Merc 60 Bogging down

I have a 2008 4 stroke Mercury 60 bigfoot on pontoon boat. When I attempt to go full throttle, it will run fine for a few seconds and then start bogging down and/or lose power. It started doing this late last summer and I looked at it for a couple weekends and then gave up.
It has new fuel pump and new filters. I'm out of ideas other than it might be the VST pump. any help???

 

Since you replaced fuel pump and filters you may as well check and change if old fuel lines from tank to fuel fit filter to engine. Cracked brittle fuel lines with a pin hole may cause air to seep in and cause engine to loose power. While your at it check the lines inside motor won't hurt to make sure there are ok.

 

Definitely sounds like a fuel restriction. How's the vent?

 

I had an older 2 stroke that did that and it turned out to be a cracked coil that powered one of the spark plugs.

 

2004 75 hp merc problem

I just bought a 2004 fisher boat with a 75hp merc on it. I brought it out for the first time and when I give it full throttle it's acting like it's only at half throttle and won't rev higher. I think the over heating alarm was beeping at me too while I was out. It's currently at a shop. They have got a carb kit and changed the fuel pump and supposedly checked it over but they can't figure it out and this is After 8 hours of labour at 120$ a hour!!they haven't even fixed it and I owe them a small fortune. What could I tell them to check next???

 

Both of you welcome to the forum.

Derek, if you have tell the tech what to check next, you're not dealing with a real tech. An overheating alarm is an obvious indication of just a few possibilities, all of which are simple enough to check, typically within a 1/2 hour. Fuel delivery is a different set of issues and you likely have problems in these areas too, which isn't unusual. Commonly they are handled separately.

As to the first poster, when a fuel system gets some age on it, the wise thing to do is renew the lines, all of them. Fuels now will break down the lines, from the inside out, so they look fine, but internally they're shedding bits of rubber, which can play havoc with a fresh tune up or carb rebuild. The best choice is to just pull it all out, clean everything and install new lines, filters, etc.

I too, like Sam, think it might be an ignition problem. There are simple checks for this and a 1/2 hour (again) of investigation can sort out these problems easily, given someone that's familiar with the engine. If they're not accustomed to this particular engine's traits, it'll be a "hunt and peck" approuch, until they stumble on the problem(s). Do you have the manual for this engine? If you don't this is the next part you should buy for your boat. When you get it, run through the standard diagnostic procedures for the systems you think are troubled.

 

Yes, it is making life difficult to not follow troubleshooting procedures laid out in the workshop manual, and having a few basic tools, including a multi-meter.