Re: 3.0 liter OMC exhaust riser hose
I have a 1988 Four Winns 160 Freedom with the 3.0 liter OMC engine. I have twice now replaced the exhaust hose connected to the manifold riser. It has blown out both times. Seems like it just gets hot and melted a hole in the hose. Any ideas on how to fix this? Thanks
Howdy,
Welcome Aboard!
Your exhaust hose is getting hot because there is insufficient cooling water flow through it from the engine.
All the cooling water from the raw water pump goes through the exhaust manifold and exits through the riser.
If there is a restriction anyplace in the circuit, water flow will be reduced. If it's reduced enough the exhaust system will run much hotter than it should (and the engine itself may not get hot)
Start by checking how much water flow you have from the pump to the thermostat housing.
Put the boat in the water, disconnect the hose from the transom mount to the t-stat and run the engine at idle briefly and see how much water comes out of the hose. It should be a pretty good stream and should increase if you rev the engine
If you have good flow, you could either have a restriction at the t-stat, exhaust manifold or riser. If you don't, you might have a restriction in the hose or piping in the transom mount or even a defective raw water pump.
A lot of the cooling water actually bypasses the engine (only a small amount is actually allowed into the engine, controlled by the thermostat as needed to control engine temp) Most of it goes directly to the manifold and riser and mixes with the exhaust.
If there isn't enough water making it out of the riser or manifold (because they're clogged with rust) the manifold riser and any components downstream will get hot. In some cases VERY hot!
Regards,
Rick