*Cheap* Horse power Gains? Not Really

[Bubba1235]

I see many come to the forum asking if they can get significant H.P. gains cheaply. The answer in a word is, no. Swapping intakes and carbs might help in your street car but have almost no significant gain in a boating application. In fact, an additional 20 or 25 Horse Power in a boating application simply will not yield significant increases in low end torgue or top end speed for the vast majority of boats. If you want to see real gains you need 50+ H.P. to even notice the difference and that doesn't come from bolt on mods.

Can you get more H.P. from your existing engine? In most cases yes, but it really means pulling the engine and doing some major work. Different heads, different cam, having the engine borded, etc. Again, nothing easy or cheap.

Also keep in mind that in most cases the outdrive has a maximum H.P. limit and you REALLY need to check to make certain you don't exceed it. Also note that if you do build your existing engine it will almost certainly require a higher octane rating for gas and in todays world that means more money to fill up.

Point to all of this? Don't waste a bunch of dollars only to be disappointed in the results.

 

[John_S]

Re: *Cheap* Horse power Gains? Not Really

Most of the discussions here are on the mild side, 4brl/intakes, vortec heads, and mild cams. If you want to see money disappear, go to some of the go fast, boat forums.

The gains will be minor, compared to cars. If it is insignificant, it is up to the owners. Depending on a hull, stock motor upgrades, like I mentioned, would usually be in the range of 6-12hp needed for a 1mph wot increase. You do see torque increases through mid-band with 4brl and vortec head upgrades.

 

[John_S]

Re: *Cheap* Horse power Gains? Not Really

and if you don't change the cam at the same time you gain little.

Allot of people think that the roller cam is specific to the "vortec" engine. It is not, and was being used prior to the indroduction of the heads. Vortec heads work fine with the flat hyd marine cam.

 

[a70eliminator]

Re: *Cheap* Horse power Gains? Not Really

Bubba, that Winsor with right prop won't know if there are ten people or two people aboard, "horsepower smorshpower" torque is what you gives that feel of power. I have a 5.8 Cobra in a 20' open bow, with the 19p all-u-minum cheepie prop I can get 50MPH just me on the boat, and with two teenage daughters and two of their friends plus the wife I still get right around 50MPH.

 

[freak007]

Re: *Cheap* Horse power Gains? Not Really

"horsepower smorshpower" torque is what you gives that feel of power...

EXACTLY!!

 

[wca_tim]

Re: *Cheap* Horse power Gains? Not Really

I'm going to take a little different tack here...

if you find a half a dozen things that net 5 or more horsepower each, then chances are you're making enough difference to feel it in seat of the pants and see it on the throttle.

I might make the point that my 4.3 was pushing the boat as much as 10 mph faster than the one the previous owner trashed by running it with a cracked exhaust manifold. it wasn't a radical build. granted I typically spend a lot more on engines than a lot of folks do, but nothing like the offshore guys do...

think about it being nothing to drop 30 grand or more per engine... make it 2 or 3 for your boat... and then start looking at imco drives, etc... and the list just goes on - not a realm I'm every likely to be able to play in that's for sure.

what point am I trying to make with all the rambling?

I started off to say that even if you can't make a 50 mph boat into a 90 mph boat on any kind of a budget, the little things you do add up and can together make a nice difference - especially in seat of the pants mid-range torque, throttle response, etc... props nd set-up is obviously one of the biggest bangs for the buck here.

just my two cents...

 

[wca_tim]

Re: *Cheap* Horse power Gains? Not Really

Allot of people think that the roller cam is specific to the "vortec" engine. It is not, and was being used prior to the indroduction of the heads. Vortec heads work fine with the flat hyd marine cam.

Very good point, it is also worthwhile to note that roller cams have an advantage in terms of the lobe profile that can be employed without problems, but if you're talking about adding an aftermarket roller cam to a non-roller cam block to the tune of say a grand by the time you get done, your money would be far better spent on a good hydraulic cam and better heads...

roller cam is worth a few horsepower over a hydraulic (assuming you're cpecing the cam for a given engine build and can choose appropriately), but as long as you run oil with good anti-scuff properties / additive package (NOT automotive oil!) there's not that much advantage to running a roller cam at the rpm's we run in marine engines.

The primary reason that manufacturers switched to roller cams when they did was the epa / environmental impact driven phase-out of the oil additives that protected grey iron (ie. camshaft lobes) from wear. They needed a set-up that would handle the reduced anti-scuff properties of the mainstream auto oils of today...

I'm running a hydraulic cam in my 383(5) stroker motor... and while it's not built right to the ragged edge, its no slouch and spins right up to the 5500 rpm peak horsepower...

bottom line, say you had a grand or a little more to spend on internals after you accounted for a good intake, carb, spark arrestor and exhuast (gasp$$). On an older engine (pre roller cam being standard), buy vortec or better heads and a well matched hydraulic cam for the greatest gain in horsepower. Now that's putting a lot of cash into it and making major modifications, but you could see a huge gain in power if you played it right...

 

[QC]

Re: *Cheap* Horse power Gains? Not Really

"horsepower smorshpower" torque is what you gives that feel of power.

Maybe a better way to put this is higher peak torque will increase acceleration. HOWEVER, without more horsepower you will not go faster. Period. All of us have been suckered into believing that torque is "all that matters", this is incredibly false. You, your ownself, can make 400 lb/ft. torque, but I guarantee you cannot push your boat 50 MPH Also, the ONLY time you are employing full torque at ANY RPM is with the throttle 100% open. The fact is that high peak torque values are much more important to on road vehicles than boats, that's why marine engine manufacturers rarely publish torque values. Yes, a peak torque increase will yield a faster accelerating boat or allow you to plane with a higher pitch prop, BUT . . . the mods you make to increase torque will usually yield increased horsepower so that you can run that increased pitch out to WOT RPM hence gaining additional top speed.

Extremely misunderstood dynamics here, but the fact is you really cannot separate horsepower and torque as much as you want to, and especially in marine engines. You rarely if ever utilize the torque "hump" which, BTW, yields a horsepower "hump" allowing you to plane faster, or pull out a heavier skier, or plane a heavily loaded boat, but unless those things are a big deal, building marine engines to increase low RPM torque is not very helpful. Especially not to top speed . . .

HP = torque x RPM/5252 . . . One begets the other, but RPM matters, BIG TIME as it turns torque into horsepower, and despite what we all are told by those who do not completely understand this: you ain't goin' nowhere without horsepower . . . Sorry, pet peeve, and I am on a crusade to correct this egregious error

 

[mcleaves]

Re: *Cheap* Horse power Gains? Not Really

But you don't just "bolt on" torque. My point in this was that it makes little sense to start swapping Carbs, intake manifolds, expensive ignition sytems, etc. in trying to find another 10 or 20 H.P.

Hey Bubba,

While I think the meat of your assertions are reasonable, I think it depends a lot on the base application you start with. Adding 10-15 hp in 250hp base application may be negligible, but adding that same gain to a 115 hp engine will definitely yield some performance.

In my case I had an AQ125A 115 hp Volvo. Single carb, points based system. Swapped it over to a dual carb bolt on from one of the other Volvo 4 Cyl models and added electronic ignition. While I didn't dyno the engine, everyone else who had done these mods suggested it was about a 15-20 hp gain. It was VERY noticeable. Faster planing times, no need to move people around the boat as much, and about 4 mph to the top end. That is real world data. Torque or not, there was enough performance improvement to warrant the couple hundred bucks spent

As for boltons increasing torque. I am by far not an expert, but this is EXACTLY how VP increased HP in their AQ series 4 cyl lineup. Each step up in HP from model to model was either done by increased bore, adding a second carb or a combination of the two. Just reading the service manual will tell that much.

So I think it has more to do with how much gain you get given your base application, not just how much you get total. 10 hp on a 100 hp engine is, well, 10%. That's significant enough in most cases.. I just don't know what percentage becomes negligible. I also don't know if the improvement graph is linear. For instance is 20 hp on 200 is just as good as 10 hp on 100hp? It may be that you need 50 hp on 200 hp.

I just know it does work out in some cases, probably in the lower hp range where any improvement may be significant

M

 

[erikgreen]

Re: *Cheap* Horse power Gains? Not Really

You CAN actually bolt on torque... provided the bolts involved are the ones that mount the engine

My 2 cents worth on this is that if you're already having an engine rebuilt, then go ahead and put in the "performance" parts. But if you're looking for more power in any given boat, you can either replace the engine with a larger one that's still safe for that boat, or replace the boat.

That said, each situation is different. If your boat happens to have a 2 barrel carb and intake, then a four barrel will be a noticeable improvement. If you switch your carb and intake for a marine fuel injection system (salvaged from somewhere) you'll feel that too. Generally the rule of thumb is, unless it's going to get you 25% more horsepower and torque or similar, it's not worth doing, and it may cost as much as a new motor just to get that.

Erik

 

[cheburashka]

Re: *Cheap* Horse power Gains? Not Really

I'm going to take a little different tack here...

if you find a half a dozen things that net 5 or more horsepower each, then chances are you're making enough difference to feel it in seat of the pants and see it on the throttle.

The problem with this is that the horsepower gain is measured in comparison to a bone-stock engine. Increasing the efficiency of one system will increase your horsepower a lot, but there are diminishing returns with each new addition.

I used to see ads on Craigslist for things like stock Honda CRXs with 62HP engines, but the doofuses would add up the potential gain from each add-on--5HP for the "Nology Wires," 7HP for the cold air intake, 11HP for the "Vornado," 13HP for the coffee can exhaust tip, 15HP for the magnet on the fuel line, 28HP for the stickers and 45HP for the wing on the back. By the time they were done the car had more HP than a top fuel dragster, but would barely outperform the stock version.

 

[mtnrat]

Re: *Cheap* Horse power Gains? Not Really

The problem with this is that the horsepower gain is measured in comparison to a bone-stock engine. Increasing the efficiency of one system will increase your horsepower a lot, but there are diminishing returns with each new addition.

I used to see ads on Craigslist for things like stock Honda CRXs with 62HP engines, but the doofuses would add up the potential gain from each add-on--5HP for the "Nology Wires," 7HP for the cold air intake, 11HP for the "Vornado," 13HP for the coffee can exhaust tip, 15HP for the magnet on the fuel line, 28HP for the stickers and 45HP for the wing on the back. By the time they were done the car had more HP than a top fuel dragster, but would barely outperform the stock version.

LOL, that is great

 

[QC]

Re: *Cheap* Horse power Gains? Not Really

And in defense of your original contention Bubba, bore and cam would not be considered bolt on . . . even heads to most people . . .

 

[Limited-Time]

Re: *Cheap* Horse power Gains? Not Really

If you want Bolt on performance gains for your inboard or your IO...........................bolt on a blower.............

 

[Chris Hyde]

Re: *Cheap* Horse power Gains? Not Really

Most people fail to realize that horsepower is simply a derivative of torque, not the opposite.

 

[QC]

Re: *Cheap* Horse power Gains? Not Really

I agree, Chris, and the only reason I struggle with that statement is many people would see that as confirmation that torque is superior when ultimately it is the derivative that we all pursue . . .

I would prefer to say that horsepower is the repetition of torque as opposed to a derivative . . . This brings in the RPM . . . If efficiency was equal, I would rather have a 20,000 RPM engine with peak torque of 200 at 10,000 RPM, than a 5,000 RPM engine with peak torque of 400 at 2500 . . .

 

[mcleaves]

Re: *Cheap* Horse power Gains? Not Really

Torque or not, there was enough performance improvement to warrant the couple hundred bucks spent.

If you are lucky enough to find those parts for a couple hundred bucks you may be right. Buying new (or reman.) intakes, carbs, gaskets, etc. will usually run a lot more than that.

As I said that was my situation. On those VP 4 cyls, you can grab solex carbs for 50.00 and an intake for about the same. Pertronix makes the points conversion for about 100.00 last I checked.

I agree, it may not be economical, and I also question how much hp % increase you'll get doing this on a small block. Speaking for the VP AQ series 4 bangers it's very doable and cheap, IF you get used parts, which there are plenty of on ebay. The carbs are incredibly simple and a monkey and rebuild them and the kit is about 40.00.

I am just saying that there are places where this kind of upgrade makes sense. I won't argue with you on GM's or Fords

Each step up in HP from model to model was either done by increased bore, adding a second carb or a combination of the two. Just reading the service manual will tell that much.

Bore yes, different cams yes, better head design yes. Combine this with a better carb and you get more power. (In other words, lots more to it than just a carb change. Not to say a crb won't help, but its an expensive bolt on that gives a pretty small bang for the buck.

You can go to dougrussell.com and play with the parts lists. You'll find the head and the cams on all the OHC 4cyls will be the same part numbers. AQ120 - AQ140
Part # 1346408 for the heads
Part # 1336767 for the cams

VP did it in some cases with JUST adding a carb (not 2 to 4 barrel, but dual). In some cases they kept one carb and instead increased the bore. In some they did both. But the heads and camshafts are the same. But there is a clear path in their product line with just upgrading the carbs for HP

So you can get the benefit of increased HP on these engines buy going from 1-2 carbs, and the increase IS significant with respect to the % increase. Then going from points to electronic makes a big difference, but only if it's running properly to begin with

A lot of people try to solve performance problems by throwing upgrade parts at the problem when their timing/dwell, plugs cap etc are the issue. But that's another thread isn't it

M

 

[Mischief Managed]

Re: *Cheap* Horse power Gains? Not Really

Most people fail to realize that horsepower is simply a derivative of torque, not the opposite.

How much HP is 450 ft-lbs of torque at 0 RPM?

HP is absolute. It's a measurement of the ability to do work. Torque is just force. Without RPM figured in, torque is no more meaninful than dead weight on a lever. With RPM figured in, it means HP.

 

[QC]

Re: *Cheap* Horse power Gains? Not Really

It is nice to know that some people get it ^^^^

 

[45Auto]

Re: *Cheap* Horse power Gains? Not Really

LMAO - trying not to say anything -