Exhaust leak engine performance issues?

[LIGHTFOOT]

HI,
A freind of mine has a Liberator with a 460 Ford. He has had trouble bringing this boat up on plane since he bought it this spring. He has changed props a couple times and that helped, but not cured the problem. He found that if he left the engine cover off, it helped improve his engine performance alot. Does this sound like the result of an exhaust leak to guys? He says it has a slight leak. Your input is appreciated.


---------
Larry

 

[Euro95]

Re: Exhaust leak engine performance issues?

The exhaust leaks into the boat? So where is the water going, into the bilge?

 

[180shabah]

Re: Exhaust leak engine performance issues?

Boat engine compartments are closed but not sealed, if he has to open the hatch just to get the boat on plane he has issues.

He needs to stop "screwing" with props and start troubleshooting the problems.

 

[Mischief Managed]

Re: Exhaust leak engine performance issues?

He found that if he left the engine cover off, it helped improve his engine performance alot. Does this sound like the result of an exhaust leak to guys? He says it has a slight leak. Your input is appreciated.


---------
Larry

Sure sounds reasonable to me. He knows he has a leak and he knows fresh air helps a lot. Fixing the leak seems like a given regardless.

 

[mkast]

Re: Exhaust leak engine performance issues?

Sounds more like a problem with getting enough air to the engine for combustion.

 

[HT32BSX115]

Re: Exhaust leak engine performance issues?

I had exactly the same problem with my OMC 460. It would only turn about 4200 at WOT and had very poor power out of the hole.

I don't know why leaving the cover off would help. There's a LOT of room around the sides of the back seat that allows air in there....

I tried everything including rebuilding the carb, checking compression (all 160psi except 1 which was 155)

I tried all new plugs, and all other ignition components. I had 2 props. a 19 pitched to 20 and a 17.

My brother bought the boat new and it routinely ran 5000 at WOT and went 60 (GPS)mph using the 20p prop.

A minor exhaust leak will not reduce power. It will just cause a little noise or exhaust smell...


When I pulled the engine I discovered that the camshaft had several flat lobes.

A flat cam will absolutely kill RPM and power. I pulled the engine to rebuild it and would have done that if it was worth rebuilding. NO OMC 460/King Cobra is worth rebuilding. If you pull it out because it needs to be rebuilt, you should probably find another engine
to replace it with.

You could probably put a built up 351 in it's place if you wanted to stay OMC. A 429/460 would be a good engine if you could find manifolds or a coupler easily. I think there is someone making couplers now and you can occasionally find new old stock manifolds.

There's also adapters out there that would allow the use of 454 manifolds. (someone on here has done that) but you're still stuck with a drive that some parts are just not around anymore.

All my King Kobra stuff is still sitting on a pallet in the shop. I guess I should try to ebay it or something.....

I went in a different direction.


Cheers,


Rick