What RPM's are constant?

[hdsadey]

Here's my dilemma, been around boating from a young age, all of it contained outboards! This is my first I/O, that being said I've been building engines for 20 years now but only for cars, which don't see sustained high RPM's like a boat. I have a 1999 Chevy Vortec 350 4 bolt main motor that I'm putting together for my 16. It's a roller cam motor. Now I understand the difference in the simple things like difference in gaskets. My concern is with the valve train. Here's what I have, stock Vortec heads with single factory valve springs, rocker arms, pressed in studs, factory push rods. Is this gonna hold up to sustained Rpm's at say 4500? Should I invest in performance valve springs, screw in studs, better pushrods? I know one thing can lead to another just wanna know where is safe to stop, small hatch doesn't lend itself to work on the engine so would like only to do it once!

[gcarter]

There're other folks here that know a lot more than me, but generally if a marine cam is used, the cam manufacturer will reccomend lifters, and springs. Other components can also be upgraded if you want.
I think any more than 3500 RPM for a sustained period of time is too much.

[VetteLT193]

As somewhat of an extension of what George is saying it will at least partially be how you are going to run the boat.

Some guys seem to ream the crap out of their boats. I'm a 3000 - 3500 RPM kind of a guy. Sure, I'll let it all hang out for a short period but for any given distance you can bet I'll be running around 3200 RPM.

If you really like to run fast a lot better stuff is going to be worth the investment.

Also... different people have different definitions of what reliable is. To me, 800+ hours is reliable. to others it might be 100 hours. there is a big difference there.

[hdsadey]

I know this is hard to answer but generally speaking with the right prop at lets say 3000 rpm what speed are we looking at for a 99' 16 with a 350?

[mrfixxall]

like stated,if your not planning on keeping the engine @ a consistent 5500 rpms for a long period of time then change to a better valve train components..comp cams makes all the up graded valve train parts you need,,if it were me but that's just me and i run my chit hard i would up grade..Keep in mind those heads need a certain rocker arm so the rocker arm stays in place so using a older style rocker arm wont work,their called self aligning which needs the tip of the valve stem to keep them from coming off the valve..http://www.sallee-chevrolet.com/images/p177897_image_small.jpg

[glashole]

I know this is hard to answer but generally speaking with the right prop at lets say 3000 rpm what speed are we looking at for a 99' 16 with a 350?

40mph

[Just Say N20]

I would hedge just a little and say 35 - 40 mph.

That depends a lot on the engine. If I remember correctly, Parnell's 16 is running 50 @ 3,000, but that is 500+ hp and an Alpha SS lower unit.

My 16 with a Volvo 290 (not as hydro-dynamically efficient as a Mercruiser Alpha), with one of the old school Volvo aluminum props, ran 30 @ 3,000 with around 290 hp. I'm told with the correct prop, I will be around 38 mph @ 3,000 and 62 mph @ 5,200. At least that is what the previous owner reported.

[osur866]

My cruise is 3650 rpm's @ 52-54 mph , all be it an 18 but that's the sweet spot for cruise for my set-up.

[MOP]

I went through this with the guy that setup my Darts heads, he asked me max RPM ans cam lift I said 5K & 510 lift full roller setup he said that I did not need the larger studs. It was in now way an expense issue was pretty cheap for him to pull a set of large stud heads off the shelf, I have about 260 hours on it so far. My cruise 3200 43mph do not do much above except the occasional short blast.