Props and Cooling

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Clay Gurnett

My 18hp Yanmar seems to always overheat if I try to cruise it above 2500 RPM's - Is there anything that can be done to improve the cooling system to allow for running the engine a little harder ??? In addition, the cruising speed under power seems weak...Has anyone fooled around with any different props / pitches to improve cruising speed ??? These two questions are somewhat related as I need the higher RPM's to achieve the higher speed with my standard issue prop. Thanks.
 
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Alex

It nappened to me too..

If you have the "extra" 3 blade (very wide blade)15 inch diameter cruising prop, in warm water ,with prolonged high 2800+ RPM , it might just happen occasionaly .Reduce the pitch to 9 (if you have 15 for diameter), but make shure you have checked before that the other options, like clogged cooling-water ways .
 
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Jim McCue

Overheating

I have the 2GMF Yanmar 13 HP. You may want to pull out the heat exchanger on the top of the engine and clean it up. You may need to buy two gaskets before reinstalling. I cleaned mine out after several years to find some accretions but not much growth in the exchanger. Used a little Lysol Direct and pipe cleaners.
 
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Russ Garecht

The obvious

First check the max RPM of the motor. I think, but I might be wrong, that it is only 2500 RPM. I was also having overheating problems. Checked the filters etc. and found nothing restricted. Even replaced the pump impeller. One day while scuba diving under the boat I took a piece of 1/4 in rod ran it in the through hull. The amount of marine life I killed was amazing. Now after I clean the strainer I open the valve and make sure I have good flow. Hope this helps. Russ Garecht Her Diamond Ring
 
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Robert Kernodle

Check the elbow

I have a 24 hp Yanmar and cleaning the heat exchanger was not enough. I had to have the exhaust elbow taken off and flushed out with muratic acid. I am not sure if the 18 hp has the same exhaust configuration as the 24 hp but I would be willing to bet it is similar. Prior to having the elbow removed and flushed I was running hot at 2500 rpm. You can tell by watching he water exhaust if the elbow may be clogged. Before the elbow was cleaned I could tell a noticable pause in the water exhaust cycle. After cleaning, every cycle produced water. Good luck, Robert Kernodle Vison 32 - Mary Lynn
 
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Robert Kernodle

Check the elbow

I have a 24 hp Yanmar and cleaning the heat exchanger was not enough. I had to have the exhaust elbow taken off and flushed out with muratic acid. I am not sure if the 18 hp has the same exhaust configuration as the 24 hp but I would be willing to bet it is similar. Prior to having the elbow removed and flushed I was running hot at 2500 rpm. You can tell by watching he water exhaust if the elbow may be clogged. Before the elbow was cleaned I could tell a noticable pause in the water exhaust cycle. After cleaning, every cycle produced water. Good luck, Robert Kernodle Vison 32 - Mary Lynn
 
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