1971 Evinrude 25 horse no power under load at high throttle

Joined
Apr 21, 2008
Messages
10
Hi all. My little Evinrude 25 stopped giving me power at high throttle suddenly a couple days ago. It starts and idles like a champ, all day long, and will push the boat (12.5 foot aluminum floor inflatable) at idle or up to about 5 mph but that is all. The motor will rev up but will not push the boat any faster. Normally this motor planes this boat just fine to an easy 20mph. Reading similar posts suggests to me that it could easily be a carb problem, maybe a clogged high speed jet? I have not rebuilt the carb recently. I want to get some thoughts though because I recently replaced the prop and drive pin (9 x 10.5 prop) and my first thought was that it was a prop problem, though I did remove the prop on the water and the new prop and pin look fine. Also was using a new fuel hose at the time (second use). The boat was running and planing fine for a while then we accidentally hit a shallow sand bar in the water (at low speed) killed the motor and stopped on the beach for a while. No high speed after we started again and none since. Any thoughts?
 

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Sounds like when you hit the sand bar you spun your prop. Take a sharpie and draw a line from the hub to the prop. Run it and I bet the line no longer lines up. If the engine will rev in gear and you go nowhere 95% of the time it has been a spun hub. If you have a known good prop put it on there and try it.
 
Joined
Apr 21, 2008
Messages
10
Thanks, the plugs were new a month ago but I will check for spark. I thought first about the prop but this is a pin drive prop, so unless I am not understanding there is no hub to spin. Both prop and pin look fine, no cracks, no worn areas on the pin, pin is straight.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,043
You are not understanding the bit about the prop being spun.----I used to have a prop cut apart to show to the doubters who said---" There is no rubber hub in my prop "---And report if the spark on your motor can jump a gap of 1/4" or more.-----Saying that you think you have spark is not a good answer !
 

kbait

Commander
Joined
Nov 13, 2007
Messages
2,446
Drive pin connects to prop hub, and that hub connected to the metal blade part of the prop by a compressed rubber bushing. The bushing can lose its bonding strength, and slip under load. So, when powering up in gear and rpm's increase while mph decrease..(and not jumping to neutral or any banging), you have a spun prop hub bushing.
 
Top