Re: Supercharging 03' Merc 350 Magnum?
All,
Thanks for the great responses. Here goes:
1. I recognize that your engine is fuel injected, but will it calibrate to the 5500 foot elevation?
rob
- The boat runs fine and I really don't know the details of what the ECM is doing so I must assume it is adjusting to the elevation. When I picked the boat up in Wisconsin (elevation <1000') the top end was 50ish with 24 pitch props and stock gears. When I got it back to New Mexico (northern), I had the gears changed out to those recommended by boat shop for high altitude. Huge improvement but still had to go to 22 pitch to get any hole shot. Top end now ~35mph. The real performance concern is getting on plane so skiers don't drown before they get out of the water. There may also be a skier's skill factor here that would help too. However, this ol' fart knows his limits and more HP/torque will help!
2. My only real negative in this is that the stock 350 really is not built (lower end) for it and your engine life expectancy is going to take a serous hit.
- Agreed. What I expect is that I will end up pulling engine within next 2 years to put in the bullet proof bottom end. I've heard 1000 hrs is a good estimated life span for this engine (no data, just opinion) and I would expect these changes to cut that in roughly half. I'm ok with this in that I have 3 sons and we like to work on mechanical projects. The real concern I have is in the fuel injection and ECM functions since that is all black box magic to me. We can handle the wrench related activities. I really don't want to have the engine cover up all the time tweaking while on the water.
3. If you do, and you want it to last very long reliably, you're going to want to build the engine to take it. You're talking 3000+++ as a basic starting poin for the cheapest blower set-ups, and there are issues with getting the ecm reprogrammed reliably. (Most of the people I know that run blowers on marine small blocks, run carbs. Only have to lean it out once to have to start over again...)
Bottom line is that it would probably be a better use of time and money to build a naturally aspirated stroked small block with a fully forged bottom end, good heads, good aftermarket exhaust, etc... You can build a torque monster that'll still make over 400 horsepower, or more if you spend more and go to a 406, or even larger if you pony up for an aftermarket block...
I would also spend the effort and money to go with an experienced marine builder - Their experience is well worth the hassle of finding one or dealing with one that's not just down the street.
Where are you located? People might have some recommendations...
Just my two cents...
- You have nailed the debate on head. The Whipple kit is ~$7k so pricey is definitely the nature of this debate. However, a repower is $12-13k to get a Merc 6.2. I agree with you that the stroker path is viable but I'm concerned about what losing the reliability of FI and ECM (see earlier comment about tweaking on the water). I may be inexperienced in the dark arts of black box magic (ECM/ECU/etc.) but I know I like the performance and reliability I've gotten from this technology. Therein lies the debate over trade-offs.
4.At 5500' elevation and at 3 psi boost you are not going to be producing much more than the originally rated horsepower (if any). Personally, I think this would be a great addition given your boating elevation. I believe many boater at Lake Tahoe do this just for this reason.
You should probably consult with whippe technical support to see how much hp you are actually going to make at your elevation and keep it around the original 300 +/- hp and for sure keep it below 400 hp, since that's what the Bravo 3 is rated. Get some prices and go from there.
- Excellent points. I have contacted Whipple and they advise that with pulley change outs I can get sea level performance (300hp) and more if wanted. Real attraction of their system is the reprogrammed ECM. They are quite proud of their system and from what I've read the public agrees that they put out a high quality product. I'm interested to hear what others at elevation have done (like Lake Tahoe). I'm really not interested in tearing up the water so staying below 400hp is no problem and if I could get back to 300hp/+torque at this elevation I'd probably be happy.
Your responses are a big help. Does anyone know what the original torque rating of the 350 Magnum is? I've looked online and Merc only lists HP. GM lists torque ratings but not sure which engine type Merc. used to produce their version of the 350 Magnum. I've heard the rule of thumb for HP loss with elevation is ~3% per 1000' so, if true, I lose ~16.5% or ~50hp. Does the torque change at the same rate? Thanks again for all the good input.
Gary
