Supercharger 1996 5.0

"I have a 98' Larson 226 SEI with a volvo penta 5.0 in it. I mainly run my boat at one of the higher elevation lakes, at around 5500'. The boat runs fine at the lower lakes, but obviously I lose some power at the higher altitudes. I was kicking around the idea of adding either a whipple or a centrifgal supercharger to it. I wouldn't over drive it too much and would be looking at staying under 5 lbs of boost. The only problem I have is I am unfamiliar with the GM MEFI ECU's that are used on the engine. I have found almost no info on this type of application on general google searches. The initial idea I had was possibly going with larger injectors and modding my fuel map. I did see though that the MEFI units do not use the standard OBD2 ports. I found the software and MEFI connector for a laptop for $650. Kind of pricey for a single tune. Does the marine TBI units use the stock GM TBI injectors? I have not had time to look at my existing set up since I have the boat winterized right now. Does the marine TBI unit use the GM 40 pph injectors found on the vehicle 5.0/305ci engines? Just looking for some general info and has anyone tried supercharging with the TBI's and modding the MEFI ECU's?"

"Marvin,

I love the benefit

"Marvin,

I love the benefits of a supercharger in the fact that you can get better fuel economy,lots more low end torque and its very reliable. All that being said, i was talking about the automotive world.Marine is a whole different ballgame!!!A supercharger in a boat can be a nightmare as they are not gonna be very reliable,cause outdrive problems, and your gonna have more "wrench turning" time IMO.......By the time you buy a supercharger,injectors,ECU upgrade,install,reprogram,etc.........you could buy a NEW 350 5.7L with either EFI or Carb versions avail. ranging from 280-350HP!!!!That will be a easy swap and will be alot more reliable and trouble free down the road.Once again this all my own opinion.....Either way you go the HP difference will make you change the gears in your outdrive to the proper ratio...Good luck"

"Marvin, Great idea for auto u

"Marvin, Great idea for auto use, not a great idea for marine use given what you'd have to engineer to make it safe and practical with any type of return.

Are you now running an SP or DP drive?

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"SP right now. All my experien

"SP right now. All my experience is in the auto world. I have been building racing engines most of my life and I just thought it may be feasible. What got my wheels turning was I am building a 410" donovan sbc with brodix -12 heads and adapting an 8-71 to it, so I have blowers on the brain right now I guess. I was just looking for a very mild boost to compensate for the altitude difference. Building a 350 would not be a problem at all since I probably have most of the parts laying around the shop already. I was just kicking it around in my noggin "

"OK, if SP now, consider the D

"OK, if SP now, consider the Duo Prop lower unit addition to your existing drive!
At sea level, and on certain hulls, the DP is similar to adding 80-90 horse power. Much better bang for the buck, IMO.
However, I can not tell you for sure about higher altitude use.... but it would still be an improvement!

And if you were to build a 5.7L marine..... there will be definite does/don'ts to make good marine horse power.
I'd suggest learning how to compliment the automotive knowledge with the more true sense of what is required for marine.

."

"Classically, hi altitude oper

"Classically, hi altitude operation ( non aero) issues were resolved by changing the jets in a carbed engine. I guess with an ECU, you'd need to change the ROM... if they are even accessable in a marine ECU. When last I looked a blowers, Paxton at least seemed to use an enrichment injector/jet to get around the ROM mapping issue.
I spent many year driving belt driver superchargers on the street... Initially in a 1957 Stude Hawk ( I "modified" that blower), and then for many years in 63 Avanti ( both the stock R2 engine and then one of Granatelli's leftover handbuilt/blueprinted R3s.
Mucho fun... improved gas economy at cruise, but if you stepped on it you could literally watch the gas gauge drop."

"I am assuming that there is a

"I am assuming that there is an O2 sensor in the exhaust to compensate for the air/fuel ratio change at altitude since it doesnt load up or seem to run rich. Its the lack of usable air at a mile high that is killing my power. I too have seen the "piggyback" injector jet, but it seems that has gone the way of the dodo bird. I have found the software and 10 pin patch cord to program the MEFI units 1-4b, but at an extra $650 for a one time tune, just didnt seem like it was worth it and figured I could find someone local that might be able to remap my fuel curve. Again, this was just something I was tossing around and wanted to see what input you guys had. I am the type of person that does lots of research before I ever move ahead on something. I am now leaning on an engine swap to a 350. I have a long standing relationship with comp cams and would probably talk to one of their techs for a good marine cam selection for my particular application, since my own cam selection software only covers vehicles. Unfortunately, I wouldnt have time to get an engine together before this summer due to prior committments to building other engines for guys that will keep me busy for several more months. I may just opt for a prop change and stay out of the lower lakes so I can keep my rpm's down at wot. Best of my recollection I have a 14 1/2-21 3 blade alum on it now. I lose about 500 rpm at the higher lake. I think its 200rpm per numerical blade change, does my memory serve me correct? Do they make a 19? I havent scrounged around yet for props, but I may get to it tonight. Thanks for all the input guys."

"Seems like we're getting

"Seems like we're getting into comparisons between automotive and marine use here that may not be logical, IMO.
Fun stuff, but isn't this a Marine related forum? LOL

That being said, for any of us operating at higher altitudes, we just simply must understand that there are sacrifices in doing so.
Boosting air intake would certainly help..... but look at what would be required in doing so.... and in doing so safely and in a way that would conform to regs!

Seems to me that if this is an insurmountable issue, a re-power or the Duo Prop would be much more logical and cost effective in the over-all scope of things!

Just my two cents!

."

"Just a thought. If the boat h

"Just a thought. If the boat has plenty of power at sea level, then just boost it to sea level pressure, no mod to fuel delivery system required. It's common in aircraft using a turbocharger, called turbo-normalised."

"Chris, that was kind of my or

"Chris, that was kind of my original thoughts, by keeping it at a target boost level of 3 or so psi. Procharger claims that their marine units under 7 psi do not require any mods to the ECU for fuel, but I have a hard time believing that one. I can see 3-3.5 being borderline in my mind.
Ricardo, unless I am not seeing or understanding the duo prop set up, I don't see how that is any less expensive than what I am looking at. The duo props are around $1300 and you have to change your lower outdrive correct? I was told it was a $3k change over for everything, is this true? I have almost no knowledge of a duo prop setup and how they work. Info and ballpark pricing?
For comparison, I have a friend with a complete whipple TBI setup that will let me have it for $1000 and add programming, doesnt even come close to $3k. Setting aside the reliability issues you guys have mentioned. I am curious though, what is the difference in issues to address as far as reliability in marine vs. a vehicle? I am not trying to be thick about it, just am having a hard time with that after much thought. Thanks again for everyone's help on the subject."

"The Golden Hawk, from the fac

"The Golden Hawk, from the factory was set up at well under 5 psi... something in the range of the 3 psi you are talking about. I had a belt failure once and drove the car sans belt, i.e., sans blower for a week. Very noticeable difference. The "Mod" that I did to the blower involved me finding how Paxton set the boost for different CID engines. I upped boost to 6-7 psi max. BIG difference. I had to go to an electric fuel pump as I was getting starvation at high boost/rpm combos...Why combos.. That vintage Paxton had a variable, demand sensitive boost drive ratio feature. I think that 3 psi will more than compensate for the loss "at altitude"."

there is a place that sells me

there is a place that sells mefi 1-4 computer re-flashes

the computer program is 1800!!!

"Guys, Can I jump in and ask a

"Guys, Can I jump in and ask a question,,Are you saying that if I change my SX drive to a Duoprop I could in-fact be adding 80-90 horse power @ the prop???"

"Bert, I am a bit in the dark

"Bert, I am a bit in the dark on the duo prop set up, but I have read that you get a lot more out of the hole but lose a little bit of top end due to parasitic loss. I also do not completely grasp the process of the change over and what it consists of. I have been told conflicting things from the advantages of the duo prop. Local guy tells me that it may not be the option for me since I am underpowered at altitude already. I think I will just make a prop change for this summer and do alot more research before I move ahead on anything "

"Bert and Marvin....., Forgive

"Bert and Marvin....., Forgive me .... and let me add some clarity to that earlier comment!
Quote:"At sea level, and on certain hulls, the DP is similar to adding 80-90 horse power. Much better bang for the buck, IMO."
There is no hard data to support 80-90 HP gain at the prop.
It was an example only saying <font color=""0000ff"">"similar to adding 80-90 horse power"</font> as to compare what I've seen when going from a 5.0L to a 5.7L (for example) yet staying with a single prop drive.
The Duo Prop suggests more performance improvement over that of what the larger 5.7L w/ single prop drive may gain us.
Volvo's 1983 literature suggested a gain in economy and performance of 25-30% if memory serves me.

I've installed these on my own boat, my son's boat, his friend's boat and on customer boats........... all but one (and we don't quite know why) showed quite an improvement.



As a comparison:
On my own 28' SDN F/B twin engine boat, the difference was night and day.... both in reduced planing distance, more top speed, more ability to be up on step (and then some) and ability to remain on step at a lower engine rpm.
The boat previously struggled to get on step with the single prop drives (and this is w/ two new 5.7L engines)
Now with the Duo Prop drives, it comes up in a very short distance..... and acts as though it is not working as hard to remain there.

We did one to my son's 24' SDN F/B boat..... the gain was well worth it!
We also did one to boat which belonged to a friend of my son's.... of which was also a 24' SDN F/B boat..... again, tremendous gain. It was all that boat could do to get on step with the sp drive.

It would be very involved for me to take the time to river run each boat and collect before/after actual data.



I also participate on a boating forum where many members have done the Duo Prop upgrade! Some were to SDN F/B's.... some were to Single Station models......... all with very positive results. In fact, I don't recall reading where any one was disappointed.... and there have been several long threads about this topic.

I helped one man convert a 460 OMC KC drive to a complete DP C drive. This was in a 28' single station boat! Of course he had to do a complete installation to go with an AQ series drive.
He is also extremely happy with the improvement.


Here is a reverse engineered scenario for you:
<font color=""0000ff"">Short story...
I owned a little 24' SDN F/B.
Heavy... but a fun little boat.
Engine was a 200 HP 5.0L
I installed a Duo Prop drive and used it in the interim while I was finishing the 28'.
The boat surprisingly scooted right along @ 37/38 mph tops with the Duo Prop.
I removed the DP to sell the boat w/ a single prop.
I had never operated this boat without the DP.
Went for a river test.
It was all that boat would do to get out of it's own way w/out the DP.
I don't believe that a 5.7L would have helped this hull like the DP did!
I was lucky that I found a buyer who was OK with the performance!</font>

So, with all of that being said...... I can only suggest that going from a 5.0L to a 5.7L (while staying with single prop) would not render as much gain as though you added the Duo Prop to the 5.0L!


I am also not able to comment with any experience as to the gain for high altitude use. I would speculate that there would still be an improvement!

Keep in mind that the Volvo Duo Prop does not perform as well as the BIII will at speeds above 40/45 mph.... but does better than the BIII at speeds below this. This has to do with the pattented propeller design.
."

"Thanks for some clarification

"Thanks for some clarification and info Ricardo, it helped alot. I honestly had no idea that they made that big of a difference. I may do a little shopping around and get some ball park pricing."

Duo props basically work by re

Duo props basically work by reducing "slippage". I suspect that if your engine won't produce enough torque at altitude to spin your existing prop to sea level WOT levels that a DuoProp may not solve your problem to your satisfaction.

The RPMS that an engine attains at WOT is that speed that produces the torque that the prop load presents. It's a balancing act... A particular prop ( D x P) needs so many foot-lbs of torque to spin at a particular RPM and the engine will rev to that torque point. That's why an engine in neutral will rev until it self destructs ( or the valves float for hydraulic lifter engines or the smart ignition cuts off) but only attain a particular RPM in gear.

"I can't suggest with any

"I can't suggest with any certainty that the DP will cure this altitude issue.
Currently the engine at high altitude is not producing enough horse power nor torque to move the boat at speeds that can be achieved at or close to sea level.

If at altitude, the existing engine will not move the boat at speeds desired, then the Duo Prop may take what power is available and more efficiently apply it in the form of more thrust.
(you'd have to understand the technology behind Volvo's patented Duo Prop propeller design.)

Like said in my above post, the Duo Prop, in certain hulls, will generally out perform the single prop by 25/30% at (or close to) sea level.
This is documented data.... not a guesstimate. Unless one has experienced the improvement, one would be unable to adequately comment!

Is it worth a try for high altitude improvement???...... I don't know!!!
Much would depend on one's budget and/or what one could pick one up for.

."