Will swapping 3.0 heads gain me a few HP?

[Mile-High Mariner]

Re: Will swapping 3.0 heads gain me a few HP?

Okay, boys, the Union Jack flies on both your flags, so put the gloves away.<br /><br />Here's my opinion, in a nutshell: Mercruiser's use of the various bits and pieces coincides with GM's manufacturing schedules and practices. The 2.5 litre 4-cylinder was discontinued by GM, but Mercruiser still had a stockpile of the 2.5 heads sitting 'round gathering dust, so they used them up and fudged the numbers for the 3.0L. In essence, it IS a derated 3.0LX, producing less power than the LX, but probably not 20hp less. Finally running out of 2.5 heads in 1993, Merc "consolidated" the production of the little 4-cylinder Mercruiser into just the 135hp 3.0L. Now, new for 2006, they're giving up a little bit more horsepower with the fuel-injected 3.0 MPI (too long delayed, in my opinion), rated at 145hp.

 

[bandit86]

Re: Will swapping 3.0 heads gain me a few HP?

when I was looking for a more powerful engine for my chev tracker to turn the monster truck tires, I was looking at the chev iron duke engines, which is the 2.5. There are boards and write up on getting this motor to 300 hp naturally aspirated. There are all sorts of cams and parts available, and most parts should be interchangeable. Unfortunately I dont have the link any more. <br /><br />One thing to keep in mind, horsepower sells engines, Torque wins races. A 3.0 is probably a stroked 2.5. Stroker engines are known for putting out better torque curves, then engines that rev high. Horsepowere is determined as (torque X Rpm) /5252. For example, 100ft/lbs@5000rpm will be the same horsepower as 200ft/lbs @2500rpm. Exact same amount of work, just at lower rpm, easier on the bearings and drivetrain. Dependig on the application, you may want to have lower rpms but more pulling torque. <br />My 2.5L BMW puts out 189hp, not much torque, doesnt move well till its reved above 4000rpm, wouldnt go well in a heavy boat , but would make a nice motor for a lightweight boat

 

[craze1cars]

Re: Will swapping 3.0 heads gain me a few HP?

Originally posted by Mile High Mariner:<br /> Now, new for 2006, they're giving up a little bit more horsepower with the fuel-injected 3.0 MPI (too long delayed, in my opinion), rated at 145hp.

Well this is interesting and I agree long overdue. I hadn't heard they were finally coming out with a 3.0 MPI. I did a quick Google search and could find nothing....even Mercruiser's website doesn't mention this at all. Are you sure?

 

[tommays]

Re: Will swapping 3.0 heads gain me a few HP?

i believe its a throttle body MPI is to much money for a base motor<br /><br /> http://www.marinepowerusa.com/ <br /><br /> http://www.marinepowerusa.com/eng specs/181.htm <br /><br />marine power USA has been selling a 3.0 for a while now<br /><br />tommays

 

[craze1cars]

Re: Will swapping 3.0 heads gain me a few HP?

Thanks, Tommays...I never even heard of them. I guess they're a smaller competitor to Mercruiser and Volvo? <br /><br />But High Mile Mariner specifically said 2006 3.0 MPI....HMM, was this a typo? If not, where did you find info about this production motor? Even if it actually is TBI and not MPI, I still haven't heard about it. Would like to know more.

 

[tommays]

Re: Will swapping 3.0 heads gain me a few HP?

its kind of strange because theres a marine power europe that is part of merc<br /><br /> http://www.marinepower.com/;jsessionid=1iuedzwshqutl <br /><br /><br />tommays

 

[newport dave]

Re: Will swapping 3.0 heads gain me a few HP?

I'm having a hard time believeing that there will be any new engines or engine systems that will be released in 2006 by any of the OEM's.<br /><br />The reason is that they will need to redesign/reengineer every engine in their 2007 line up (under 500HP). So why change an engine for 2006 only to have to change it again for 2007?<br /><br />Why will they need to redesign their product lines for 2007? There will be BIG changes in store for '07 model year marine engines due to the catalyst based emission standards becoming law in California. Not too sure about other states at this point, but they won't be far behind. <br /><br />That means NO more carbureted engines (ding dong the carb is dead) and maybe a 3.0MPI. It also means catalytic converters. I don't know why nobody is talking about this right now, but it's coming.<br /><br />Dave

 

[Cptkid570]

Re: Will swapping 3.0 heads gain me a few HP?

In simplifying this entire discussion -- if you turn a 2.5 liter motor into a 3.0, how much difference would the extra horsepower really really make? Would the performance difference really be worth the time, effort, and money? Going from a 120hp 2.5 to a 140hp 3.0 isn't like you are dropping a 4.3 or a 5.0 liter motor into your engine.<br /><br />How much difference are you needing or expecting? And, you have to ask yourself if you really need the extra hp. I could take out my 3.0 motor and put in a V10, but my wife will still scream at me when I go over 25mph.

 

[tommays]

Re: Will swapping 3.0 heads gain me a few HP?

well my 19 ft boat came with a 3.0 LX there were 2 upgrades a 4.3 and a 5.0 which were big dollars in a low cost boat<br /><br />it does 41 with the 3.0 the factory claimed about 45 with the 4.3 and 50 with the 5.0<br /><br />the big advantage was getting up on plane quicker as its to rough here about 90% of the time to run fast anyway<br /><br />tommays

 

[craze1cars]

Re: Will swapping 3.0 heads gain me a few HP?

Originally posted by cptkid570:<br /> Would the performance difference really be worth the time, effort, and money? Going from a 120hp 2.5 to a 140hp 3.0 isn't like you are dropping a 4.3 or a 5.0 liter motor into your engine.<br /><br />

I'm not proposing changing a 120 2.5 to a 140 3.0. I was proposing changing a 115 3.0 to a 135 or 140 3.0 with a head swap. But that's just nit-picking...I understand the spirit of your question. So here's the answer(s):<br /><br />YES, if it is as cheap and easy as doing a simple used head-swap from a different generation of 3.0 as I initailly proposed in my first few posts. In my mind, a 17% or more HP boost for under $500 in parts and a winter weekend spent tinkering would be time and money well spent in my mind. That's a cheap investment for better accelleration for pulling watersports (more important) and maybe a slightly higher top speed (less important to me.) That's a heckuva lot cheaper than a replacement boat or powering up to a bigger motor.<br /><br />NO, if its more expensive and difficult than that, or if it would need a lot more changes than just the heads. Or if it simply won't work.<br /><br />This quandry is exactly why I started the topic, to help me decide whether or not the change would be feasible, and if it would get the results I'm hoping for.<br /><br />The other aspect to this is extra cylinders create more dead weight. The old power-to-weight ratio thing is worth considering IMO. So jumping from 115 to maybe 140 with the same 4 cylinder motor and no corresponding increase in weight might theoretically make the boat perform ALMOST like it would with the much heavier 190 HP 4.3 liter V6 installed, and dragging down harder on the stern of the boat. Not saying that's fact, but it's just another thought...

 

[craze1cars]

Re: Will swapping 3.0 heads gain me a few HP?

Originally posted by cptkid570:<br /> And, you have to ask yourself if you really need the extra hp...my wife will still scream at me when I go over 25mph.

I missed this when I read it the first time. Do I really NEED the extra HP? <br /><br />Do I really need a boat?<br /><br />This is all about my wants. <br /><br />And my wife screams at me when I run over 25 as well....must be contagious! Then again she screams at me when I rip the tires loose in the hot rod once in a while. That's just background noise and has no place in this discussion.

 

[Cptkid570]

Re: Will swapping 3.0 heads gain me a few HP?

I recently bought another boat.. a 1985 searay 26'. It doesn't run right now and I bought it as a fixer upper. I joke with my wife and tell her that I'm going to put my 3.0 liter motor in it because all she likes to do is go idle speed anyway.

 

[trog100]

Re: Will swapping 3.0 heads gain me a few HP?

craze1cars.. the idea of getting that 20% power boost just by swopping heads is a bloody good one and would have been well worth doing.. it went thru my mind prety much as it went thru yours..<br /><br />with my digging into the situation it turned out that my particular none LX 3.0 wasnt one of the 89 to 94 hybrid ones anyway so it all became academic..<br /><br />however i did dig up enough info on the situation to convince myself %100 that the new low power 3.0 engine was a nonsense and more about keeping the market range just as it was before discontinuing the 2.5..<br /><br />a plus and minus to this one.. the plus ..your engine is pretty much as powerfull as the LX and u have no worries.. the minus of course being a future project that would have given u pleasure to do is now lost.. he he..<br /><br />i know i love fiddling.. i assume u do.. <br /><br />trog<br /><br />ps.. and just for a laff.. what is the actual difference tween the 3.0 and the 3.0LX (the simple answer that one puts out 115hp and one puts out 135hp not counting as an answer of course) was the very very first question i ask on this forum.. he he..<br /><br />needless to say i didnt get much of an answer.. at least u have..<br /><br />basically i got insulted and accused of having too much time on my hands by wanting to know such a thing by a certain well known and much loved forum guru..<br /><br />either way i now consider myself the self acknowledged expert on that particular question.. he he he..<br /><br />a belated happy new year to all.. trog

 

[paulie0735]

Re: Will swapping 3.0 heads gain me a few HP?

32 posts and nobody seems any the wiser, lots of theory’s and bruised ego’s but still nobody wants to commit on the first posted question. Actually more confused now than ever might be putting it mildly. If what’s being suggested is correct than;<br /><br />a) You have 135hp engine but it has the old 2.5lt head on it. If this is true than simply doing the swap will achieve your aim!!! <br />b) Your engine is a 135 with 115 stickers on it. If this is true than swapping the heads will achieve nothing!! <br />c) You have a 'designed for the market' engine and there’s more to the hp difference than just the head!<br /><br />I sure hope somebody knows somebody who actually knows the answer and can put us all out of our misery.

 

[craze1cars]

Re: Will swapping 3.0 heads gain me a few HP?

Originally posted by paulie0735:<br /> 32 posts and nobody seems any the wiser, lots of theory’s and bruised ego’s but still nobody wants to commit on the first posted question. Actually more confused now than ever might be putting it mildly. If what’s being suggested is correct than;<br /><br />a) You have 135hp engine but it has the old 2.5lt head on it. If this is true than simply doing the swap will achieve your aim!!! <br />b) Your engine is a 135 with 115 stickers on it. If this is true than swapping the heads will achieve nothing!! <br />c) You have a 'designed for the market' engine and there’s more to the hp difference than just the head!<br /><br />I sure hope somebody knows somebody who actually knows the answer and can put us all out of our misery.

OK, one more essay from me and I'll probably let this die.<br /><br />That's a very accurate summary, Paulie, though I don't know that many egos were harmed in the making of this thread. And I'm certainly not feeling any misery. Theories are about 5% what I was seeking, and 95% of what I got...BUT...it is always fun to chat, so I'm honestly not complaining. Every theory (or restatement of the SAME theory AGAIN) bumps the post to the top, so maybe someone in the know will stumble across it and try to weed through all the mumbo-jumbo that ended up in this thread and clogged up the works (much of it from me!)<br /><br />In a perfect world, I was seeking info from someone (experienced Merc mechanics, especially) who has attempted and failed, or attempted and succeeded. Or someone who has seen dyno #'s or head flow data from Mercruiser or any other source on these various combos. Haven't found that person yet. Maybe one will pop up. Or maybe it'll motivate someone with too much time on their hands to actually TEST the theories. In the meantime, we're still stuck with a few similar theories that have been repeated over & over again in different words.<br /><br />In my mind, a theory becomes fact only after it's been tested and proven. This can't be done on paper or with thorough research. A theory has not been DIS-proven does not make it a fact. As for Trog's (and a few others) theory, I'm not yet sold, and unfortunately his method of delivery has upset some people at times, but I for one genuinely respect his thoughts and research and I fully acknowledge he just MIGHT be right. It's certainly proven in his mind as he's made very clear. But without a field test with stats, I can't accept it as fact.<br /><br />I just fear that because of Trog's strong involvement on this post, a few other very knowlegeable people on this site who may have had some knowledge to add, chose not to participate at all out of dislike for him. So the rest of us lose. This is regretable, but the nature of the beast. Trog, I do not say this to be mean....you know as well as I do that you've been in a battle with more than one person on this site and I'm just pointing that out to others who may not have witnessed them in the past. Besides, this is just a theory of mine...and I acknowledge that it hasn't been proven as fact yet. And I also acknowledge that maybe some maybe didn't participate out of a dislike of ME. Anything is quite possible...<br /><br />It's still fun, though.... I enjoyed EVERYONE'S input and hopefully others who may have been watching this thing develop (likely in disgust) may just chime in yet. Not to disrespect anyone, but only to offer some fresh insight or facts. If you don't like what Trog says, just don't read his posts! Skip them and say your own thing. It really is that simple...

 

[Mile-High Mariner]

Re: Will swapping 3.0 heads gain me a few HP?

Craze - sorry for the delay. I have been in communication with Mercruiser customer support over issues pertaining to my stern drive system, and got the skinny from them. A Dogpile search will get you hints like what I've attached, below, but Mercruiser itself is playing it close to the vest on this one.<br /><br />MerCruiser - Mercury Marine<br />... Mercury Product Family Details. 3.0 MPI - 145 HP ... Mercury 225 EFI Saltwater FourStroke. Bravo Three Drive Features. Mercury Inflatables. Trash >> MerCruiser. MerCruiser ...<br />www.mercurymarine.com/mercruiser3?search=1 [Found on Yahoo! Search]

 

[John_S]

Re: Will swapping 3.0 heads gain me a few HP?

In the Jan 06 Trailer Boats mag, there is blurb on the 3.0 MPI. Basicly it was delayed (again) because it was burning valves with the new redesigned intake/exhaust manifold. What is surprising, is that it states that it expected to be rated at 155hp! Says it might be introduced at the Miami International boat show in Feb.

 

[craze1cars]

Re: Will swapping 3.0 heads gain me a few HP?

Thanks, John. I guess we'll wait & see. Frankly I would expect more than a 10 HP increase over the carb'd version, so 155 wouldn't surprise me at all. When you compare rated HP #'s for every other carb vs. MPI in the Mercruiser lineup, the difference is between a 15 and 20 percent increase in rated HP.<br /><br />So if that follows, 135 should go up to 155 or 160 with the addition of a true MPI system. And for little extra weight. If cost is kept reasonable, this will be a HUGE improvement for entry-level boats, IMO. I just hope teasers become reality soon. The less carbs sold, the better for the environment as well.

 

[John_S]

Re: Will swapping 3.0 heads gain me a few HP?

If so, they could have gotten that HP awhile ago with just a larger 2-barrel carb and newer freer flowing intake/exhaust manifold. While the blurb says Merc is trying to fill the HP gap beween the current 3.0L and V6, I bet it has more to do with upcoming C.A.R.B / EPA restrictions. <br /><br />I for one, will not be happy when all the carbs will be gone. While you can't argue that it would't make things better, I believe there are bigger areas to focus on. In NY state, most of the the fish eating restrictions are from mercury, and environ impact from acid rain. Don't believe new restrictions on pleasure boats, will help that much. Opps, getting too much on the soapbox. Sorry.

 

[trog100]

Re: Will swapping 3.0 heads gain me a few HP?

we do know some "facts".. enough evidence hasnt been actually produced on this forum to convince those who dont want to be convinced.. but its all out there for those who wish to look for it.. <br /><br />fact one.. the 2.5 engine was discontinued in 1989.. <br />contribut<br />fact two.. the 2.5 engine was rated at 115 horse power at the prop..<br /><br />fact three.. between 1989 and 1994 there were two 3.0 engines.. the 3.0L rated at 115 horse power and the 3.0lx rated at 135 horse power..<br /><br />fact four.. the 3.0L engine (untill 94) was fitted with the same cylinderhead as used to be fitted to the discontinued 2.5 engine..<br /><br />fact five.. no other known difference between these two engines has been found except for the possibility that all the 3.0LX engines came fitted with electronic ignition as standard.. i would say they all did but its possible some still came with the points system as fitted to the 115 horse power 3.0L.. The "fact" is that no other differences have been found or pointed out by any forum members..<br /><br /><br />fact six.. there is no other evidence except the manufacturers claim that the actual power output of these two engines is 115 and 135 respectively..<br /><br />fact seven.. by some 3.0 jiggery-pokery merc managed to discontinue an engine without loseing their bottom end I/O 115 horse power option.. <br /><br />so we known some things that can be considered "facts" as opposed to just opinion..<br /><br />useing these things that can be considered "facts" everyone can now form their own opinions.. <br /><br />these things can be considered "facts" or at least beyong reasonable doubt cos the evidence is out there for anyone who is prepared to take the trouble to research it.. <br /><br />for those who cant be bothered.. they will just have to settle for the varied and confusing opinions of forum members..<br /><br />without wishing to offend.. this place really isnt the best place to find real imformation.. the internet in general and google is the best place for that..<br /><br />i never give "opinions" with being prepared to back them up by logical arguement or at least some "linked" back up evidence.. course if your face dosnt fit.. no matter how good your logical arguement is u lose.. he he he..<br /><br />my face.. at best.. only kinda half fits.. but my logical arguement is prety good thow.. he he he<br /><br />trog<br /><br />ps.. and if i have unduly influenced this thread/topic.. its for the one simple reason.. i really am the only contributor who has attempted to back up his "oppinion".. no one else has..<br /><br />and my "opinion" on this one is.. if u aint prepared to back up your opinion with at least some kind of logical arguement.. keep it to yourself..