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<blockquote data-quote="FuzzyGrub" data-source="post: 212379" data-attributes="member: 3438"><p>I would go a step further and say there might not be any general rule to follow. Below are the SM specs for 2 stroke Nissan/Tohatsus:</p><p></p><p>Model kPa psi</p><p>2.5-5 hp 539 78</p><p>8-9.8 hp 392 57</p><p>9.9-18 hp 760 110</p><p>25-30 hp 755 110</p><p>40 hp 735 107</p><p>40-50 hp 670 102</p><p>60-70 hp 833 121</p><p>80- 90 hp 804 117</p><p>115-140 hp 882 128</p><p></p><p></p><p>Specs from Merc SM for 20 & 25HP:</p><p></p><p>Each cylinder within 15%, and less than 120 psi may indicate worn engine.</p><p></p><p></p><p>Out side of the basic displacement to head volume compression (static), you have to take in consideration the height of ports for dynamic compression. </p><p></p><p>I 100% agree on keeping a yearly record. While I have been good on doing that on my I/O, not so much with my 2 strokes.</p></blockquote><p></p>
[QUOTE="FuzzyGrub, post: 212379, member: 3438"] I would go a step further and say there might not be any general rule to follow. Below are the SM specs for 2 stroke Nissan/Tohatsus: Model kPa psi 2.5-5 hp 539 78 8-9.8 hp 392 57 9.9-18 hp 760 110 25-30 hp 755 110 40 hp 735 107 40-50 hp 670 102 60-70 hp 833 121 80- 90 hp 804 117 115-140 hp 882 128 Specs from Merc SM for 20 & 25HP: Each cylinder within 15%, and less than 120 psi may indicate worn engine. Out side of the basic displacement to head volume compression (static), you have to take in consideration the height of ports for dynamic compression. I 100% agree on keeping a yearly record. While I have been good on doing that on my I/O, not so much with my 2 strokes. [/QUOTE]
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