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Old 30-05-2012, 11:24   #1
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Engine Running Too Hot.

I have a Mitsubitshi 28 HP diesel generator motor that I have refitted to run my 33' sailboat. It runs so hot that it burns up my mufflers. The exhaust hose is 1 1/2" which is what the impeller people tell me is only good for 10 hp, but that is what my earlier motor had and it worked fine since 1990.

The impeller on my previous motor had a different number of vanes than the manual said to use. Could this help me problem now? What do you suggest I do? Help! I want to go sailing.
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Old 30-05-2012, 11:35   #2
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Re: Engine Running Too Hot.

So this is a Generator diesel motor that you put a transmission on and you are using it to power the boat? You have a wet exhaust system and it is getting too hot? Have I got this right? It sounds like you dont have enough water flow, the heat exchanger used for the gen set maybe isnt up to the task of powering the boat...? Maybe you could add an auxiliary heat exchanger? Just thinkin out loud..... does s good amount of water come out the exhaust?
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Old 30-05-2012, 18:06   #3
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Re: Engine Running Too Hot.

I would definitely go for an impeller with the right number of blades. Then the too small exhaust tube will overheat too if the engine is pressed. Maybe start with such things then go for the bigger issues like cleaning the exchanger, etc..

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Old 30-05-2012, 19:35   #4
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Quote:
Originally Posted by Calusa Sailor
I have a Mitsubitshi 28 HP diesel generator motor that I have refitted to run my 33' sailboat. It runs so hot that it burns up my mufflers. The exhaust hose is 1 1/2" which is what the impeller people tell me is only good for 10 hp, but that is what my earlier motor had and it worked fine since 1990.

The impeller on my previous motor had a different number of vanes than the manual said to use. Could this help me problem now? What do you suggest I do? Help! I want to go sailing.
Just to be clear. Does this conversion include a wet exhaust system or is it dry exhoust and you are asking if the closed cooling system impeller needs more flow?

What is the water temp running at? Are you getting any blowover on the pressure cap?

Need a better description of the system...
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Old 31-05-2012, 09:54   #5
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Re: Engine Running Too Hot.

Ex-Calif is right. We need more info.
How long is the hose between the water injection elbow and the muffler?
What is the capacity of the raw water pump?
Can you post a photo of the installation.
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Old 31-05-2012, 19:36   #6
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Re: Engine Running Too Hot.

This silly motor didn't come with a heat guage. But I haven't had any problem with leakage at the pressure cap.

The heat exchanger is the same size as the one on the old motor and it cooled well.

The motor is a Mitsubishi 28 hp diesel, 3 cylinder, fresh water cooling, with a 1 1/2" Exhaust hose.
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Old 01-06-2012, 11:38   #7
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Re: Engine Running Too Hot.

I thought the original motor was 10hp...? Guess I got that wrong. So the heat exchanger is off the old motor? What does "same size" mean? You can buy a digital thermometer for about 25-30 bucks. Test the engine etc and see what's going on. Maybe the engine is fine but you're not getting enough water to the exhaust pipe? DId you have to make a mixing elbow?
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Old 01-06-2012, 13:16   #8
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Re: Engine Running Too Hot.

Quote:
Originally Posted by Cheechako View Post
I thought the original motor was 10hp...? Guess I got that wrong. So the heat exchanger is off the old motor? What does "same size" mean? You can buy a digital thermometer for about 25-30 bucks. Test the engine etc and see what's going on. Maybe the engine is fine but you're not getting enough water to the exhaust pipe? DId you have to make a mixing elbow?
Sorry for the confusion. The original motor was a 28 hp like this one. Same size means it was physically the size in width, height and depth.

Unable to run engine long enough to get water hot without the muffler and enhaust hose installed.

I did not have to make a mixing elbow. It was designed with one.

Thank you for you concern.
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Old 01-06-2012, 13:43   #9
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Re: Engine Running Too Hot.

Is there much water going into the exhaust? regardless of engine temp, I would think the exhaust would be fine...if it's getting water flow......? Maybe a blockage in the water entering the exhaust elbow? You currently have no exhaust installed as the old one burned up.. right?
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Old 01-06-2012, 14:13   #10
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Re: Engine Running Too Hot.

Quote:
Originally Posted by Cheechako View Post
Is there much water going into the exhaust? regardless of engine temp, I would think the exhaust would be fine...if it's getting water flow......? Maybe a blockage in the water entering the exhaust elbow? You currently have no exhaust installed as the old one burned up.. right?
It was working fine and then the muffler burnt up and I had to shut it down. I do not know if there was good water flow at that time. I will check that as soon as I can, in the next few days, to see if the hoses, etc. are clear.

I do not have any exhaust hoses installed now so it would be difficult to run it long enough to check temperature, etc.
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Old 02-06-2012, 12:37   #11
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Re: Engine Running Too Hot.

Plastic bags in the water, ( I see them all the time) can get sucked onto the raw intake. Then you loose flow. When the boat is stopped it simply floats away leaving you to wonder what the heck happened...!
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Old 02-06-2012, 12:57   #12
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Re: Engine Running Too Hot.

Quote:
Originally Posted by Cheechako View Post
Plastic bags in the water, ( I see them all the time) can get sucked onto the raw intake. Then you loose flow. When the boat is stopped it simply floats away leaving you to wonder what the heck happened...!
I would second that. You probably have some type of obstruction in the raw water system. Wet exhaust mufflers burn up when they get too hot, not enough water.
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Old 21-11-2013, 10:49   #13
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Re: Engine Running Too Hot.

So, did you ever get this problem sorted out? What was the problem?
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