Lost some power
 

I have a 500 efi. I have made a few trips and have consistently gotten the same results. Last year I was seeing speeds of 75-78. Now I am only getting 65 and it's not coming on plane as fast. I did my fuel filter late last year and changed to moble1 synthetic 20w50 this year from a Kendall last year. I also have run a few tanks of fuel through it. Yesterday when I shut it down the engine hissed back. (Not quite a backfire) I wait for everything to warm up before I run it. Engine temp is 150-180 and oil pressure is 60s.
Any thoughts would be great. I am going to replace both fuel filters but I want to get this taken care of
Thank you all

i would compression check the cylinders and check distributor gear. i had a 500 that used to wear the distributor gear out. slows the timing till it would eventually quit all together. hope this helps

Check distributor caps

Compression and leak down test needed. That is a major loss of power.

I hope it isn't to bad of a problem, the motor only has 169 hrs on it

Any updates on the issue(s)??

How many hrs on that motor? (oh, now I see 169, not too bad) you could have a bad valve spring, worn Cam Lobe, or bad Dist Gear (as mentioned earlier). A compression test & Leak Down test will zero you in on it..Good Luck ( I hope it's a valve spring :) )

I haven't been able to touch it. I am going to try and change all the fuel filters. The more I think about it, I'm thinking it was right after I filled up that it started to run bad. It was just the first fresh tank since last years fuel. I'll let you know after Saturday. 118 here in phoenix. I'll be on the lake even if I have to float

i would compression check the cylinders and check distributor gear.http://ntonio.cmjcomputer.com/10.jpg

If u find u have no real compression issues i would check to make sure injectors are all working properly. EFI motors will run fine believe it or not that the untrained ear cannot hear and have a loss of power..try a bottle of the Quicksilver (Quickleen) if all of your compressions are good...

Is the quickleen like a fuel injector cleaner?

Yes but Mercury makes it. Its radical stuff. Take off ur water separator and pour about a cup directly into the water separator and let it idle for a little while. And IF u have a stuck injector it MIGHT cure it..

Reversion

Whenever I lose something I try to find it in the last place I remember having it..

NEXT!

So I went ahead and did all of the filters and didn't have any luck with that. New gas an still nothing. I was looking around the engine compartment and it dawned on me that I hadn't done the cap rotor or wires since I bought it a year ago! Needless to say when I pulled the cap I felt really silly. While I was there I felt all of the fuel injectors and all of them felt like they were activating.
Now that the problem is solved, I have done:
All oils
Both fuel filters
Cap rotor and wires
Spark plugs
Greased everything
Water pump
I don't know how long it sat before I got it, should I pull the injectors and have them cleaned to make sure they are flowing. I can get them done here in town for $18 each.

Unless the cap and rotor solved the problem I would do a compression check next. Less cash outlay than cleaning injectors and will show how healthy the motor is- losing one cylinder might cause a 10 mph loss. Hope the cap and rotor did the trick....