More 500HP questions
 

Hi everyone,

Been lurking for a few months and love the wealth of information here. I recently purchased a 1998 Crownline 266LTD with a 500HP carb motor. Motor has 210 hours on it and is completely stock but it has a miss in it from about 1500 rpm up to about 2800 rpm. At WOT and 5200 RPM i think i hear an occasional miss but cant be sure. Put new plugs in her, but no better. Next step is to install new wires and dist cap. Plugs were fouled pretty bad. It also starts hard after warming up and the exhaust smells rich. If wires and cap dont help i am thinking i need to rebuild the Holley.

Do you think i am heading in the right direction?

One more question....it has the stock Gil Marine exhaust and the original owner gave me a set of mufflers. My wife thinks the boat is too loud, so i am thinking about putting them on. Other than the slight horsepower and RPM reduction, can i do any harm to the engine by installing them? I had a local mechanic suggest that the mufflers could restrict the flow too much and cause damage. Would like to install captains choice, but if the mufflers are free why not try them first.

Thanks for the help!!

tim

Not sure about your miss, but definitely tell the wife the mechanics version of the mufflers!! Lol. Don't muffle the BBC man!! That's one of the biggest things I like about my boat.. and I get to crank 2 of them!

Welcome and good luck..

If the boat was sitting for a while, pull the heads and change the head gaskets, along with a new valve springs, and have the heads gone through, I had the exact same problem. HP500 motors need heads done apprx every 200 hrs, and they burn rich as hell at idle, change oil every 25 hrs. My head gaskets burnt through between cylinders, not pretty, new heads and block had to milled quite a bit. Extreme solution, but will save you thousands in engine work. But really as a start get a compression check and leak down check by a very reliable Hi-performance dealer / engine builder. As far as the mufflers are concerned, it depends on the manufacturer, some don't reduce performance, some do. Get what they call turn downs, don't reduce performance at all. .02

HAHA...i like that one. I love the sound too.....especially in a no wake zone under a low bridge. :D

Thanks for the feedback..the PO only put 3 hours on the motor over the last 2 years. Will get on the compression and leak down tests ASAP to try and get this figured out. Will let you know what i come up with.

thanks again.

I had the "power valves" in the carbs fail. Basicly small rubber diaghrams. Made the engines run extremely rich.

If your oil is clean I'd say its not the heads. Milky then yes. I'd bet the coil/ ignition is on its way out. Probably gonna leave you stranded soon.

I had a problem like that since I replaced the motor. I changed everything, carb, dist. wires. Turns out I was running the wrong plugs. I felt pretty dumb.

what plugs were you using and what are you using now?

I replaced the coil (it was leaking fluid) the distributor cap, rotor button and wires. Cap and button looked a little worn. Still running rich and has a miss at mid range. Rebuilding the carb now. I noticed that the right rear jet was a fan while the others were more of a stream. Should have it all back together and tested late this week.

Update.....

Pulled the carb off and it was in pretty bad shape. Power valves were failed and lots of build up inside of bowls, etc.. It looks like the PO definitely used fuel with ethanol. Everything is cleaned, new kit installed and will take her for a test run on Friday. Hope this was the problem.