Rubber exhaust tube problem

[ricksi]

I recently replaced my MCM 260 engine with a new Vortec 5.7. Shortly after replacing it, I developed a leak in the straight 3" hose that connects the exhaust riser to the cast elbow. The connectors were old so I replaced them all on both sides of the engine with OEM parts (including the 3"-4" ones). I took the boat out and for a while it was fine, but when I opened it up for a period of time, the new 3" straight connector on the other side, ruptured. The rupture occured close to where the clamp is but it looked like a chunk melted away. When I replaced the engine, I switched to freshwater cooling and am using a 180 degree thermostat. Could the additional heat imposed by the freshwater cooling and thermostat change be the problem? Or is it possible that I purchased a defective rubber connector?

 

[Seven8385]

Re: Rubber exhaust tube problem

Sounds way to hot, my old 454 only ran to 150 and my 4.3 l stay at around 130 to 140.

 

[ricksi]

Re: Rubber exhaust tube problem

Does the change in water temperature have that big an effect on the exhaust temperature?

 

[Don S]

Re: Rubber exhaust tube problem

Pull the hoses back off and see if they are all charred and burned up inside. Bet they are. That is due to lack of water.

Post a picture so we can see how you have it plumbed for the FWC system,

 

[ricksi]

Re: Rubber exhaust tube problem

I just pulled off the 2 on the other side and 3 of the 4 still look like new. It's a Seakamp FWC and I double checked the hoses from the heat exchanger to the risers and they're configured exactly per Seakamps instructions (top right side of the exhanger).

 

[Bondo]

Re: Rubber exhaust tube problem

I just pulled off the 2 on the other side and 3 of the 4 still look like new. It's a Seakamp FWC and I double checked the hoses from the heat exchanger to the risers and they're configured exactly per Seakamps instructions (top right side of the exhanger).

Ayuh,... Has the raw water pump impeller been replaced lately,..??

 

[Bt Doctur]

Re: Rubber exhaust tube problem

you dont list the drive but sometimes the impeller does not move enough water thru
the heat exchanger, a larger belt driven pump is used.

 

[ricksi]

Re: Rubber exhaust tube problem

It's an Alpha one drive. I recently replaced the impeller.

 

[ricksi]

Re: Rubber exhaust tube problem

I guess lowering the thermostat temperature will not help if it's an issue with too little water flowing through. Is 180 too high, should I lower it regardless? I suppose for the flow issue I'll have to consider a seperate pump. I did a search and found the Johnson crank mounted pump. Would this be a good choice?

 

[Philster]

Re: Rubber exhaust tube problem

180 is not too high for the exhaust (as for the engine, I don't know if it is best at that temp or higher). It's not the issue. The hoses are getting way hotter than that because the exhaust is overheating. The exhaust is still cooled from outside water (raw), not internal (fresh water). Look, with a 160 t-stat she'd probably run 170-180 anyway.

I believe a 250-degree rating on an exhaust hose would be the lower end. Most are capable of 300 degrees or better.

 

[ricksi]

Re: Rubber exhaust tube problem

I just spoke with someone at SeaKamp, the maker of the cooling system. I was told that the exchanger has little effect on the flow rate from the outdrive. He also recommended that I test the flow, which should be 12-14 GPM, by disconnecting the supply hose and measuring the time it takes to fill a 5 gallon bucket (should be approx. 20 seconds). Finally, he recommended that I change to a 160 degree thermostat because the 20 degree increase has a negative effect on the viscosity of the oil.

 

[Bondo]

Re: Rubber exhaust tube problem

I just spoke with someone at SeaKamp, the maker of the cooling system. I was told that the exchanger has little effect on the flow rate from the outdrive. He also recommended that I test the flow, which should be 12-14 GPM, by disconnecting the supply hose and measuring the time it takes to fill a 5 gallon bucket (should be approx. 20 seconds). Finally, he recommended that I change to a 160 degree thermostat because the 20 degree increase has a negative effect on the viscosity of the oil.

Ayuh,.... Sounds like Good advice to me,....

180? ain't to high for a closed cooling system, 'n efficiencies should be realized if the motor is tuned to it...

You need to find out Why the impeller ain't movin' water, or if it is, where's it goin'...??
As it obviously ain't makin' it to where it's supposed to be...

If ya get the recomended flow in yer Test, try it After the exchanger...
Is the outflow goin' to the manifolds, or just the risers,..??
Have the risers been inspected,..??
Have they ever run in Saltwater,..??

 

[Philster]

Re: Rubber exhaust tube problem

Changing to a 160 doesn't mean she'll run 160. She might, but she might run 175 or just as hot as she does now.

 

[ricksi]

Re: Rubber exhaust tube problem

Only runs in saltwater. The motor, manifolds and risers are all about 6 months old and I added the FWC (full system) before running the engine in the saltwater. I ordered another rubber tube and will try it again. The more I look at the other tubes, the more I think there may have been a defect in the one that failed. The others still look new.