Mike Paula

What is wrong here??
Back ground
1990 Checkmate 251 502/ Bravo 1
Motor is a GEN6 with edlebrock marine heads running a 502/502 cam. SSmarine exhaust and Gill muffler tips. Cam has to go.even with the 12" extensions I am reverting water at idle. I am thinking this cam CP has on there site duration I/E 224/ 224 lift .566 .566 lobe separation 112

Props I have run:
Bad 23 Mirage netting 5000-5200rpms (depending on trim setting) with a GPS speed of only 53
23Mirage Pluss 5000-5100rpms (depending on trim setting) with a best GPS speed of only 59.8
Last a 4blade 23 hydromotive 4900-5000rpms (depending on trim setting) with a GPS speed of only 58.8.


Tabs where dragging, but no more


Bottom looks straight, little hook in the pad area (look buy the word FAT)



Note the bottom paint, been slowly removing it. this stuff sucked ,run you hand over it and it would stick to it. still a lot mid ship.



look how wet this boat runs

I would think this boat should be in the upper 60?s lower 70?s with this motor. I have no ill handling as is. Ideas?
link to thread I had in props http://www.offshoreonly.com/forums/s...d.php?t=138669

BY U BOY

I Too Am Running A 502/502 Cam And Was Told It Is
244* ,234* @ .50"
.527" , 544" 110lsa That Is With 1.7 Rockers

I Just Got My Boat Running And Getting Wet Friday I Sure Hope I Do Not Have Reversion.

How Bad Is It In Yours

I Have A 454 10.71 : 1 With Marine Power Manifolds And Risers

Mike Paula

Not deluding the oil or killing cylinders. But after a long no wake zone it’s idling poorly. If I get it up to 1500 rpms there is no evidence when I shut it down and pull the risers. Its the 110 lobe separation killing it. I have extended my risers inner tube till it’s almost at the transom, help a very little.

Mike Paula

116 looks and no ideas? I am at a loss here. Is it the bottom paint, small hook, drive to deep, not deep enough, wrong props Help! What slowing me down?

Griff

Probably a combination of them all.

Rough bottom is probably costing you 3 mph and the hook another 2. How much hook is that and how far up from the transom????

You won't be able to prop it completely right till they are fixed. You can prop it to somewht mask the problem though.

SB

iTrader: (1)

I'd start with the bottom paint.

A few people here running the ZZ502 engine with no reversion problems that they are aware of. May depend on exhaust systems I guess.

ZZ502 is 224°, 234 ° at .050", ground with a 110°LSA. However, there is no published seat ° #'s or valve event #'s so who knows what the overlap and such really is. Anybody use a degree wheel on one of these ? Doubt it...doh !

BY U BOY

I Don't Think Your Reversion Problem Is With The Cam. I Did A Shake Down Today In My Boat With A Zz502/502 Cam With A 1 Hour Idle And Have No Reversion At All. What Angle Are The Exhaust At?

I Would Agree With The Above Comment About The Bottom Paint And The Hook.

brian41

iTrader: (1)

I had a 1989 25 convincer with stock 330hp 454 it ran 64mph add a stock 502 415hp and ran 71mph.I got rid of the hook and it got squirly got spun around by a small wave and almost killed me brused my heart and colapsed my lung. I bought my 32 Baja 2 weeks later.

Mike Paula

The hook is almost nothing. with the level against it you can barely see it. I heard it was added by checkmate. I have been thinking of sharpening the strakes and the transom edge. seeing if this will free it up along with finish cleaning off the bottom paint. Brian I have heard some horror story like your about removing the hook With mine as is, there is no ill handling at all. Had a little bow steer with the hydromotive prop.

As for my reversion. I have been thinking it is the tips. the Gil muffler tips seem to hold a lot of water. I have run this cam on Gil offshore exhaust and lightnings with no reversion at all. I have talked to stainless marine about it than they say it will this cam will revert.

Mike Paula

What RPM/pitch prop you pull?