Wellcraft Excalibur Stbd 502 Warms Up Dies amp Barely Cranks

"I have been looking at this i

"I have been looking at this issue for a while now. I need some help. The engine warms up fine at idle and if put under load or revving at dock in neutral over 2000rpm the engine will make an erratic knock noise for a few seconds then running smooth and quit for a few more seconds, then dies and is slow to crank like low battery. I checked manual oil pressure and showing good at 30-35psi the whole time. I replaced the oil pressure alarm switch at the rear of the engine and still happening. Any suggestions from here?"

Any water (milky sludge&#4

Any water (milky sludge) in your oil?

known strong battery? Good ground and battery cable connections at battery/starter/block?

Need to know more here. Start with the basics though.

"revving at dock in neutra

"revving at dock in neutral over 2000rpm the engine will make an erratic knock noise for a few seconds" Keep it under 1500 RPM.

When it restarts is there a cloud of blue smoke from the exhaust? What do the plugs look like? What year and how many hours on the engine? Does it require oil added between oil changes? What weight/brand oil are you using?

"The battery cables and electr

"The battery cables and electrical block at the starter are all brand new as I replaced them 1 month ago. The is no milky sludge in the oil as the oil was changed 6 months ago and I check it every time I start it. No water in the oil, thank god. The engine barely cranks after it dies like a weak battery but the batteries are all brand new also along with alternators, waterpumps, hoses, belts, the battery charger was just rebuilt also. The plugs only have about 100 hours on them. The oil is Synthetic 20w50 valvoline with Mercruiser oil filters. I am at a loss and any advise would be great to have. I am kind of worried about the brief clatter noise from the engine intermittently, but with a constant 30-35psi oil pressure even when the engine shut down, its hard to believe its a mechanical problem. Hopefully this will help make everything a little less vague."

"have you checked ignition tim

"have you checked ignition timing, if its to far advanced you will get a pinking sound when you rev the engine and it will also make it hard to turn over because it will be trying to fire to soon."

"this is going to sound basis,

"this is going to sound basis, but check all your battery and cable connections again. they need to be very tight. If you are getting resistence between a connection, you'll have your crank problem.

Not sure about the noise though. May be cross fire due to moisture under the distributor cap or something."

"Joshua:

Ged and "Profe

"Joshua:

Ged and "Professor" Hays have good points to follow. I installed a new (3) batteries last April and could not think of what was wrong when it hesitated to crank. Thought it was a new "dead" battery. Turned out to be a cracked ground cable connector; found it when I removed the cables to get another battery.

Did you change the battery ground cable to the engine block? Clean and retighten it. In fact, I clean new battery terminals and cables due to tarnish build up before installation; what about you? I also use RED battery terminal spay for corrosion protection."

"Thanks everyone. I am going d

"Thanks everyone. I am going down to the boat on Sunday to check everything out. I will check the battery cable connecters again to make sure. I will also check ignition base timing also. Question though, do I have to disconnect a wire for the computer to not trigger advance like on older computerized ignition systems with distributers similar to mid-late 80's GM V8 automobiles or just hit it with the light. Also, I am going to run a compression check on all 8 cylinders another individual said the 502s were known for piston slap. I will also pop the cap and check for moisture. Hopefully something will come up minor as the engines should be good with only 498 hours original on them. Thanks again guys. If you have any other advise or things I should check, let me know. Also, if you know of any good mechanics for the boat in the San Pedro, CA area then get me in contact with them too."

"Joshua,
I own a marine servi

"Joshua,
I own a marine service business in Newport Beach that specilizes in marine EFI engine diagnostics, repair and evaluation. Maybe I could take a look at it. Let me know.
Dave"