2.0 150HP vs. 2.5 150HP

[4Speed]

Any idea what the speed difference would be between a 2.0L 150 HP & a 2.5L 150 HP on the same boat. I assume more cc's, more torque, bigger pitch prop at same RPMs = more speed. Any idea what to expcet on the speed end? Boat is a 18'6'' Baja that has a hull alone weight if 1,400 lbs...Gear & Driver est 1,800 lbs. Both weights are w/o motor.

[LPB]

Don't waste you time with the 2.0 no balls,I've got a SST-120 motor which is a race verion of the 2.0 with 26cc heads,a stock XR6-150 2.5 liter on the same boat will pull me 4 boat lenths to 60 mph,and the sst 120 is 180 hp,the sst will out run the xr6 on the top side but its 180 hp John LIGHTNING POWER BOATS

[Scream And Fly]

I believe Viper Ronnie started out with a 2.5 150 and with a little (okay, a lot) of grinding and porting, etc, it made a lot of power. A lot.

Greg:)

[Reese]

you and the Baja will be much better off with the 2.5.

To answer your question, technically there should be no real speed difference between two motors with the same HP...150 hp is a 150 hp regardless how you slice it. If you prop to peak HP, both motors might use a different props but the end result would be the same speed.

One thing that would be different is how quickly each motor hit it's top speed...the 2.5 would get there a lot sooner.

[stray cat]

Are we saying that boats are the same as street cars,there is no substatute for cubic inches?

[1BadAction]

Originally posted by Reese
you and the Baja will be much better off with the 2.5.

To answer your question, technically there should be no real speed difference between two motors with the same HP...150 hp is a 150 hp regardless how you slice it. If you prop to peak HP, both motors might use a different props but the end result would be the same speed.

One thing that would be different is how quickly each motor hit it's top speed...the 2.5 would get there a lot sooner.

nope, the 2.5 has more torque than a 2.0. so, if they both turned 6000 rpm, and the 2.0 could only turn a 25p prop, but the 2.5 could turn a 28, the 2.5 is faster.

[Reese]

Are we saying that boats are the same as street cars,there is no substatute for cubic inches?
Yes, Cu.In. are always better just as long as we don't pay too big a price in added weight.

1BadStream:
Peak HP...not peak torque is what determines top speed...if both engine produce the same HP (150) they will produce similar top end numbers regardless of its size.

Torque is a good indication of how quickly top speed will be reached and no one props a boat to peak torque.

A 150 hp 2.0, 2.4, 2.5 and 3.0 litre engine (assuming equal weight) will all produce equal top end numbers.

[1BadAction]

Peak HP...not peak torque is what determines top speed...if both engine produce the same HP (150) they will produce similar top end numbers regardless of its size.

NO, even 500 HP is nothing unless you have enough torque to do the job. it takes HP AND torque to make a boat go, and since the engines both have 150hp and the 2.5 has more balls, it will be faster. yeah 10,000 rpm looks good on a dyno but if it only turns a 10 pitch prop its not worth ****. since we are concerned with real boats and not dyno queens, the 2.5 is faster. torque lets you turn a bigger prop at the same r's. therefore more speed. if you dont believe me get a vector with a stock xr2 2.0, and i will run my vector with the 2.5 xri. whatever prop you want to run, whatever prop i want to run, and I WILL beat you everytime- and thats with the best 2.0 150 merc ever made. i just got done testing the xr2 that we just got redone, and the 2.5 was 5 mph faster. the 2.5 that i have actually has 5 lbs LESS compression too give of take a few on all cylinders.

[Reese]

What do you think weighs more 150 lbs. of feathers or 150 lbs. of bricks?

If you said they both weigh the same then we're getting somewhere...;)

Two engines producing the same HP will mathematically and by the laws of physics produce equal top end numbers...regardless of what kind of torque they produce.

Obviously a motor with more torque will get the job done faster...but both motors will end up giving you the same top end numbers...there is nothing else to argue about.

Your 2.5 litre engine was faster than the 2.0 because it produced more HP...and I don't even have to put it on a dyno to prove that point.

I don't want to confuse 4speed...let at least agree that a 2.5 is a better all around engine for his Baja...;)

[Glowone]

okay...if I may comment. The 2.5 is better and a 3.0 is even better. It really depends on your budget. The question really is how much do you want to spend?

A 150hp 2.0 XR2 in nice condition will run about $2000.00 and in my opinion is the best "bang for the buck" . The XR2 uses alot of the 200hp parts and is a more robust engine than a rugular 150hp. (XR2 is important!)

If you get to a 2.5 litre your going to be twice that.

I am interested in who is right...Reese or 1badstream. I see both points. I know in race cars, torque is key to winning races but it is not because of a top end differences but because you can accelerate out of the corners better.

I dont know enough to comment about the torque v. pitch question.

[rev.ronnie]

So I have found.

[GP-1]

Well.... Actually you'd have to lay the torque curves next to each other. Most likely the 2.5 is gonna make more torque, but if they make the same horsepower (do they?) they would have an equal top speed if they could both be propped appropriately....I have no idea where the power peak is for either engine, but since HP=Torque @ 5250 rpm, and these fishing motors probably make peak horsepower before 6000 rpm, they're probably close in peak torque too... Yea, the 2.5 probably has more at lower RPM -- hence the edge in accelleration -- but with the correct prop, they should be awful close in top end..

[transomstand]

The issue is, two different engines with a 150 Hp "rating". The manufacturers are allowed a substantial variance in true HP while still maintaining the HP rating. I have to think that on the dyno, the 2.5 makes more real horsepower.

[Reese]

did the manufacturers use a pretty wide variance, they also had years where the HP figures were Crankshaft vs. Prop Shaft.

Regardless of the HP rating there is no doubt that the 2.5 had much better torque as well. In either case the 2.5 is a substantially better engine for this application compared to the 2.0.

BTW...a used 2.5 is pretty damn cheap.

[msm]

you have the patients of a saint.

[Glowone]

Not as cheap as a 2.0 :)

If you really want a bulletproof motor with lotsa torque you should get a Yamaha 2.6 Litre Excel. The Mercs will blow up alot sooner.

You can pick em up really cheap (if you can find em) because everyone is a "Merc Head"....still not sure why...hmmmm

Kinda off the subject a bit.

Sorry if I offended anyone :)

[1BadAction]

Originally posted by msm
you have the patients of a saint.

oh yeah, and why is that? :rolleyes:

[msm]

Because he knows what he's talking about and takes the time to explain it in multiple attempts and more and more detail without becoming frustrated.....a very rare quality.

[Reese]

I ain't no saint...but I been around long enough to see very harmless topics turn into outright wars.

Something as simple as "what is the best mota oil" can quickly turn into a name calling, credential questioning, ball busting free for all.

When you look back, those fights were over some pretty insignificant issues...I just don't think it's worth getting too emotional about it.

[1BadAction]

Originally posted by msm
Because he knows what he's talking about and takes the time to explain it in multiple attempts and more and more detail without becoming frustrated.....a very rare quality.

i guess i dont have a clue then,- having built 3 different turbo rotary rx7s and then ending up converting them over to mild lt1 v8s that ran mid 10's on street tires, all on me and my freinds pockets with no help from our parents when i was 16-19 years old. drawing f'ing civil **** in autocad at home untill 3am on the weekdays to finance my projects - then taking a boat that NOBODY ON THIS WHOLE BOARD could stop bouncing and fixing it in 3 months. then with that boat, testing it with both a 2.0 and a 2.5 (didnt have a 2.4 or i would have tried that to, although i suspect that to be closer in performance to the 2.0) running 25 gallons of fuel through the efi 2.5 and 35 gallons through the carbed 2.0 (even tho they were ran the same hours) - just to find the right prop. after that, on the same day so i had the same conditions, i tested the 2.0 then in a 30 minute window i had the 2.5 on the boat and running 5.5 mph faster. it does help the shop i work at is only 5 blocks away from the lake, with a chain hoist and the 2.5 hanging there waiting.

only getting 77.5mph from the 2.0 150hp and then 83mph from the 2.5 150hp on a hydrostream vector hull with 15 gallons of gas, rear seat, full safety gear and an anchor, i guess i dont know anything about what these motors will do. actually, i am thankful that my grandfather loaned me his xr2 to test, i thought i may be able to get a little more out of the boat with a 35 lb lighter motor on the back. that wasnt the case.

[175checkmate]

1badstream, You got the monster to stop bouncing out of the water. What was the problem and how did you fix it?

[Hunter]

The only time engines of different displacement but of equal horsepower can be considered equally effective would be when they are both at peak horsepower.

In practical application, this would only be possible in vehicles with gearboxes that keep the engines in their most effective RPM range. If that's what you'd prop to, fine but be ready to wait.

The reason that a 2.5 will smack down a 2.0 is that outboards have only one gear and the 2.0 comes up short on torque at all other RPMs (and vastly so at holeshot) where most of us spend most of our time anyway.

[1BadAction]

Originally posted by 175checkmate
1badstream, You got the monster to stop bouncing out of the water. What was the problem and how did you fix it?

the details will become declassified early next year. before i run my mouth too much i want this hull to be perfect at all speeds. i am still looking for more speed, and to get a 55-60 bobble out of it. i have single handedly kept the bondo industry in the clewiston area in bussiness for the past 2 months trying different designs.

i will probably end up having my own mold splashed from this hull, because it is ALOT different from what hydrostream originally designed. I want a new vector just like this, but i cant get it unless i have it made.

[espen]

I think to talk torque are BS big time.... its very frustrating and should only be used for a engine developer to look if its any easy posible gain to be made . engines shoud be compared with horse power at different rpm or maybe a using range hp figure..maybe from 2500 to 5500??? Or dyno runs !!

[Reese]

why do you think torque is BS???

A 300 hp 2.0 would be a very different animal compared to a 300 hp 3.0. Both these engines would have exactly the same HP and vastly different and torque curves.

[Glowone]

I think that both sides of this discussion are correct.

Pitch determines top-end and acceleration depending on the pitch being higher or lower.

I think that all parties agree that the 2.5 has more torque than the 2.0 and should accelerate faster.

Given the same pitch prop the boats would go the same top speed.

It makes sense to say the the 2.5 could accelerate the same as a 2.0 with a higher pitch prop due to the fact that the more torque would make it accelerate faster. The higher pitch prop would conceivably have a higher top end.

The 2.5 turnung a higher pitch prop has nothing to do with its torque. Both engines could, in theory, turn the same pitch prop.

There is more to selecting an engine than top speed. Top speed is great on the river but I have out accelerated faster boats and let them cavitate in my wake for awhile. :)

Hey, I have a 2.0 XR2 and it is a great engine. It runs very strong and is almost bullet proof. I run the thing full throttle all the time and never had a single problem.

If I ever get a 20' boat I would opt for the 3.0 liter anyway. In five more years we will be atalking about how great the new "3.4 Liter" is and how the 2.5 lacks power.

I also must say I agree with Reese, lets not get too "mad" about these topics. The fact that we are all reading this website kinda puts us in a "brotherhood". Most of my friends dont know what the heck Im talking about half the time :)

My two cents.

[1BadAction]

3.4 L ha ha. they already did that remember LoL. if they make another it might be good if it revs a little and is sized and weighs less than a refridgerator. :D


why do you think torque is BS???

A 300 hp 2.0 would be a very different animal compared to a 300 hp 3.0. Both these engines would have exactly the same HP and vastly different and torque curves.

no kidding, a 300 2.0 would be retired to the dyno shop, because it wouldnt have the ballz to get a boat on plane. 13,000 rpm maybe? even 120 motors that are on ultra lite race boats are only 180 hp.

i am not going to comment on torque is bs, but i would find it funny when somebody tries to mod that little honduh he so loves to make car power numbers, id pay to see the look on the guys face when the boat wouldnt get on plane. try to tell an inboard boater how good a HOT car camshaft works on a boat, you'll get laughed off the lake. do you ever wonder why even ultra fast blown inboard boats hardly have any cam lope? :)

[Rickracer]

" then taking a boat that NOBODY ON THIS WHOLE BOARD could stop bouncing and fixing it in 3 months "

Several of us said right from day one what the problem was, but nobody would/could fix it on the trailer at the lake. :rolleyes:

[Laker]

An SST120 or XR2 motor at 165-180hp is SO Much different than a 2.0l champ motor at 300hp.. The ultimate of 2.0l racing mercs. Peak hp of the 2.0l champ motors were around 9700rpms..
Torque band of a 2.5 150 is FAT and Wide, about 35% Stronger at most rpms including peak depending on whos data you believe. Compaired to the XR2 or a SST120 it peaks lower but hp is still close... Torque is measured... hp is mathmatics.

[Superdave]

another pissing contest. Man it gets old.
Dave

[espen]

Sorry it seems like I did not manage to get it clear what my wiew was.
If we could compare hp for hp at different rpms it would much easier to compare engines. All outboards are just max hp rated ,same on cars. If you look at a turbo diesel car and a gasoline engine of the same max output its easy to get fooled ...
The turbo diesel version have maybe twice the hp or more
at the rpms you need it most and the hp on demand at a usual driving situation is like a twice big gasoline engine.
I think the talk of torque are a term from the inigeers that confuses a lot of people . I dont say that torque does not matter ...of course it does ! High torgue means more hp and thats what we want ! As much as possible all across the rpm band of the engine and with the speed range of the fast boats the engines have to rev also to widen the envelope witch the engine has to operate.

The xr2 adjusted under the offshore rules of UIM gives about 220hp.
The 2,5l block is lighter than the 2l xr2, there has been problems with the pistons in the xr2 with the new art pistons the life span is longer ,the skirts cracked. The 2,5l has more ports and a big potensial for tuning . The xr2 has nothing in its design that spells high performance its just a fish engine used for lower cost racing.

Ok I understand that the word BS is a powerfull thing to mention

:D

[Reese]

I'm not up on what engines produced what hp or torque for each model year.

I can tell you this, peak hp and nothing else determines top speed...regardless of engine size (liters) or rpm.

Let's add a little fun to this thread...I'll donate $25.00 to S&F (which I should anyway) if I'm wrong. I say that two engines (equal weight) producing equal hp (crank or prop) will produce the same top speed.

Torque or engine size (liters) has zero to do with it. I'll even through this in...each engine can produce that peak hp at very different rpm's (5,500 vs. 6,500) and will still produce the same top speed.

Torque is obviously important since we don't measure HP on a dyno, but we don't prop to peak torque either.

So if anyone want to play (this is supposed to be lighthearted guys, no flaming) I'll donate the $25 if I'm wrong, if you are...you donate $25...so, who's in...:)

[David]

In a well ordered world the outboard companies would publish torque curves (or HP curves, I can do the math).

Maybe Bass and Walleye boats can go back to doing comparison tests. They have tested different manufacturers 200's on the same boat. Once they compared the pro max and civilian versions of the Merc engines on the same boats.

Of course HP or torque is not the whole story. There is gearcase drag, propellers, set up, etc. But a torque curve would be good information.

Its too much to expect Hot Boat or Powerboat to do comparison tests.

sorry, that shot belongs in another tread:)

[Jerry Ridenour]

wouldnt it be safe to say that on this type of boat(as heavy as it is)both motors,being correctly propped.the 2.5 would have to be faster,if for no other reason-we all know that 2 liter needs a smaller prop to get up and going.therefore giving the cubic inches of the 2.5 the advantage because it can accelerate just as fast with a larger prop.come on guys,we all know cubic inches has an advantage.and lets be realistic.whichever motor he uses,he will want it propped best for all around use.but i also agree with reese.150 hp is 150 hp.but sometimes you cant use it the same way...

[Glowone]

I wont bet with Reese because I agree. A boat with a 2.0 would not be set up the same as a boat with a 2.5. One of the boats would have to have a less than optimal setup.

Torque does not equal horsepower. An engine can have alot of Torque and lower horsepower and vice versa. When most new motors come to market both Torque and HP are usually increased.

Ofcourse the 2.5L is better it is the next generation. I would rather have a 2.0XR2 than any I6. I have to defend my XR2 a bit...she treats me well.

I got my new Hot Boat issue and I had to hunt to find the outboards. When I did they were all 3.0L. If you aheva a heavy boat you will need the extra torque to get it moving.

[1BadAction]

Originally posted by Glowone
I have to defend my XR2 a bit...she treats me well.


hell yeah, the xr2 on the old mans bass boat has never had a bolt loosened in the powerhead since it was new in nov. 1984 and there is times we have ran 40 miles to get somewhere on the lake fishing. point it @ 290* on the compass put your foot to the floor and not let off for 35 minutes. np oil injection, original everything except impeller, lu seals, plugs, coils, and wires- and it still has 125 +/- 2lbs on all cylinders. nothing but merc premium plus oil and 93 octane. :cool:

[espen]

T.rex has showed us what is possible with a 2l !
Our discusion has shown what big acomplishment that realy is to
outrun 2.5l s !
The problem with torque numbers is that they are rated at max torque and that is different from engine to engine.
Maybe boats should be rated for planing speed trust power or amount of hp needed to get the boat planing...
Espen

[Rickracer]

...that even if a motor is rated at a given horsepower, that doesn't necessarily mean that that's what it makes. There is that 10% rule, which makes for a possible total of 20% (or more) difference if one motor is over and the other under. And we know sometimes rules are bent. :D Also, there are dog motors, and there are motors that run exceptionally well, right off the same assembly line. If you actually had both on the dyno, and they were equal in power, at whatever rpm range it happened to be, then top speed should be equal as well, provided they are both propped to operate at their max power. My guess is that doesn't happen very often. :cool:

[espen]

thats truth Rickracer...
and maybe the 2l and the 2,5 150 has different output from factory. A 2l are maybe using less fuel ?
Espen

[Mercman80]

Is the 2.5 150hp heavier than the 2.0???

[Muskoka2]

Is the 2.5 150hp heavier than the 2.0???
I believe my Daughter's '02 150 XR6 weighs 406!