2003 5.0 mercruiser lost 600rpm overnight

[Bill64]

5.0 2bbl carb ran fine last weekend, take it out this weekend and it starts and idles as well as ever, give it the gas and you can feel a 20% power loss from the holeshot to wot. Wot was about 4600 and now about 4000 rpm. The one thing I done was put in 10 gallons of gas from a very busy gas station. The next day I added another 10 gallons of premium from another gas station with no change. To me it feels like a timing issue because it runs smooth, no

 

[dingdongs]

change fuel filter then get back to us.No miracle cures if you haven't done this.

 

[wellcraft-classic210]

I agree with dingdongs that its probaly a fuel supply issue and the Fuel filter is the ist place to start.

Also If any debris gets into your fuel tank it can lodge in the barb fitting leaving your tank which has a check valve in it. That will in turn restrict flow also.

Using a funnel with a screen is cheap insurance to help avoid that problem.

 

[alldodge]

I think it's a fuel issue, but when was the last check or change of the outdrive gear lube?

 

[Bondo]

5.0 2bbl carb ran fine last weekend, take it out this weekend and it starts and idles as well as ever, give it the gas and you can feel a 20% power loss from the holeshot to wot. Wot was about 4600 and now about 4000 rpm. The one thing I done was put in 10 gallons of gas from a very busy gas station. The next day I added another 10 gallons of premium from another gas station with no change. To me it feels like a timing issue because it runs smooth, no

Ayuh,.... That's not overnight, that's a Week later,....

Is this a Dock boat, moored all week,..??

 

[Bill64]

I have replaced the canister fuel filter at the end of every season but will do it again and as far as the oil in the outdrive goes last year with water levels down my ss prop hit a rock and my insurance paid for a new lower end and went back to aluminum prop. broke in new outdrive, changed gear oil in july and once again at end of season. this weekend I will change filter and replace anti siphon valve. Thanks for your interest!

 

[airdvr1227]

I had a non-cooperative bilge pump that I was unaware of except for the fact that it felt like I was towing the Edmund Fitz. Make sure you're not carrying unneeded liquid weight in your bilge.

 

[NHGuy]

Dump out the fuel filter contents to a glass jar and let them settle. Good evidence.