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IO Engine RPMbs

ehlien

Regular Contributor
I have a 454 Merc IO in a 28&#

I have a 454 Merc IO in a 28' Baja with a 21 pitch SS Mirage prop. Last year I had the stern drive redone. As this year has gone on I have found the engine RPM starting to rev higher particulary when I start the day off or it fluctuates significantly as I drive. At this point I have to get to 4500 RPM to do the speed I used to at 3500 and no way it will stay under 5000 at 3/4 throttle. Sometimes after I have been out running a while it seems to stabalize back down. The boat is stored in the water usually with the drive in at least the partially up trailer position. So what's up with this? What are the rpobably causes and solutions??
Thanks!!
 
"[b]"What are the rpobably

""What are the rpobably causes and solutions?? "

Probably a Dirty Bottom,......... Clean it......"
 
"cleaning it off could help it

"cleaning it off could help it out alot. I can see if you have not cleaned it in a while, the build up could be alot. THis could absolutley cause this to happen. This could be an easy fix"
 
"At this point I have to g

"At this point I have to get to 4500 RPM to do the speed I used to at 3500 and no way it will stay under 5000 at 3/4 throttle."

Does your prop have a rubber hub? May want to check this as well.
Kurt
 
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