I am from the Philippines and really need help on whats the best cam/manifold/carb combo to run. My boats engine is a Mercruiser/Chevy 350cubic 4 bolt main. I am currently running flat top pistons 0.30 over, 2.02in 1.60ex stainless valves, Milodon roller rockers 1.5, 31inch length runner tube headers (Custom made). MSD billet distributor, with MSD 6A ignition.
My boat is a 21 foot locally made fiberglass hull with 18 degrees of deadrise, a step, and notched transom. I run a Mercruiser 228 outdrive, with a 19inch straight-back Mercury stainless prop, and Bennet Sport Tabs.
Top speed is currently 54 mph on GPS at 4300rpm. I would love to get a bit more speed. Consumption at 35mph 2800rpm cruise is roughly 35liters/hour. All this was run with the crower cam, performer intake and 650 holley, but I don't know if thats the right combination.
I have two cams, manifolds, and some carbs in the shop and would appreciate any set-up help from more experienced guys here.
I have a Crane Cams HMV-260-2 with duration intake 204 and exhaust 216 at .050 and lift of Intake .427 Exhaust .454.
My other cam is a Crower 288H cam, with duration of 214 intake 224 exhaust at .050, and lift of intake 444 and exhaust 467.
My intake manifold choices are an Edelbrock Performer, and an Edelbrock Torker II.
For carbs, I have a Holley 600cfm vacuum secondary, a Holley 650 cfm double pumper.
I really need all the help I can get. Thanks!
1st off...WELCOME...u sound like u got a handle on it just as it is...MPH is pretty good for a 21' boat with a out-drive...i personally wouldnt touch anything for the summer...just go out & have fun...remember the old saying: "if it ain't broke...don't F*** with it"...the only thing i might suggest is to try a different prop sz & pitch...leave the rest alone & run it...u will get alot of replies to ur thread...but these are my suggestions...just my .02 cents
fastrat
p.s. lets see some pics!
Thanks! My dad told me the same thing. The thing is I dont know what the max RPM should be, so I was thinking of trying to squeeze out a few hundred RPM's.
The prop thing is a good suggestion. I might try a round ear for more bow lift, as I run flat at 50mph up.
Here are some pics of my locally made boat.
http://www.pix8.net/pro/pic/16417i8xI1/943376.jpg
I would appreciate any help the gurus here would extend with the best cam/manifold/set-up for next season.
Thanks again from the Philippines.
thats a pretty good looking boat for being locally built...i'm glad to see ur Dad & I are on the same side! lolother than a prop chng...small things u might try are: mill the air horn off the carb if its not done already! (p/u a few extra cfm's) chng the jets front & back (go up about 3 sz front & 5 sz back)...chng the rear acellerater pump to a 50cc pump...these are small chngs that wont get u in trouble...the boat looks pretty heavy, so i don't know what the max RPM should be...i have no reference to a boat that looks like urs...try these chngs & see what happens!...as far as over the winter chngs...i would build a stroker (383) & do some head work...larger int valves (2.05) & some port work (match int manif & exh headers to the heads)...higher comp pistons (10-1)...run the Crower 288H cam & a set of Comp Cams steel roller rockers...the performer manif is good...chng the carb to a Holley 750cfm dbl pumper/mech sec or go to a Edelbrock 750cfm carb (good carb)...this is what i would do if it were mine...most of the people on the boards that run SBC's have them in 18-19' boats (no hatch cover) with jets & a few run 2x4 T/R's...thats my suggestions & a place to start for now without getting into 2 much trouble (prop & carb)...go give it a try & see what happens!
fastrat
Thanks so much Fastrat!
Whats your thought on the Torker II manifold?
All the help is appreciated!
Whats your thought on the Torker II manifold?
i have never ran a torker/torker II manif...i believe they are sgl plane manif's & the performer manif is a dual plane...u really want the over-all drive ability of the dual plane...the torker II would prob give u a little more on the top end...but not as good on the low end...i would stick with the performer if its a dual plane!...go chng the prop & re-jet the carb & run it!
fastrat
p.s. it looks like u run ur boat in the ocean?...salt water?
Yes, the Torker II is a single plane, and the Performer is dual plane.
I run in the ocean all the time, and yes salt water. I usually flush my boat in a river near the house for about 15 minutes on fast idle after.
We get about 84 deg F air temperature here all year round, and the boating season is only limited by storms or big waves.
Hey fastrat, sorry I havent had time to check the forum out as my Dad got sick and stuff. But after 2 andioplastis, all is well!!!
Took the boat out twice, running the Performer intake, 650 Holley, Crower cam (00904), and I still hit 54mph. I am running 34 degrees advance at 3,000rpm.
The great thing is that I was getting 8.5gallons/hour running at 35mph (2800rpm).
Like you said, "if it works, dont touch it!!!"
However, do you recommend better ignition timing specs? I was also thinking of getting new valve springs (edelbrock 5794), new pushrods, and new lifters, just to re-new the rather old set-up I have. Is this okay?
Hey Paul...
welcome back...wondered where u went...i sent u a PM & never got a reply...anyways...how many people are in the boat when u reach 54mph?...does the motor feel like it still wants to pull?...i think u need to try another prop to get some more top end...the boat/motor combo u have is a good sea worthy combo & may very well be maxed out with what u have, no matter what chngs u make...i still think a prop chng will help...get one & try it...save ur money on the other parts for now...springs, lifters etc last along time unless u abuse them...let me know
fastrat
Sorry about that, just didnt have time to go online.
With 4 people on board, I can get to 54mph, thats at 4300rpm only. With 8 people, I can get to 51mph.
I am using a Quicksilver 19P straight back propeller. The problem I think is the lack or bowrise at top-end. I have the tabs up all way, plus my drive trimmed out, but couldnt get the thing to porpoise. I just feel there is too much hull in the water at top speed.
I have been told I should try a round-ear prop as they give more bowrise. What do you think?
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