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· Matt. 5:16
66 Posts
Discussion Starter · #1 ·
I have a 1999 Yamaha SX250TXRY on the back of a 2230 Bay Stealth. My manual says that the maximum RPM should be 5500 and average should be 4500. When I fist purchased it about 4 years ago, I could run at 4500 rpm and get about 38 mph. If I ran at 5500 rpm, I could get about 45 to 50 mph. About a year ago, I had some work done on the lower unit and ever since, I have to run at 5500 rpm to get 40 mph and upwards to 6500 rpm to get anywhere close to 45 mph.

Could something have been done wrong in replacing the gears in the lower unit to increase my rpm and respectfully lower the mph? I thought that maybe the propeller bushing needed to be replaced as maybe the prop was spinning slower than the shaft. However, I had the bushing replaced, tried it out at Fayette yesterday and still the rpm is high with the mph low.

Does anyone know of something else I should be looking at? Also, what is the respective rpm to mph? Maybe I am within the tolerance and I don't know it.

Another issue came up yesterday that I have never had. The engine, since the day I bought it, has with the turn of the key, immediately jumped to attention and purred like a kitten. There is no hesitation ever. However, at the lake yesterday (the first time I have it on the water since the storm), I turn the key and it cranks once, then humms and then dies. After a few minutes of that, it finally cranks up and runs with an attitude. I quickly kicked it in gear, gave the gas and she ran like a champ - to about 4500 rpm - and then the engine just shut down. It ran great at 4000 rpm, but when at 4500 rpm - the engine shut down (stopped running) immediately. I have never had a problem like this and was wondering, with all the wind blowing around (my boat was unscathed from damage) but was left outside in the elements.

Any ideas on what may have happened that caused the big change in engine performance after the storm that was never there before the storm? Any help from my fellow boat experts would be greatly appreciated.

Thanks for your response.

· Registered
2,325 Posts
If you changed the prop this may be where the prob lies..

I would pull the plugs and do a compression test to see how close they are to original specs and how close they are to each other at this time..

Prob may also be with carb adjustments, change in fuel, fuel filters, worn out plugs, etc...

Have you possible changed the height of the motor on the transom via jack plate or using a different tilt position on it now than you did way back when?
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