wasted cam?
 

Well guys, after rebuilding both my SBC's one is acting up with only a few outings on it. I was cruising along at about 3,800rpms came up to a no wake pulled back on the sticks and the port motor tapped out. Got it restarted no problem, but you give it a little throttle under load and it just dies again. Idle sounds a little odd too, rev it up in neutral and the sound clears up, but then back at idle it sounds almost like a muscled up Harley.... When I first went out yesterday, when she was cold I had a little popping through the carb and driveability issues, once warmed up it seemed ok. Anyways, I am thinking a wiped out a cam lobe or two, three....whatcha think? Broke them both in for 25min at 2k-2,5k then changed the oil right away.

Other motor runs out like a top and pulls to 5,400, with no second thoughts. If the cam is wiped I think I am going to upgrade both motors to the XM270H or XM290H as I think the cams I dropped in were not what the doctor ordered anyway. I am wondering if the 290h will be too much and I will lose all my low end.

Twin sbcs
K&N 14x3.5 filters
edelbrock 1410 carbs
edelbrock performer air gap manifolds
RHS aluminum 64cc heads, factory 4 eyebrow pistons
comp 1.5 full roller rockers
edelbrock hardended +.100 push rods
224/224 @.050 282/282 advertised 465/465 cams with 114LSA
I run rotella oil with edelbrock zinc additive, and 93 octane pump gas.

Thanks, for any input

Check for water in the float bowls

It could be any of several things causing your issues. Assuming its cam lobes right off the bat without checking the basics first is a stretch.

It could be as simple as water in the fuel.

pull valve covers and idle engine. a little messy, but any gone lobes will be easy to spot.

if the cam lobes have problems i would think you would hear some ticking coming from valve lash?

sometimes not. the base circle is still there, just the lobe wiped off. and if exhaust is gone, it'll open just enough to idle, but blow fire back into intake at any load.

If it was bad fuel I am pretty certain both motors would be having the same issue, as they share same fuel tank. I wish it was that easy though, so would the bank account!

As soon as my next days off come around, i am going to start pulling the top end apart, and see what is going on. Do you have any thoughts on the other cams I am looking at as replacements? Or maybe isky or howards cams of a similar profile. I heard isky does all grinds in house, so to me sounds like a better quality as who knows where comp has there production shelf came machined.

Thats what I thought too, but between the thru hulls and the fact that the rockers dont always chatter loudly due to a bad lobe or two, I think I just missed the early warning signs.

I would check carb and ignition before going too deep. Hope it's something simple, bad wire or something.

Second that. I would seriously doubt it is a camshaft problem. Make sure everything ignition wise is cool, plugs, wires, cap, rotor, timing. Then check out the carb. A lean condition, for what ever reason it might be, will give you popping through the carb.

start with basics,vacume guage look for leaks,check timing,check valve adjustments,sounds as they may be to tight.compression test all cycls.

x2, and check fuel pressure at the carb.

if you can remove the valve covers easily i would check there first,if you do decide to change the csms go with the 270h,i just installed one snd the owner loves it,i would not go any bigger than the 270 with stock exhaust.

Is this boat Alpha or Bravo? If Alpha, check the shift interrupt switch - sometimes if out of adjustment or hitting ground these can cause intermittent idle and running issues.

Was this a hydraulic flat tappet cam? Before you pull it down, pull the oil filter off and check it for metal. If you rounded off one or more lobes, it will surely show up here. Much easier than pulling the top end apart for no reason.

If the cam is wiped, consider going roller the next time. The GM dog-bone roller lifter arrangement is cheap and nearly bulletproof, and GM has some off-the-shelf factory roller cams out there that would work well in a marine engine and aren't that expensive.