believe the V6 would run more efficeintly than the V8 as far as fuel is concerned. Since they are both 220HP, should I expect the performance, speed, etc...to be similar with either? The V6 is actually more expensive, but I know that does not always translate into better fit for my purposes.

The average use for this boat will be for cruising around a lake with a load of 2-4 adults and 1-2 small children and occasionally pulling the previously mentioned children on a tube.

Any info you guys can provide on this is greatly appreciated...

 

[Don S]

Re: What is the difference in these engines?

Please forgive my ignorance about this, but I am a lot of mixed advice on this, even from the dealers. I figure I would put it up here to all you guys with the brains bigger than mine.

So, do you really think asking on a forum is going to get you only one answer???? It won't, it will only confuse you more.

 

[Bondo]

Re: What is the difference in these engines?

Ayuh,......

The V6 is Fuel Injected,+ the 5.0l is a 2bbl. Carb.......

Get the V6,.... By the tone of your post,......
It'll make you Happy........
The Driveability is less finicky..........

 

[Don S]

Re: What is the difference in these engines?

Here is 1 opinion. (EDIT Second opinion, bondo snuck in between posts )
Get a 5.7 MPI, then you will have something.

But with your 2 choices, I would say that both are 220 HP. If you want to do your own maintenance without a lot of special tools, get the 5.0 as it's carbed. If you aren't going to be doing more than basic oil changing and tuneups, then get the MPI.

 

[BamaAlum97]

Re: What is the difference in these engines?

So, do you really think asking on a forum is going to get you only one answer???? It won't, it will only confuse you more.

I fully expect to get a wide varietly of answers. But I figure that on here, I will be spared the dealers spin on the topic since noone on here is trying to sell me a boat. I am only looking for some information about the engines...expected performance...and I know that that info will come with its share of opinions.

 

[Don S]

Re: What is the difference in these engines?

Well hang around ........... there will be more opinions

 

[Bondo]

Re: What is the difference in these engines?

Well hang around ........... there will be more opinions

Ayuh,.........


Just Don't Mention,................ Oil....

 

[Coors]

Re: What is the difference in these engines?

3000 lbs, and 6 adults (kids count as 1/2) , + fuel, and cooler, and assorted carry-ons, and safety equipment= more weight.
Before even dragging someone behind the boat.
You need a V8.
I know, have a 3000 pounder, with a 5.7.
Wish I had a Hemi.

 

[Haut Medoc]

Re: What is the difference in these engines?

Go with the V8.......​

 

[Mkos1980]

Re: What is the difference in these engines?

3000 lbs, and 6 adults (kids count as 1/2) , + fuel, and cooler, and assorted carry-ons, and safety equipment= more weight.
Before even dragging someone behind the boat.
You need a V8.
I know, have a 3000 pounder, with a 5.7.
Wish I had a Hemi.

100% Ditto lol. I'm around 3200lbs and trying to get on plane with 6 people all in the back (NO BR) is not fun lol. Once On plane it'll do 48-50mph but no power to have all the people+ pull something while taking off. My vote is BIGGER! if you can. If not I'd go V8 for more tq.

 

[achris]

Re: What is the difference in these engines?

You will get all the advise you need, and some you don't

I have the V6 MPI in a boat over 4,000lbs. I get 43 knots and at full noise am using 61 litres per hour. At cruise of about 21 knots I use 26 litres an hour. That's one of the most economical boats for it's size.

I sometimes do an overnight run to some islands off the coast about 30 miles. I usually end up doing close to 100 miles on the full trip, carrying all our SCUBA gear (including 8 tanks!), overnight gear and a big 12v fridge. I run a size smaller prop and the boat is just a lively as ever.

I had a carbed V6 previously (in the same boat) and this engine is much nicer in the mid range. I did have an issue with it early on, what appeared to be a lack of mid range power, but it looks like that was just the engine still tight, before fully running in. It's great now.

As for doing your own work... Very little to do on a MPI, just filters, oil and every 10 years change the plugs. The electronics monitors the engine and will alert you and manage the engine if there's a problem. Even if you get a load of rotten fuel the management system will adjust the timing to reduce the likelihood of engine damage. I'm an electronics specialist and I've seen Mercury develop their engine management systems over the last 20 years. They usually wait and see how reliable things are in the automotive world before implementing them in their engines....

Just my experience.

Chris...........

 

[JustJason]

Re: What is the difference in these engines?

I'd say it all depends on your expectations of the boat... and how you plan on using it.
The 5.0 is going to have more torque. And is therefor going to be better at getting the boat out of the hole... but more importantly better at towing.
The boat with the 4.3 should have no problem with tubers, skiers, or boarders... it just may have to be propped according to your expectation of useage.
1 passenger, light load, no towing... the engines should have the same top end within a mile or 2 an hour.
Lots of passengers, medium to heavy load, and towing... the V8 will obviously be faster.... but who tows a skier at 40 with a sterndrive.
If its a family boat... and more importantly if your wife or kids will be driving the boat... get the 4.3 just because its injected... and easier to operate for everyone. It'll be slightly better on fuel costs too.
Now if they had a 5.0 MPI...... that would be a different story...
coz no one ever complains when they have to much power.

Before you settle on a Tahoe... you may want to check out this thread and wait till the outcome of it all before you decide.

http://forums.iboats.com/showthread.php?t=235489

 

[woosterken]

Re: What is the difference in these engines?

I think after reading the topic in boat resteration
about a new tahoe with the stringers pushing through the bottom I would pass on the tahoe.
just my 0.02
woosterken

 

[BamaAlum97]

Re: What is the difference in these engines?

In a perfect world I would get the max horsepower available for this particular boat. However, that is most certainly more power than I need and I am pretty much only choosing between the two options for 220HP.

I think I understand correctly that torque is the key ingredient here. I have had several people mention to me that the V8 will produce more torque than the V6.

That being said, please tell me if my logic is correct here. Torque is measured by the formula: (HP * 5252)/RPM = Torque

The specs for both engines show a max RPM of 4800. If I know RPM and HP, then I can calculate torque. (220HP * 5252)/RPM = 240.7 ft lbs of torque. If I am doing this correctly, then both engines would produce the same torque.

Am I missing something here? Or is it really that simple?

 

[Don S]

Re: What is the difference in these engines?

Cubic inches, and cam profiles also affect torque, Mercruiser does NOT, Never has or ever will publish their torque curves for their engines, and it's not as simple as your equation.

 

[superpop]

Re: What is the difference in these engines?

Get the V8, you can change to a 4V later if you want more oomph. You can do nothing with the v6 if it is not grunty enough with the exception of a different prop. See my sig line below as well.

 

[Maclin]

Re: What is the difference in these engines?

The larger engine will have more torque available lower in the rpm range, thus better acceleration from a deadstop.

If you look at the rpm ranges for those two engines the 5.0 with a 2 bbl carb is not designed to spin as high, so the "low" HP numbers are deceiving. The 4.3 is designed to spin higher and thus "catches up" on the HP but later in the rpm range. If you only look at the HP rating you would think that they run the same in the same boat but the 5.0 boat would run away from the 4.3 from a deadstop.

 

[wca_tim]

Re: What is the difference in these engines?

Both are tried and true set-ups. The 4.3 is a great little engine and would get god fuel economy, etc...
The 5.0 is equally as capable...

fuel economy is probably goign to depend on how you drive it as much as anything else... and is a drop in the bucket relative to the cost of a new boat...

If you're one of those people that might get dissatisfied and want to upgrade, having the v-8 as a statring point makes it a whole lot easier (and cheaper) to move up to a 350 or even a 383 a few years down the road if you want to... The 4.3 doesn't get a whole lot more punch without doing extreme things to it...

I put a new v-6 in last year... and am putting a v-8 in this year. But then again, I don't remember ever owning anything that had "enough" power...

 

[AZSenza]

Re: What is the difference in these engines?

Get the V8. As stated previously, the torque curves are a lot better on the 305. I have the 305 2 barrel carb after having a 350 4 barrel. FIRST THING I'M DOING is adding a 4 Barrel. it even makes better economy with a vaccum secondary and once the back 2 open up the torque should climb quickly along with the HP. the V6 is a good engine but you'll always wish you had more. I wish a 8.1L had been available for my 186! Idda bought it! (NO REPLACEMENT FOR DISPLACEMENT)

 

[JustJason]

Re: What is the difference in these engines?

if your wife is gonna drive it.... get the efi.