Low rpm’s on 2007 Mercury 60hp EFI at WOT

[WICKER55]

I have a 16 ft Legend Xcalibur with a 2007 60 Mercury hp EFI with 12p prop. Used to run at 5800 rpm’s at WOT at 30mph. A week ago it ran fine but could only get the rpm’s up to 5000 At 25 mph. I decided to change out the fuel filters, oil filter and oil and spark plugs. Started it up in the driveway and it just purred. Took it to the lake and it started fine but the rpm’s only went to 4200 at WOT and 22 mph. Turned back to harbour and it was even lower. Throttled down and headed home. I did feel the tell tale and it was good flow and quite cold.

 

[WICKER55]

Also thinking, could a bad seal in the trim piston be causing this by not allowing me to get right on plane?

 

[Dave1027]

The main difference between purring in the driveway and trying to get on plane is a lot more fuel needs to be supplied. I'd be looking at the fuel pump.

 

[pwiseman]

Any chance your weight changed? A few hundred lbs would make it harder to plane and keep your RPMs lower than max. I had a 16 footer and would end up using 2 props. One for fishing 3 people with livewells full and one for lighter loads. needed to step down a pitch when loaded to plane out properly. Based on fact that you are running a 12P with 60 HP, I am going to assume this is a heavier 16 footer.

 

[WICKER55]

It is a heavier 16 ft (100 gage aluminum). Weight is same as it was a month ago when it was running perfectly. The trim/tilt on this unit has only one piston. The tilt function works perfectly. Is it possible that the trim function can fail under load but the tilt work as normal.

 

[pwiseman]

It is a heavier 16 ft (100 gage aluminum). Weight is same as it was a month ago when it was running perfectly. The trim/tilt on this unit has only one piston. The tilt function works perfectly. Is it possible that the trim function can fail under load but the tilt work as normal.

Gut feel is 60 HP should be enough to plane out a 16 footer without any trim unless is over 2000 lbs or maybe more than that. Seems like that would be well over typical though. I suppose it could be your tilt/trim not performing with load, but have not heard of that before.