Need some opinions on engine build
 

hey guys, i know most of you are running bigger boats with higher hp but i think you could maybe give som valuable input. I have a 1987 Concord Magnum II. Its 20 ft in length and weighs about 2500 lbs with a 260 hp merc 5.7L. it runs on GPS around 53-55 at 3000 ft above sea level with a 21p laser II. I am currently building another engine for it. It is a 97 vortec 350. I am using an edelbrock performer rpm intake, vortec heads, 9.72:1 forged flat top pistons, the original qjet, and switching to a roller cam and roller rockers. the rockers are 1.6 and the cam spec is 218 degrees at .500" on the intake side and 228 degrees at .500" on the exhaust side with 112 degrees lobe seperation. the cam actually gets .525 lift with the 1.6 rockers. was wondering what kind of power i can expect at 5000 rpm and maybe what kind of prop i should use to get max bow lift and top speed, also maybe an estimated speed.

I don't know if you're planning on running the stock exhaust, if so don't. There is/was a nice set of SB stainless marine exhaust system in the swap section.

what would be the issue with stock exhaust??

The stock stuff is junk from a performance standpoint.

You are talking about lots of time money and effort.
Is this the platform you want to invest in?

Uncle Dave

Give him good advice Uncle Dave, tell him to buy a faster boat.

Boy ...on one hand I mod everything so its hard to say that.

If you want to do it and you a a very capable guy well help you.

87 the size of your boat isnt the issue, its the viability of it as a performance platform - Oh you can get there...but its likely going to cost more than you think.

I would also say that you are likely to be frustrated with the end result and astonished by the price.

87Mag- alpha or Bravo? Whats you TOTAL budget?

If it were me - Id simply play with props and enjoy what is probably a really neat boat that runs well and doesn't give you any problems.

is this semi close to what you have?

http://www.concordboats.com/Magnum-II.html


Uncle Dave

Agree after working on my own little project I've spent about 2 k more than I thought and I'm still not quite done. http://www.offshoreonly.com/forums/d...3-eclipse.html

Nice project, its coming along. Ill do some more reading- nice documentation I know how time consuming it is.

Hey...does your girl have a sister?

Uncle Dave

thats the exact boat i have, differnet colors but you get the idea, and by the way i have less than a $1000 in the whole engine project, the block and heads were freebies, i know im not going to get 100 mph out of this thing but i was hoping for mid 60's. its a 20 ft boat, how fast do i really need to be going anyway? lol

its an alpha drive by the way, forgot that earlier

sunshadow,
been following your build, looks really good, i will post pics and progress once i get mine under way.

uncle dave,
the owner of concord is the one who pointed me in the direction im going, he has done it to a few of their boats and says its at least a 10 mph gain, im running mid 50's (yes thats gps) with old stock stuff now, cant see where it could hurt to do what im doing but i will keep you guys posted and if it flops i will gladly accept a few "we told you so's!!" anyway thanks for your input and i will keep in touch, im kinda new to the performance side of boating so im only dipping my toes for now, who knows what the future could bring!!

With only a grand in it you cant get too hurt.

Typically it takes 20 ponies for a solid 1mph increase so thats 200HP for 10 mph.

Not trying to rain in anyones parade, but more to help with expectations. Good luck and keep us informed on how it goes.

UD