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Burton
09-02-2002, 06:09 PM
From all the experience out there, can you guys suggest what options I should consider on the most cost effective way to increase HP/MPH on my 1994 205 Merc with 95 Vortec Heads and a 19 pitch LaserII.Top end right now is almost 50 @ 4900rpm.
Does anyone run a 8cyl on their 16? Was it Original Equip or a swap. Can swaps be done easily? What the best small 8 to implant? Cost? Top End? HP? Love the 16's size, Do I have to go to an 18 footer to get the speed?
Thanks for your Help!! :cool: :cool: :cool:

Sam
09-02-2002, 06:22 PM
There are lots of 16's out there with V8's, mine included. Before you turn the first bolt you need to ask yourself "what is my budget". Most guy's get good results with changing over the top half of the motor IE cam, heads, intake, carb. I currently run in the low sixties and Jammie Root is now in the mid sixties with his 350 16.

Sam

MOP
09-02-2002, 06:49 PM
You can do quite a bit with what you have, I also echo the buget thoughts. A 4 barrel and a decent cam, through transom exhaust should make you pretty happy. I run a mild 302 that does not quite break 60, do your mods and you blow me away.

Bad-Tat
09-02-2002, 08:08 PM
Burton,
You should be getting more than 50 out of that set up. My 16 does 55.3 gps with the 4.3 4 barrel. I run a 21 prop with a Cobra drive.

Rootsy
09-03-2002, 12:13 PM
you should be running in the low to mid 50's with that combination... i was around 52 - 53ish out of the box with a 14 x 19 vengence, turning 4400 rpm with a 1.5 ratio drive.

i echo sam and phil on the buget thing... besides the buget you need to determine what will make you happy for top end speed. if 60 is your goal you'll need around 270 or so prop shaft hp (300 crankshaft), maybe a bit less with the V6 due to weight reduction. running a cleaver or a turbo prop (or somethign similar) will help keep it under control. i havn't tried a laser yet...

your easiest option to begin with would be aftermarket intake and carburetor if you dont have a 4V already, which i believe the 205 does already have. you could play with some ignition, followed by valvetrain too. if you dont want to go with a valvetrain you can also play with different rocker arm ratios. to replace a camshaft you'll have to remove the motor as well as cylinder heads most likely to do studs, springs, seats, guides and seals. and at that time it may be more feasible to just replace it with a 350... Not totally sure but the front motor mount locations would probably change and a sbc in a 16 is TIGHT TIGHT TIGHT to say the least. all of your accessories abd brackets would likely be the same though so you could swap from one to the other. You'd also have to invest in some exhaust.

sooo before you go shopping you have to consider how much you want and how much you are willing to spend for it... the 4.3L isnt cheap to do or as popular as a V8... you will still have to realize that the 16 will ride a lot looser and different than the 18... and more so the faster you go... minimizing chinewalk and improving handling is probably one of the best things ive tried to do thus far, second was adding a lot more ponies...

FastFranky
09-03-2002, 04:29 PM
Ive been told my 16 (all stock) with the same engine runs 55ish (my speedo dont work). My prop is a quicksilver 23 Pitch 3 blade stainless steel. 4900 is actually at the very end of the RPM range of that engine (I think 4800 is redline), I would try a prop with more pitch than 19. Just my .02

HyperDonzi
09-03-2002, 05:01 PM
when i asked this about a 4.3l, i was told to buy a 350. by the time you build up that 262 ci to what a moderatly built 350's power, you could have already bought the 350 and it will be more reliable.
i also remember, to get the most out of that carb, you need a new intake, then cam, heads, pistons................

Rootsy
09-03-2002, 07:07 PM
something is wrong somewhere with this combination of rpm, speed and engine package... is your speed reading from gps or speedo,etc? has the sterndrive been replaced on this boat, assuming it is mercruiser?

Burton
09-03-2002, 07:20 PM
Jamie, Its a merc, with a 19 pitch ss Laser II,
reading the speedo,..thats all that avail. to me!

mattyboy
09-03-2002, 07:34 PM
I have a v8 16 and there is something to be said for the 4.3 mild tuned it is lighter than a v8 and will run mid 50's all day, something is a miss with your setup,
how fast to you want to go = how much $$$$$$ you want to spend

Matt

Rootsy
09-03-2002, 07:44 PM
using your 19 pitch prop spinning 4900 rpm and the following drive ratios here are the speeds... adding 1 inch to the prop for cup

1.84 gear ratio, 10% slip: 45 mph

1.62 gear ratio, 10% slip: 51 mph

1.5 gear ratio, 10% slip: 56 mph

my motor @ 210 hp from the factory would spin a 19 pitch prop to 4500 rpm with a 1.47:1 gear ratio... 4.3L motors don't come in 1.5 gear ratio form as standard, i don't even kow if it is an option these days actually.

you want to prop the boat in such a manner as to have the motor operate in it's recommended rpm range which is given by mercruiser... which is found on the black flame retarder cover on the motor. going up 2 inches in pitch will drop you about 400 rpm. so going from a 19 -> 21 will take you down to 4500 or so rpm... your speed will likely stay relatively the same but it;ll bring the motor back to a more efficient rpm range.

Burton
09-03-2002, 07:44 PM
How high a pitch is too much? 23? 25?

Burton
09-03-2002, 07:47 PM
Can I tell from a serial number what drive ratio is on the outdrive?

HyperDonzi
09-03-2002, 08:45 PM
if it is an alpha, itis probably a 1.84 ( i think) and stay in the 19-21 pitch range.

TRU-JACK
09-03-2002, 09:25 PM
I have the 4.3 LX in a 16 with the 1.84 ratio and i can turn a 23 mirage (not plus) nearly 5200 rpms around 52 mph. Looking to try some 25p props this fall and hopefully find one that is just right. I guess you'll just have to narrow down the unknowns and get things dialed in. Good luck. wink

HyperDonzi
09-03-2002, 09:31 PM
tru jack, that isnt stock is it? with a 25p turning 5200 if it is, something has to be off.

TRU-JACK
09-03-2002, 10:10 PM
i'm turning the 23p nearly 5200 :confused:

Rootsy
09-04-2002, 08:07 AM
i believe the first thing i'd do is whip a GOOD tune-up on the motor.. assuming everything internally is in tip top order... this includes

distributor cap, rotor, spark plugs, fuel / water seperator and the fuel filter screen in the carburetor. thoroughly clean the flame arrester, verify that the ignition timing is correct (both initial and at full advance) and that you are truly getting full throttle at the carburetor.

if that doesn't help i'd consider a new coil and spark plug wires. Check for any exhaust restrictions also.

might as well have it running well before doing any motor work. that motor should be ringing the heck out of that prop. especially from som eof the comparisons with the other guys running 4.3's. there should be a sticker on the sterndrive tellin the ratio.. also stamped into the port side where the sterndrive bolts to the transom assy stamped into the mercruiser decal is the gear ratio... least on my alpha Gen II.