I'm having some issues with my BD4500 that no one can seam to figure out. The motor has Roller Rockers, Duals, and the big push rods. When it was new it would run 31mph and would get on the rev limiter long before WOT. The motor has about 41 hrs on it now and ever since it was new it seamed to me to be a bit noisy at idle. Basically like valve clatter. Of course I checked valve lash and everything checked out. I just basically wrote it off as just simply being a little noisier than average motor. For the first 40 hrs everything was fine. I did loose a little speed but figured that was just from prop wear. At 40 hrs I decided to add a set of high rev coils. Once they were installed I noticed that at somewhere around 4500rpm the valves would float. I never actually put it in the water at this point for fear of damaging something. I took it over to Andy's for him to take a look at it. He of course checked the valve lash, did a compression test and a leak down test. Everything checked out just fine but he did agree that the valves were floating at around 4500 rpm. He gave me a stock set of rocker arms to try and eliminate some of the clatter that I was hearing at idle and told me to go and run it to see how it acted in the water. Believe it or not, after replacing the rocker arms, the valves did not float. I sent the rocker arms to MB for them to take a look at it. Meanwhile I ran the motor and noticed that it wouldn't turn more than about 4200 and would only run about 28 mph. I then purchased a new prop to help make a true comparison from what it did new and what it does now. Now it's turning 4050 rpm and runs 29 mph. At this point the only difference between new and now was roller rockers and high rev coils. I installed the stock coils to rule a coil issue out and saw no change at all. Today, I received a call from Micah at MB. He said he tested my roller rockers and everything is perfect with them. He seams to think that the floating valves are a result of a weak valve spring(springs are shimmed).
Has anyone experienced these issues? Also, how would one go about identifying a weak spring?

To eliminate some of the obvious explanations for the loss in power, I can tell you that the bottom of the boat is still straight, and I have not added any weight, nor adjusted the distribution of weight in the boat.

First off...roller rockers are junk.

Secondly, what kind of boat is this engine on? Does it have flotation?

Custom built boat with no flotation. It's 19'6"x52" all 1/8th.

Next question...wtf is a Black Death 4500?

Exactly what mods have been done aside from those mentioned above?

Sounds to me then that the boat is running fine!

Perhaps the 31mph you clocked was in either shallow water or with a tail current.

first of all roller rockers are not junk. i don't use briggs valve springs but i have some out in the shop some where. i will try to get u a spring pressure setting and post back. or maybe take-em knows the rating. u can find a local motorcycle shop and have them presssure test them. all u have to do is air up the cylinder pull the keepers and have them tested. u are right tho they should'nt float at 4500 rpms. i just hope that u are not mistaking a valve float for a rev limiter bump. check ur rpms out of water. bring ur rpms up slowly past 4000 rpms and increase them u should be able to tell a floating valve versus a limiter bump. on any giving day my boat will run different mph.

I'm sorry Rich...BPS rollers suck.

Is the ratio the same between the rollers and the stock rockers? more valve travel will flow more air and change when things start to float.

No, different ratio.

Al has them.

The clatter you hear at idle is after market RR's, they will make a little noise under the valve cover. No big deal at all.

What kind of gas are you running in the motor, if running low octane you'll here valve clatter at higher RPMS and even coming off idle hard you'll hear it

The test conditions were exactly the same. The speed doesn't concern me near as much as the loss in rpm. 4350 at around 3/4 throttle vs. 4050 WTFO is a big difference. As for the floating valves, it's definately not the rev limiter.

What is the compression? What were the leak down results?

Pop the valve covers off and roll the motor over by hand. Look closely at the rocker arm travel, measure it if possible. Are they all the same? Push rods straight? What is the lash on each rocker?

When is the last time you changed your oil? Notice anything shiny in it?

The last time you brought this problem up, your motor was running fine, you reset your valve lash, then you started having issues. You did say that you eliminated the valve chatter though, and with the rr's that never really goes away... I'm thinking you over tightened one or more of the rockers and damaged your cam in the process. You may not have taken a whole lobe, but enough to cause some issues... (a fucked up spring could possibly cause similar issues maybe?, if you think that's what it is, swap them out, they are cheap)

Other than that, I don't know what to tell you. It does help to give folks all the info though. You are not saying the same things you said in your other thread and this appears to be the same problem. Anything else you are leaving out?

Only other thing I can think of is one your coils is shorting out...

Boat Dr. Is very good wif these motors. Couldn't something be flattening out on the cam?

Where are you located

Port allen