bcarpman

Longer duration, but a lot lower lift than my present cam, and way more overlap. My numbers were with wet, shorty marine exhaust, but no power steering, so I would guess this cam is only making about 20-30hp more.

Sounds like I'm not going to get as much from a mild cam upgrade as DD had predicted. Probably best to hold off. The engine runs great right now, and nothing leaks. Be my luck, I'd change cams and end up spinning a lifter next June. I want to keep my eye out for a HP525 manifold and Procharger for NEXT winter anyway

Raylar

bcarpman:

Only thing I see that seems a little off is the 114LSA on this cam. I know we are always worried about reversion, but carburated N/A engine tend to like a 110-112 LSA to make bigger power up in the higher rpms. The duration numbers and lift numbers seem good , but the 114 LSA cam is more like what a fuel injected engine would want for idle quality.
Did you degree in the cam and if so at what numbers?
If you dumping your water at the tips you should not see a real reversion problem unless there's little or no drop to the tips from the manifold elbows.
On your buildup and combinations listed here I should think you will be seeing about 550-570HP if everything is working correctly, but getting your peak power closer to 5400 rpms should give you some more prop speed and hull speed.
Good Luck,

Best Regards,
Ray @ Raylar

bcarpman

The cam is installed straight up.

I am confused by the comment regarding EFI engines wanting less overlap. I've always found EFI to be easier to tune for good idle at a given overlap, not worse. I know you know your stuff, so I'm just curious as to where that comes from.

thanks

Raylar

Wider LSA is less overlap not more. FI cams usually need wider LSA's or less overlap to keep the manifold vacume higher to better control the MAP signal especially at idle. You might be able to retard the cam about 2-4 degrees and improve the topend power peak , but be careful of the reversion issues!

Best Regards,
Ray @ Raylar

bcarpman

Yep, that's what I was saying, less overlap (larger LSA) for EFI wasn't making sense to me.

I get your point about the MAP signal though. EFI systems I've been working with lately have Hybrid MAP/TPS cal tables for radical cams. Makes tunning at idle doable with big cams.

SB

More cam duration will make it pull more rpm and create more power.

If the exhaust you describe above are Eickerts, definatley call RMBuilder as he has done many 502's and larger with these exhausts. Done a bunch with other exhausts too, of course.

Just imagine a short SS tube of this end of this:

KAAMA

I do not run a 525EFI cam, but I have heard a few 525 cams running in other guy's boats and I must say, they have some pretty good lope sound going on. I like the sound of the 525, but I was surprised at how choppy they sound----I guess in designing the 525, Merc was trying to get a lot of that power out of the cam profile in a 502cid engine.

I should say that I did just the opposite with my NA 565cid engines---my goal was to get more of the power out of the cubic inches, high flowing heads and exhaust system vs trying to get it from the cam. Heck, my engines run a smaller cam than the Merc 525!!! I can get away with a smaller cam because of the flow quality in the design of my heads. A smooth idle was my first priority---not HP, so I did this at the sacrifice of some top end power. My 565cid engines almost sound like the family van aka "grocery getter" compared to the 525/502cid. My 32' AT runs in the mid 90's GPS with full fuel and flat water.

ROTAX454

Do yourself a big favor, get ahold of RMbuilder. If you really want a cam for your specific build, he is the man. And yes, he has done this one with the KE exhaust.

KAAMA

HERE!!! I totally agree---RMBuilder/Bob Madara of Marine Kinetics is the cam with the cam! 585-654-8583 in N.Y.