40 Mercury no acceleration. Boggs in rough water

[Merc40fisher]

Hey guys, I have a 2004 40HP mercury 2 stroke 3 cylinder. It was my grandpas old motor that he's taken out literally 7-10 times. It's been sitting since 2010 so I changed all fuel lines in boat and motor, cleaned all the carbs and changed fuel filter and spark plugs. But after all that it has no power on acceleration untill the boat gets on plane. It's on a 16x48 flat bottom with a couple aluminum decks welded in, nothin too special or heavy. It's as if your running 1/4 throttle untill it gets on plane then starts to take off. No power under load I guess you could say. It also drops about half power when crossing another boats wake or hitting a light chop. Any ideas on where to start diagnosing?? Starts perfect, low, mid, and top end runs perfect..... Just acceleration and the loss of power hitting waves. Thanks

 

[Yesterday]

Re: 40 Mercury no acceleration. Boggs in rough water

It sounds as though it's not enough motor for the boat and you may be over-prop'd for your setup. When you say 16X48 you mean feet???
Some thing's not making sense about those dimensions. What is the max RPM you're seeing at full throttle?

 

[Merc40fisher]

Re: 40 Mercury no acceleration. Boggs in rough water

16 feet with 48 inch wide bottom. I do need to reprop I believe. I'm turning 5800. Should be 5500. I got a 12 pitch now, but wouldn't a 13 or 14 make acceleration even slower?

 

[Yesterday]

Re: 40 Mercury no acceleration. Boggs in rough water

16 feet with 48 inch wide bottom. I do need to reprop I believe. I'm turning 5800. Should be 5500. I got a 12 pitch now, but wouldn't a 13 or 14 make acceleration even slower?

Yes you'll loose a bit on the hole shot but I'd only upstep 1" pitch. It won't make much odds overall though.