Boat only goes 10mph

[Ketchum82]

I am a first time boat owner and know very little about them. We have a used 2010 Tahoe I/O 225 deck boat with a mercruiser 5.0 mpi engine. Yesterday was about the 5th trip out on the water. The boat has only ever gone a little over 40mph since we bought it which seemed a little slow for the make and size. Anyway, we were cruising nicely and as the day went on, we started to lose speed to the point I couldn’t even pull my kid on a knee board. We loaded up after we were pegged out and only going 10mph. It was not over heating or having trouble starting or idling and everything sounded great. Being “boat stupid” I don’t even know where to start. Any suggestions would be appreciated.

 

[wellcraft-classic210]

1 suggestion -- Tell those kids to get paddling :joyous:

Seriously
Were able to listen to the motor sound & monitor RPM's ? // That would help determine if its engine related.

 

[Scott Danforth]

welcome aboard

start with the basics...... the DIY stickies on low WOT at the top of the mercruiser forum

check your fuel filter contents

 

[KD4UPL]

I'll guess you spun your prop. Have you run aground or hit anything floating in the water?

 

[nola mike]

Spun prop would raise rpms without moving the boat...

 

[Bondo]

I am a first time boat owner and know very little about them. We have a used 2010 Tahoe I/O 225 deck boat with a mercruiser 5.0 mpi engine. Yesterday was about the 5th trip out on the water. The boat has only ever gone a little over 40mph since we bought it which seemed a little slow for the make and size. Anyway, we were cruising nicely and as the day went on, we started to lose speed to the point I couldn’t even pull my kid on a knee board. We loaded up after we were pegged out and only going 10mph. It was not over heating or having trouble starting or idling and everything sounded great. Being “boat stupid” I don’t even know where to start. Any suggestions would be appreciated.

Ayuh,..... Welcome Aboard,......

What were yer rpms at Wot, at the low 40 mphs,..??

What were yer rpms at 10 mph headin' to the dock,..??

Rpms at Wot should be 'bout 4800 rpms to get the Most outa yer boat,.......

The rpms at 10 mph will determine where to look for the Problem,......