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Rootsy
08-17-2001, 08:25 AM
Alrighty Ladies and Gentlemen,

I'd like your opinions on the most bang for the buck to coax a bit more speed out the little 16 without breaking the bank (i know some of ya live for this!). i'd love to see low 60's without having to trim her out so far that she feels like she's a gymnist... Not talking about pullin the 350 and building some balls to the wall stroker or anything. You know.. exhaust, camshaft, etc etc etc... have a stock 350, roller motor, 1.6 ratio rockers, 4V and K&N, 21P Mirage, TBolt IV 350 Mag 22 degree ignition module, thru hulls... I was told by a few dealers that this long block is the same one they use to build the 300 hp motors, i just dont know what they did to take away 90 hp (retard or advance the cam a few degrees??? besides ignition and 2V???) cause i don't think i've gotten that back yet... maybe half... I'm open to all kinds of suggestions and opinions... so feel free to let em fly eh... i'm sittin at just a click under 59 mph @ 4500 rpm...

THANK YA! (as always!)

Root

BRIAN73
08-17-2001, 08:49 AM
I KNOW YOU DON'T WANT TO GO OVERBOARD, BUT I HAVE ONE THING TO SAY TO YOU "HEADS". FOR 8 OR 9 BILLS YOU WILL GAIN CLOSE TO 80HP ON A GOOD SET OF IRON SPORTSMAN 2 HEADS. I HAVE THEM ON MY 350, IN A 16. PUSHING AROUND 365 WITHOUT STROKING.
GOOD LUCK.

PaulO
08-17-2001, 09:32 AM
2 things:
What makes you think you are not at 300HP? What year motor are we talking about? The old 300 tempests were rated at the crank and the later 260s at the prop. Basically the same HP. New 300s are fuel injected, electronically managed and I don't know how much was changed internally.

Anyway, invest a couple of hundred in a different prop first. You are a little out of the real powerband at 4500 RPM. Lose some pitch and/or diameter and get the revs up to 5000-5100 or, better yet, have your prop labbed. You could also try a different style prop. The mirage is good, the right mirage plus is better but you may benefit from a laserII which is similar in design but has thinner blades.
PaulO

Moody Blu'
08-17-2001, 09:35 AM
yeah, I have a set of heads sitting in my shed, which I have been thinking about sending out to my freind down in tuckerton new jersey.
heads will give you the biggest boost definately.
If your looking for little bits of rpms here and there.
try buying a new distributor with a mechanical advance(MSD)-they make a distributor that has a total of 30 degrees-with the right cam bushing installed-thats what I have.
that should give you like 200-500 rpms more.

You could also do what big grizzly does and buy a closed coolling system for your boat and run your engine at 195 degrees.
closed cooling is a very WISE bang for your buck. you get a little more weight :(, an engine that will last for 10-20 years :) and 10-25 extra horsepower :D. kits range from 300-700 buckaroos.

or you could do one thing, ADD NITROUS :eek:
there is my 2 cents

Woodsy
08-17-2001, 09:45 AM
You need to decide how much your budget is and go from there... the cheapest way is to play with your prop selection like Paul O wrote. Once you get up into the 4800-4900 rpm range (I think 5000-5100 RPM is too high)then go have that prop labbed... you should be seeing an extra 3-5mph just by getting some rpm out of your motor and using a lab finished prop. This will cost about $700-$900.

If you want serious HP, go the camshaft & heads route. But this will cost about $1200 to $1500 to do it right. maybe a little more if you add roller rockers etc. After you mod the engine, you will be looking at a new prop so tack on another $500 or $800 if you have the prop lab finished.

Dave

Riley
08-17-2001, 09:57 AM
Jamie, great post! I may be a little off the wall in my thinking, but I've really become a believer in the Vortec heads. I think you could put a new set of Vortec heads, an Edelbrock Performer or Performer RPM intake, and a matched cam in your engine for under $1000.

However, I think you should keep in mind that the more power you shove thru that Alpha, the quicker it will expire.

RickSE
08-17-2001, 10:01 AM
Jaroot,
Hopefully soon, I will be trying a little experiment. I'm planning on removing the entire ignition from my drag car and running it in the boat, to see what gains I can make. The ignition consists of a Mallory Unilite dist. High Fire coil & MSD 6T ignition box. With this I'll be able to run any timing and advance I want. I'm hoping I can get more top end out of the motor with better spark and timing.

Also, I agree about the heads. Performance heads are relatively cheap and can provide some good H.P. gains over stock heads. If I go that route I'll go with aluminum Dart Pro-1 heads.

The other thing I've considered is a Holley/B&M 144 blower. It should fit under the hatch on an 18 but I'm not sure about a 16.

Jamesbon
08-17-2001, 10:09 AM
Heads are probably the best "b.f.t.b." If you go with a set of Vortecs, I highly recommend the GM Fast Burn aluminums. Had'em and they were very healthy.

Rootsy
08-17-2001, 11:42 AM
had a 19 Vengence on the boat up until i replaced the ignition module and i was barely getting 5K out of the motor at 55 mph, put the 21 mirage on which is also larger in diameter and dropped 500 rpm and picked up about 4 1/2 mph. according to a prop calculator i am at about 12% slip. I've been told that this is the same long block used on the 300 hp 350 Mag carb motors, motor is a 96 originally 210 hp 2V roller camshaft. and the operating range is 4200 - 4600 rpm. If i go heads i might as well go camshaft to take advantage of em. go heads and camshaft might as well add exhaust to get rid of it all... i'd be content in the 300 to 325 range, i'm not too tough on the alpha and i've watched em stand up to a big block for a number of years without issue. don't do much catching air and harsh reentries. i'd just like to get up into the low 60's for top end... more playing than anything... and i thank ya for the ideas.. go ahead and keep em comin!

Forrest
08-17-2001, 01:56 PM
I wouldn't bother with doing heads alone, without upgrades to the cam, intake, exhaust, ignition, etc. Actually, I think that a blower would provide the most reliable HP boost to a stock engine . . . but then again, you may have enough HP as it is now. The big problem with the 16 Donzi with a small-block V-8 is that the boat is too short for the amount of weight in the stern. The Ford 302 setup is a little bit lighter than the Chevy V-8 setup, and the V-6 setups is lighter still. You can try different props and you may have some success, but what I have found is that bow lifting props for the 16 are not the answer. I've actually had the best results using a clever (stern lifting) prop on the Mercruiser powered 16 Donzi. The best results on a 16 will occur when the X-dimension is raised a couple of inches and some weight is removed from the engine compartment. If you can find an Alpha SS, then buy it. That will fix the X-dimension problem. Othewise, concentrate on loosing weight in the stern. An aluminum intake and exhaust system will be like tossing a Florida State Linebacker out of the back of back of the boat. That alone will be a better investment than a bunch of bolt-on engine mods that may kill your engine reliability.

Moody Blu'
08-17-2001, 03:53 PM
that msd 6t ignition is what I run, its great!
that along with the msd distributor is a trick set up since you can connect the distributor to the ignition.
the 6t is great since you can put a rev control unit into it, ( i have one) it has a 7000 rpm chip so if the boat ever gets airborn and I dont lift off the throttle for some strange reason, the motor wont blow.( I want to put a 6000-6500 chip in there but not worried about that right now.
just go for the nitrous :P

Greg
08-17-2001, 04:44 PM
Sounds like your motor is already pretty healthy. Although the need for speed is always there. The book Small Block Chevy Marine Performance by Dennis Moore is a good reference and starting point. You may already have most of what you need in there and just couple of parts and a tweak or two will put you where you want to be.

Rootsy
08-17-2001, 06:48 PM
Yep I have Dennis Moore's book, tells me some stuff that i've wondered about as far as ignition and what's stuffed inside. I've replaced the cast iron 2V with an Edelbrock Performer and 600 holley, 1.6 ratio comp cams roller rockers and an ignition module from the 350 Mag Carbed motor so i can get into the 30 to 34 degrees of advance range (32 at the moment). Really i wonder what kind of HP it takes to turn a 21 Mirage @ 4500 RPM in a 2700 lb boat. I would venture to guess atleast 250 @ the prop. I'd go MSD but i'd rather wait til i really need to fire stuff in the cylinders. If i go camshaft and exhaust i'll probably toss a pro billet and box in, plus rev limiter (WARM FUZZY FEELING)... what do you guys suggest for a good all around camshaft? AND Sky Blue by LAW you need the Marine pro billet dist. and 6M2 box... plus why run the rev limiter 2000 rpm higher than your motor ever sees... 7000 rpm for a hydraulic cam is reaching dangerous territory. at 7000 i can almost assure you that you'll float the valves (unless you have GOOD anti pump up hydraulics)... actually for any non balanced, stock rod, cast crank motor 7000 rpm is PUSHING IT... I'd be goin 6000 max, or 500 rpm above max rpm...

as always.. more power is nice as long as you can put it to the ground... err WATER...never really considered a cleaver... actually i have very little experience with them. with the mirage i trim it out and i feel like the whole boat is out of the water.. MUCHO LIFT! i see your point forrest, bout stern lift... i can turn 4300 -4400 with the trim all the way in and the nose down... keeps things stable too.

Gearhead99
08-17-2001, 08:34 PM
Cheap, easy HP is NOS. Sure you can't run it long, but it will kick your Donzi in the butt when it comes on.

Formula Jr
08-18-2001, 03:14 AM
The absolute cheapest speed modification you can make, is to start running in rougher water with your Donzi as is, and then buying a second back water boat - like a Magnum Missile with a 200 HP Merc. OB ;)

Riley
08-18-2001, 08:32 AM
Jamie, I've been giving some thought to your comments regarding your power output, in relation to your engines rated power from Mercruiser.

Way back in the late 50's Chevy came out with the fuel injected 283 in the Vette, which was given a higher power rating that the carb equipped 283. Truth be told, the carb version would run with, (and often outrun!) the fuelie motor. And the carb engine costs hundreds of dollars less than the fuelie. Smokey Yunick had a great story in Circle Track several years ago telling the whole story. Bottom line is that Chevy had to rate the fuelie higher than the carb version to move those first units through the dealerships.

It's possible Mercruiser could have done something similar with your engine, rating it at only 210 hp. Why is my 305 rated at 220 hp, with the only difference being the Vortec heads? I think Mercruiser had to do away with the 4bbl versions of the 350 Mag, going with the 2 bbl or the fuel injected engines, because the 4bbl 350 might have been just a tick slower than the fuel injected engine, but cost thousands less. There wasn't enough difference in performance between the 4bbl and fuel injected versions of the 350 to justify the higher costs to the consumer.

Okay, I know, I'm rambling. My point here is that I'd bet your stock engine was somewhere in the 225 to 240 area, and you are now getting 275+ out of her.

Can any body on here verify or refute the idea of the cost/performance of the 4bbl 350 vs. the fuelie 350 had anything to do with the demise of the carbed 350 Mag? I'd be interested in knowing the story.

Rootsy
08-18-2001, 09:06 AM
i've wondered about my motors rated output. first of all Rick had his dealings with the donzi factory with his 210 350 which was actually somewhere in the 240 range @ almost 4000 feet above sea level. I spoke wiht my local donzi dealer recently and they said it was 210 and that the boat i have is rare because in 97 mercury ran out of 305's so they put 350's in and whether they modified or just restated numbers they needed something in the 305 power range. i'm still scratchin me head on that one...

BigGrizzly
08-18-2001, 08:33 PM
Here is the ordre in which to go. You already have the Four barrel carb. so do it this way its the cheepest and easiest.
1) Prop it , the marage plus isn't the only prop around, I don't use it on my boats anymore,
2) Cam it, Heads are useless without a good cam. The cam is the real heart of the engine.Don't get sucked in to a bottom/midrange cam they are useless in a boat.
3) A good exhaust system not just thru-hull.
4) heads -- make sure they are compatible with the pistons, or your in trouble. I f your thinking of spinning it more than 5300 rpms then better build a good bottom end.
One word of advice---Never make more then one change at a time. Such as a prop and carb, or change timming and a carb.

Randy

Rootsy
08-18-2001, 08:53 PM
i agree with your thinkin there Randy. you have the fundamentals of trouble shooting and problem solving down pat there eh! have the carb dialed in well and i've done a prop to get the rpm's down... hey the price was right... now i'm playing with ignition timing... see what i can get out of it and then go play with props more a little later. Soooo what do you boys suggest for props on the 16 with a V8 sittin under the hatch? I'd whip a camshaft in her in a second BUT... gettin the motor out is almost more work than it's worth at the moment... maybe in the spring!!! i'd like to see 5K max out of the motor... all depends on if i go with a new cam and where it makes peak HP... with the camshaft that's in it once you pass 4600 - 4800 she just struggles to gain anymore rpm... with the 19 vengence i could spin it instantly to 4600 or so and it'd slowly creep from there up to 5000... with the mirage it's quick to about 4400 and wiht a bit of trim 4500 solid... think we;ll keep tweakin for a bit and we'll see where we get eh!!!!

thanks for all the advice!

Sam
08-19-2001, 02:11 PM
jaroot, we have got to get together, I have what I think is a stock 350 2bl in my 16. turning a 21" Stelitto I run 56-57 mph(gps) @43500 to 4400. I to am looking for that 60mph mark. The first thing I did was play with props a bit. I went from a 19" to the 21" and picked up 2 mph. I have a K&N air filter on order so the jury is out on that yet. I would be willing to meet you some time during the week. I live in Plymouth so Monroe is a short poke down 275 for me. Give me a shout so we can look at our calenders.

Sam

Rootsy
08-19-2001, 03:34 PM
Sam,

actually i live in the irish hills bout 5 miles from brooklyn and Michigan Speedway... for the summer anyway and i'll move back to Marshall closer to work... i'm from Monroe... make it to a get together this fall and we could swap details... why are you NOT sure whether you have a 350 or not? and i'm getting 4500 firm at 59 mph with a straight 21P mirage (not a Plus). i really have to trim it out til it is a handful to control to get that speed out of it too... i turn bout 4350 - 4400 with the trim all the way in...

Sam
08-19-2001, 06:23 PM
Let me clear things up, I do have a 350 ! What I don't know is weather it is stock. At Idle it sure sounds like it has a cam in it. I have asked others this question and they say it sounds like it does but who knows.

Sam

Moody Blu'
08-20-2001, 10:16 AM
my rotating assmebly IS BALANCED and my rods are shot peened and polished.The lifters are ford mtorsport racing lifters. I could rev that motor out to 7000 grand if I had a different cam and not worry about blowing **** up.(I built the engine toned down so I can later do mods and not worry about tearing the low end apart.)the reason the chip is 7000 is because it came with the rev control(only one chip), and I DOUBT that will ever happen since my hand is always on the throttle
your right though I am Illegal!
my distributor is not marine :eek:
neither is the ignition, but the msd 6t is sealed just like the marine ignition.
my starter and alternator are marine though.
I am buying a marine distributor and carb over the winter. If I had to buy a marine dist and carb, my boat would not have been in the water.
I know it has a certain risk to it, but I live dangerously.(foolish as it sounds) I know. my passion and impatientness for boating made me do it :p