454 overheats when over 3000 RPM's need tech advice1

[LetsRock]

The intention of those flappers is to keep sloshing water from entering the manifold (think of them as a one way valve). You may want to conciser replacing vs removing entirely.

For full disclosure it was my mechanic and not me that removed them. He did say that some new boats today don't use them and they weren't necessary. Is that not accurate? Should I be considering putting new ones in?

 

[PMC]

New (and functional ones) are very tight. you can push on it and it will snap back with some force. The exhaust pressure is enough to open it.

I replaced a pair on an engine that ran for 10 min (from dead cold) without water cooling. Engine never came anything close to overheating, but the flappers were limp and shot from the dry exhaust temps. IMO this is a must check for any boat that overheats, or has poor water cooling.

 

[src]

For full disclosure it was my mechanic and not me that removed them. He did say that some new boats today don't use them and they weren't necessary. Is that not accurate? Should I be considering putting new ones in?

If a new system doesn't require the flappers, it's because it was designed that way. Yours wasn't - I suggest putting them back.

 

[LetsRock]

If a new system doesn't require the flappers, it's because it was designed that way. Yours wasn't - I suggest putting them back.

Thank you

 

[PMC]

For full disclosure it was my mechanic and not me that removed them. He did say that some new boats today don't use them and they weren't necessary. Is that not accurate? Should I be considering putting new ones in?

I'm not a mechanic, and not in a position to argue against somebody more qualified. Personally, I would replace them...the parts are under $100 if you DIY

 

[rcknecht]

I had a colapsing intake hose on my port engine that caused it to over heat above 3000 RPM. The hose was routed tight and and only colapsed when the boat was underway. A new longer hose with less bends solved the problem... Unfortunately, replaced water pumps and clean HEs and changed manifolds prior to finding the hose problem...

 

[Air O'Nautical]

I had a colapsing intake hose on my port engine that caused it to over heat above 3000 RPM. The hose was routed tight and and only colapsed when the boat was underway. A new longer hose with less bends solved the problem... Unfortunately, replaced water pumps and clean HEs and changed manifolds prior to finding the hose problem...

Yea, I hate when that happens...I have a customer right now with a overheating problem.
Has a new raw water impeller (hope it was installed correctly),heat exchanger is out for cleaning and testing, thermostat will be next....yada, yada...I hate throwing parts until it fixed..

Glad you back to normal.

 

[AFD]

Just a heads up. The scaling that collected blocking one of the return hoses to the manifolds was causing the problem I was having with the over heating. Probably a poor job winterizing by me. That won't happen again.

 

[CliffA]

glad you found the problem....as a side note to all others that may read this thread you should always use a piece of wire to wiggle around the drain plug holes when you winterize..... if you don't there is a chance scale and/or sediment has crusted over the top of the drain hole which prevents any water from draining out when the plug is removed.....obviously that causes a potential for engine damage from freezing water....just like you found when you inserted the wire into the drain hole there can be a substantial amount of water left in the engine from a blocked drain hole....wiggling the the wire in the drain hole will break up this crust so that the water can drain out of the hole....

cliff