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Outboard Motor Experts...
Posted on 7/11/20 at 3:26 pm
Posted on 7/11/20 at 3:26 pm
Yamaha made some of the most durable motors with the 90, 85, 75, and 70 hp 2 stroke inline 3 cylinder engines some would say.
Why did they go to a V4 for the 115 and 130 hp engines? Seems like adding a cylinder to the top or bottom of the inline 3 would have been a better design for them and cheaper to make since having 1 less head and a one piece gasket for instance. I remember Suzuki and Tohatsu making inline 4 115s and Suzuki had a 140 inline 4 cylinder 2 stroke.
Was just wondering as I seen an older Yamaha V4 115 pass down the canal today...
Why did they go to a V4 for the 115 and 130 hp engines? Seems like adding a cylinder to the top or bottom of the inline 3 would have been a better design for them and cheaper to make since having 1 less head and a one piece gasket for instance. I remember Suzuki and Tohatsu making inline 4 115s and Suzuki had a 140 inline 4 cylinder 2 stroke.
Was just wondering as I seen an older Yamaha V4 115 pass down the canal today...
4
Posted on 7/11/20 at 3:29 pm to GoAwayImBaitn
Torque plain and simple.
Posted on 7/11/20 at 5:06 pm to GoAwayImBaitn
Because that’s how the evinrude motors that they copied were built.
Posted on 7/12/20 at 7:22 am to GoAwayImBaitn
On a similar vein, I’ve been researching the 4 cylinder four stroke Yamaha and Suzuki engines for a possible retrofit on my boat. It’s amazing the power being squeezed out of increasingly smaller motors
Posted on 7/12/20 at 8:15 am to GoAwayImBaitn
quote:
and cheaper to make
I dont think so. Your logic is good with one less head, but the bottom end of an inline has more bearings, a longer crank, longer block, etc. I dont think theres too much appreciable difference in the overall build cost.
I think it has more to do with overall power density. You can cram more HP under a smaller cowling with a high revving V engine, I dont think the overall trend is much more complicated than that.
Some other possibles,: Once the power started getting far beyond 115 the blocks get taller and more difficult to cool upper cylidners. They also need to be heavier built as they get taller since gyroscopic forces increase the higher up you put the flywheel. Probably some torsional vibration problems as well since outboards dont have viscous dampers and inlines tend to be more torsionally abusive than V engines.
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