Recurring Engine/Exhaust Hose Issue

[Tumbling Dice]

Hello a friend of ours who has a 1998 Carver Santego 380 is having a recurring problem. Please take a look at his email.

I currently have a pair of Horizon 8.1 L 370 BHP 496 cu. in. engines. My port engine has problem where at high rpm it burns a half inch hole in the exhaust hose, 4" down from the riser elbow. It burns the hole typically (this has happened 3 times) at 3000-3200 rpm. It doesn't do it consistently. I ran yesterday at 3200 rpm for a hour, throttled back to 1600 rpm for 20 minutes and then shut the engines off. I then started up again and ran at 2200 rpm for 30 minutes and discovered the problem upon entering the harbor at 600 rpm. Previously, I have run the boat at 1600-1800 rpm for 6 hrs straight without an issue. Any thoughts would be much appreciated.

I'll forward any questions and your advice on to him.

Thank you

 

[btoran]

fresh or raw water colled? do the risers get hot? when were the risers last checked or changed? i'm guessing it's either a water flow problem to the risers (ie raw water pump issue - maybe as simple as requiring a new impeller) or an issue with blockage in the cooling system (ie blocked heat exchangers / risers, or manifolds, if raw water cooled).

 

[cwms]

btoran is right. Your friend has a water flow problem. With proper amounts of water flowing thru the exhaust, you should never burn up an exhaust hose.
Find the reason for low water flow and you will solve the problem.

 

[Unknown]

One time as a kid our risers got so badly clogged that the mechanic used some sort of stuff to clean out boilers on them. If it was spilled on the concrete it ate it! But it solved the problem...

Not sure if its worth doing that today - its easier to replace the risers. Find out if they are clogged first though...

 

[DennisC]

Similar problem with 1990 Volvo Penta (Chevrolet V6) engine. No water comes out of one side. Actually, the heat exchanger was the next thing on the list to check. Risers just cleaned. Raw water (salt) flow from pump seems just fine. There is water in the exhaust manafold but it does not seem to flow out to the sea. I hope we are getting close to the solution!