Whats up with all that Zone 5?

First let me clarify the $9000 deal... This included EVERYTHING attached to the motor as well. Anyone priced a Fuel pump/sea pump drive for a carbed HP500 lately, or an oil cooler, PS cooler, all hoses, 1 bent sea pump pulley, coupler, etc.... also had the drive checked out... Probably more like $6000 between heads. So if I mislead anyone about the cost of this thing..TOO BAD, the cost of the motor is not what this is about..

As far as the Cam goes, The Boat ran great with it for 40 hrs, and I was very happy with it. Economical, very strong low end.. yes it died out on top, but that's not what I was after. I doubt it was the cause of my troubles.. But, for the sake of argument, what is it about this grind that makes it prone to reversion or Detonation that your so sure of. I'm a very objective type, and am willing to hear any and all rational explanations.

I totally agree with you on the risers.. I'm going to have them extended all the way to the transom "dry", and eliminate the Silent choice.. I never used it anyways..LOL!

If you are running stock riser with that cam it would be a problem. You should see that problem as first a milkshakey crankcase oil situation. The exhaust lift is odd on the cam in combo with the intake lift, but that should just make it act like a smaller cam than the .650 suggests. None of this should cause the seat to fall out of a good set of heads. I really think you need a good set of alum marine heads with the right seat pressure (180 is way high) and ferria type valves and good springs. The aluminum will also give you a little additional margin if your comp is on the high side.

I know your pain all to well. I dropped a seat and took out a piston same heads as you. The exhaust valve was tuliped. I blame mine on detonation, suspect fuel, running with the Tabs stuffed and boat load of people. My perfect storm.

i just love reading this stuff,but the good thing is im going to the miami boat show thursday

Low end is the key here. I don't think you will ever find anyone that says they want or built an HP500 for low end. That wasn't its goal in life. 088 heads are not good at low end. They were made for the high RPM stuff, in the 4500+++ range. I can assume thats what you wanted, but the parts you had don't lend themselves to that. So mismatching parts didn't help you here. If low end was your goal, the person that picked your cam should have gone a totally different way than he did. I would have told you pretty much what I just did, that you had a motor designed to be high struing, and making it run down low was going to not work well.

The super high spring pressures on your valve train all contribute to issues with those heads. You usually run those kind of pressures with solid lifters and/or when you are spinning high RPM, which you weren't doing. No 540 HP motors go there. high spring pressures smack that valve closed, and depending on the cam ramp rates smack it even harder. Thats not good on the heads/lifters for long life. My 509 which made 625 ish power ran rates of 145 on the seat, and its still running 7 years later and never been apart. You know, based on what you just said, that your exhaust was an issue with reversion.

Per one of your posts, the staggered jets on the stock HP500 are great. but you can get around it without them. Merc spent a ton of time figuring them out, but most of us don't have their R&D money. Plus you also said that you did plug readings, and they were fine. Once you change anything on the intake, and/or exhaust as you did with that cam, Merc's stock setting go out the window.

37* total! i would say that was the killer rite their..same thing happened to me a years ago,was at 36* total and ran 93 at the time,had a friend put fuel in the boat and off we went..2 hours on the water and bang no more power..all my plugs were loose and one had the tip burned off..i asked my friend for the gas recipt and bingo 87 octane..i wanted to brake his nose and i told him 93...anyways i advanced the cam 2* and backed down the timing to 34* total..ran way better in the big end and i even picked up 200 rpm.s..

Yep, that looks familiar...

to clarify your reversion question, your motor has most likely been ingesting small amounts of water every time you idled it or flushed it. Every time this happens, the seat gets pitted by the cold water on the hot metal. Seats are very tough, but not indestrutable. over time (40 hours in your case), the seat is finally so pitted that it fails. once that happens and it gets into the cylinder in pieces, all bets are off. The heat from it can cause intense detonation, that heat can do lots of things, as is shown by the possible head gasket failure. The oil that is burnt on your piston is again from pure overheat baking the oil there. again as your seat has been pitting, the cylinder is not sealing anymore, so when all that super hot exhaust gas should be going out the exhaust, it also has a small path to the intake, meaning that when you get your next intake charge its not as cool as it should be. All of these on each cycle are very small, but over time they add up to big issues. As the # 7 cylinder is the 1st one to usually have issues on a BB, thats just one more thing against you. As far as overlap, I can tell you what it is on a 500HP cam, as thats just a crane cam. However, unless a different supplier was used, your cam is from bullet. Keep in mind that Crane and Bullett use a difference reference point in measuring their cams. So sets of numbers from the two of them side by side do not mean the same thing.

Water reverting into the cylinders will also cause your compression to go sky high. Water takes up space in the chamber. I learned this the hard way too........