Hot Exhaust Hoses on Ford 351w Inboard

kirch254

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Okay guys, I need some help on this topic. I have reviewed these forums for problems like mine and have used the answers to trouble shoot but still having problems.

Setup:
1992 Bayliner 3288 motoryacht
Twin Ford 351w with closed cooling system.

Problem:
Starboard engine 4" exhaust hoses (directly off the risers) getting hot. The port side of the starboard motor gets to about 250 degrees in the hottest spot but the entire hoses runs between 125-250 depending on the location. The starboard bank of the starboard motor runs between 90-150 degrees. In the picture you can see the black areas on the starboard hose and that's where the hose is getting hot. The picture of the hose that is completely black in the middle and gray on the ends is the side that gets the hottest. I have since replaced that hose and problem remains. The port exhaust hoses run about 85 degrees consistently on both banks.

There is not an external trans cooler on this setup. The transmission fluid runs through the heat exchanger like the coolant does. Some forums mentioned checking the fresh water lines that run to the trans cooler.

After reading the forums I have done the following:

1. Checked and replaced the impeller to make sure there was not an issue there.

2. Flushed and back flushed the heat exchanger. I was able to remove several pieces of impeller out of the raw water intake side of the heat exchanger. When I connect a hose to the raw water intake with the raw water exit hose disconnected the water seems to flow without restriction. So I am assuming the issues is not a blockage in the heat exchanger.

3. Removed the exhaust hose that was getting the hottest and ran water through the raw water system using a garden hose. I held a bucket underneath the rise to determine how much water was flowing out of the riser. The water appears to be running freely out of the riser. No obstruction visible and water seemed to be flowing out of all three "ports" evenly.

4. I put everything back together and ran fresh water through the raw water system again using a garden hose connected to the freshwater intake of the heat exchanger and can hear water flowing through the riser and out both exhaust hoses.

5. Started both engines and they run great but the hoses again got hot on the starboard engine.

6. Removed the 90 degree elbow from the hot hose again and looked up in the hose. The inside of the hose was mostly dry except for the top of the hose and way down the hose to almost where it connects to the 90. It seem I am getting water but it's either no enough to flow through the entire hose or the water is not being distributed to the right places.


What would you guys suggest I check next? Could I still have a partial obstruction in the heat exchanger or in the risers that is keeping water volume below what is required for proper cooling? I read on a forum that back pressure in the exhaust could cause an issue. How do I check for back pressure?

The forum would not allow me to post pictures.
 

alldodge

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Howdy

There isn't a lot of items for a closed system. Stated the impeller was changed, but if the housing is scored or worn it may not be pumping enough water.

Check your seawater pick up through hull, valve and strainer. Might need to go under the boat to get a visual of the pick up. See if you can find a brass tube brush to run thru the tubes of the HE. After that, its all hoses and fittings. If you riser is clogged up some it will restrict the flow.

Don't see exhaust back pressure being an issue, that would cause performance issues more then more heat.

Ford 888 closed cooling 302 _ 351.jpg
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Im going with lack of water flow thru the riser elbows. since these are raw water cooled, my guess rust and scale
 

Bondo

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Ayuh,.... Welcome Aboard,..... Is the boat in the water, or on the hard,..??

When you were checkin' the heat exchanger, did ya back-flush it with yer garden hose,..??
 

kirch254

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May 1, 2017
Messages
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Thank you for the responses..

I will check the water flow through the pickup, valve and strainer.

Bondo- Yes I used a garden hose to flush the exchanger and the boat is in the water.

I think my next step is to hook my garden hose up at different points of the system and see how long it takes to fill a 5 gallon bucket from the riser. I can do the same on the port engine that is not experiencing the issue and hopefully determine where the obstruction is in the system. I'm still thinking heat exchanger or risers.
 

kirch254

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May 1, 2017
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3
Update- I tested the flow on both heat exchangers using a garden hose on the sea water intake side and another hose connected to the raw water exit. On the motor without the heating issue it took 1 minute and 12 seconds to fill a 5 gallon bucket.. from the "bad" motor it took 1 minute 37 seconds to fill a 5 gallon bucket so I must have something restricting water flow in the exchanger. I have ordered a new heat exchanger to replace it.
 

Bondo

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Ayuh,..... That's not a Huge difference, But I guess it could be enough,.....
 
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