Knot 4 Me

Not arguing with anyone. Just stating what I was told and pointing out there is conflicting information out there on the topic. And yes, it was the debut of the 525 where this topic came up for discussion at a manufacture's rally where I was speaking with the Merc rep.

onesickpantera

I agree it is confusing as it does seem reversed. As Bob's dyno numbers point out the black motor numbers are always low.

Anyway I am taking this thread off topic so carry on.

Raylar

Obvoiusly there is so much conflicting information on what all Mercury engines make in HP at the crankshaft and at the prop and the mis-information that comes even from Merc marketing materials, sales reps versus Merc Racing techs, etc. that I think its worth saying that this is really a moving target and the only for approximate reference and marketing.
Raylar as an engine builder is always conservative on our horsepower ratings on our kits and engines and we do measure only at the crankshaft, using SAE J-1349 specs and with water exit in the exhaust headers on a fully calibrated dyno with full corrections to try to create a HP condition that the customer will usually achieve in the boat with a proper installation and similar conditions.
I realize that many builders and shops do not always have the ability or equipment to dyno test in the exact same fashion.
Besides this, we can always assume that no two dynos will test the same exact numbers even with corrections and sometimes an engine will vary from one pull to the next on the same day on the same dyno sometimes only minutes apart.

In any event, back to the real thread inception question and request. As a fairly knowledgeable engine builder I will reaffirm the statement: "Engines are really just air pumps that are burning fuel to make horspower and torque" To properly and efficiently add power and torque to an exisitng engine design or state of original engine specs. and build it is imperative to look at three simple aspects to get the best efficiency and power and torque production. One is air in either pulled or pushed from normal aspiration or boosted input. Two, the compression of the fuel and air charges with their subsequent ignition and burn and Three the exit of spent burned air and fuel mixture (exhaust) thru the exhaust.
A good and general way to achieve this measurement of an engines efficiency as an air pump is to measure and calculate the engines volumetric efficiency at various rpms and load to establish this efficiency.
Generally the higher the volumetric efficiency (air pumping efficiency) at various rpms the higher the power (HP) and torque that may be produced at those rpms.
This is why it is so important to look at a lot of variables in increasing power and torque in an engine thru rework or upgrades. Simply, if one does not have an efficient intake system, and efficient air/fuel cylinder filling and combustion system and an efficient exhaust system, all three being created in the best equality and balance the engines overall efficency and power output will not be optimized.
What this tends to mean for the average performance boater, novice and professional engine builder is that you cannot just put a a selection of various intake configurations, camshaft specs., cylinder head types and configurations and exhaust configurations and end up with the even good or better power and torque production without a lot of good testing and verification to achieve the best results.
This is why we really use the dyno. As a test only tool and not as a solution for the goal of best efficiency and power production.

Back to the HP500 or for that matter any 4 cycle BBC V-8 engine as discussed here.
I as many professional engine builders in this industry hear and see all the time is that many times because of condition of the starting engines, budget of the customer and the need from the new engine configuration many customers want to stage or add upgrades or rework in stages. They will only want to add a new intake system and exhaust system at this point or change a camshaft only, or make other block increases in cubic inches or compression at one time an expect better or best results! Most of the time this is the wrong approach and generally results will be much lower improvements than if they or the builder took the approach that all these three systems have profound effect on each other and the ultimate increases will be how well this overall efficiency in these simple three systems work well with one another to give the final result.
This is somewhat well exampled by Eddie's results when his customer or his choices resulted in less than expected or poor results from trying to mix and the subsequent mismatch of intakes, head specs and sizes and possible exhaust differences . Eddie was using the dyno as a tool to identify what the combination would actually produce and found out that these choices were not well matched for overall efficiency and power production, hence the combo became a "pig" and serious "underachiever."
The HP500 base engine platform as produced by Mercury Racing can and does respond with additional power and torque when the total of these three systems is increased in efficiency and size increases. You just cannot make an across the board upgrade reccommendation without stressing and applying the overall efficiency model to the upgrade or rework.

If an HP500 engine receives good upgrades and choices in intake changes or improvements, cylinder head improvements thru rework or replacement, possiblecamshaft changes and potential exhaust improvements it nis very possible and not to hard to get this engine in a size between 502 -530 cubic inches up to a 600HP crankshaft output in a normally aspirated configuration. This is a 1.14 to 1.2 horsepower per cubic inch ratio and if overall efficencies are improved with these most or all of these three areas it is very reachable.
What does your HP500 need? A carefull blend of improved intake air flow( very critical in HP-efi engines as the stock intake and throttlebodies can and will become a limiting factor), improved cylinder head flow in all lift ranges from either well massaged stock iron heads, new iron or aluminum heads and potential compression increases from the use of aluminum head,improved camshaft profiles (in terms of valve event timing and some lift changes,) and potential exhaust system improvements (and that can mean in the header used and from the header back to the outlet also) Obviously good accurate ECM re-tuning and fuel system modifications will be needed to support this higher power level.
And again don't live by power (HP )alone, the additions to torque and where in the rpm bands these torque increases can be made will have a profound effect on how these power increases are really seen in the added performance of the actual boat! Remember that torque is what makes the prop keep turning and for the most part how much addtional pitch you can carry with the new added power at that rpm! I feel in boating with propellor driven boats torque is really more important to consider in most recrational uses and how and where it occurs than just talking about peak HP numbers!
And lastly keep the phrase in the headlights "There Is No Replacement for Displacement" in an average rpm N/A recreational use BBC engine. If you are reworking the engine with new internals and budget will allow ,use addtional bore first and stroke second to gain any reasonable increase in cubic inches as this is somewhat free power and torque when you are buying things like pistons and such! Just make sure the added air flow needed to support more cubic inches is supported by efficencies in all those three parts of the Air Pump!
This post will probably bore the hell out of most readers and I know I can be a wordie! I have always tried to never stop reading , listening and learning from those who might be more knowledgable than me! No one knows everything and I don't know nearly enough!
Never stop trying to improve! it makes everything better!

Best Regards,
Ray @ Raylar

Knot 4 Me

To the OP's question, Brad Smith of Smith Power in Joplin, Mo worked a pair of 2003 500EFI's for a friend of mine this spring. Dyno'd right at 600 HP. You could contact Brad to get the details of the build and how the motors were dyno'd.

frontline

guys thanks a lot for all of the info I have received on this thread!!!it will be instumental on my build !!!

onesickpantera

I would love to see that comparison just out of curiosity.

Is the higher hp using dry exhaust because no water is being mixed with the exhaust gasses, or because the automotive style headers have longer primaries? Or a combo of both?

Raylar

Raylar, as Bob at Full Throttle and others builders who have run engines like this on the dyno's with both dry dyno header exhaust, dry marine header exhaust with tails and marine headers with tails and full wet exhaust, we all have pretty much seen about 25-30HP less with a wet marine exhaust versus dyno headers and the dry marine exhausts with tails still tend to make about 10HP less than long tube dyno headers. This is caused by the fact that it is harder for an engine to pump exhaust gases out when they are full of water and water vapor as this mixture is heavier than just dry exhaust gas and there is more friction in the collectors and tips from the water on the surface of the tubes and tips.
This obviously is on normally aspirated engines of mild builds and does not apply equally to supercharged or turbo equipped engines.

Best Regards,
Ray @ Raylar

onesickpantera

So when comparing marine exhaust systems(wet and dry) to dry dyno headers you usually find:

Dry marine exhaust: -10hp
Wet marine exhaust: -25 to 30hp

Raylar

YES, thats what we tend to find.

Best Regards,
Ray @ Raylar

onesickpantera

So, basically you lose 15-20hp doing from a marine dry to a marine wet. So, does that transfer into the real world? Meaning would you see a 15-20hp increase going from full wet exhaust to dry or close to dry?

Most people go dry or close to dry because of reversion from big cams. But is there power to be picked up as well on engines that do not require dry exhaust because of reversion?

In realty I know it's not worth it to most to go to dry exhaust for 15-20hp. The cost and noise wouldn't be worth it to me. I am just curious if someone did want to if they would see a 10-15hp increase.