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1980's Johnson/Evinrude 20/25hp conversion to 30hp with pics
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<blockquote data-quote="dandrews" data-source="post: 490682" data-attributes="member: 31887"><p>Just purchased a new to us rig this past week, 1984 Lund s14 dlx with a 1985 Johnson 25HP tiller, first time looking at this motor. I’m no stranger to aluminum boats, involved with hydroplane racing on the side and know enough to be dangerous. So I will beat on this topic some more and provide some more insights. Touching on the last post early 35’s (1980-83 I believe) ran a 1.93:1 gear that’s why you will see 11X9’s and 10’s on those engines. Haven’t seen any mention of total timing advance, not much talk about reed stops and finger reeds and the all important tuner pipe between the differently rated HP variations of the 31.8 block. If anyone is going to go beyond the scope of switching out parts on these engines I strongly suggest you read up on Gordon Jenning 2 Stroke Theory before you start modifying ports, heads, intakes etc. Have a clearly defined goal of what you are trying to achieve with the engine/boat setup. In my case with be looking for more low, mid and top end gains without sacrificing low speed trolling capabilities. Will achieve this through parts swaps, prop/setup and possibly some exhaust side modifications.</p></blockquote><p></p>
[QUOTE="dandrews, post: 490682, member: 31887"] Just purchased a new to us rig this past week, 1984 Lund s14 dlx with a 1985 Johnson 25HP tiller, first time looking at this motor. I’m no stranger to aluminum boats, involved with hydroplane racing on the side and know enough to be dangerous. So I will beat on this topic some more and provide some more insights. Touching on the last post early 35’s (1980-83 I believe) ran a 1.93:1 gear that’s why you will see 11X9’s and 10’s on those engines. Haven’t seen any mention of total timing advance, not much talk about reed stops and finger reeds and the all important tuner pipe between the differently rated HP variations of the 31.8 block. If anyone is going to go beyond the scope of switching out parts on these engines I strongly suggest you read up on Gordon Jenning 2 Stroke Theory before you start modifying ports, heads, intakes etc. Have a clearly defined goal of what you are trying to achieve with the engine/boat setup. In my case with be looking for more low, mid and top end gains without sacrificing low speed trolling capabilities. Will achieve this through parts swaps, prop/setup and possibly some exhaust side modifications. [/QUOTE]
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1980's Johnson/Evinrude 20/25hp conversion to 30hp with pics
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