Mercruiser 496 Mag hesitation on top end
 

Hey all,
I have a 2001 Z275 Shabbah with mid-cuddy, and am running a Mercruiser 496 Mag with a Bravo III outdrive. Suddenly I have a slight problem that I need some help addressing. The boat comes out of the hole without a problem. I can hammer it, get on plane, then run for a bit without an issue. However, once it gets on plane and I start to trim up/throttle back, the motor has a hesitation to it. It seems to happen at about 3/4 throttle, so I'll ease off of it and throttle back into it then it runs fine and eventually does the same thing. It seems to act like a fuel-related problem, so I changed the water/fuel seperator and ran seafoam thru the tank. However the problem is still there? Any suggestions on what else I can try?
Thx,
Tony

Re: Mercruiser 496 Mag hesitation on top end
 

I had a problem where it would run fine then just die. turned out to be a loose ground on the slave solinoid. check your connections. you can also check the anti-siphon on the gas tank. there is a screen on it. maybe a tune up??

Re: Mercruiser 496 Mag hesitation on top end
 

Thanks for the info...I checked what I could and gave in...it's at the shop today but my mechanic takes care of me and I'm sure I won't have any bogus charges. I appreciate the reply!
Tony

Re: Mercruiser 496 Mag hesitation on top end
 

Hi Tony
Let us know what your mechanic finds that was abit of a toughy I was asking around with some of the guys around here no one had a good answer for it.

Re: Mercruiser 496 Mag hesitation on top end
 

Will do...

Re: Mercruiser 496 Mag hesitation on top end
 

After I took the boat to the shop they of course hooked their computer to it and found voltage error codes. Apparently my alternator was putting out about 13.2v and the 496 motor with 3 batteries on an isolator needs at least 14v. They sold me an alternator and we went on a test run after it was installed. The tech again hooked the computer up and of course it ran fine while he was on the boat. Took the damn thing out yesterday and it started hesitating again! I think it is a combination of the bad alternator that I had and also the batterires may need replaced. Of course the boat didn't have a problem while the mechanic was riding with me...figures. I'm going to put some batteries in the tihing and will let you know how it goes...:(

Re: Mercruiser 496 Mag hesitation on top end
 

Isn't that always how it goes I have been on both sides of that fence people bring me a car say its doing such and such we go for a drive nothing, they leave and call 3 blocks away say it's doing it again. Bring it back and there it is change part out and it's fine for a week then another issue. Have taken my vehicles in hooked to comp get all the codes change some parts fine for a day and bam codes everywhere again Good luck keep us informed.

Re: Mercruiser 496 Mag hesitation on top end
 

Ok, sorry for delay but been really busy. I replaced the alternator, a bad battery, and ultimately found that my fuel pump was going out. This of course was a job I wasn't going to tackle because the motor had to be pulled. So after all that, which I'm sure my alternator was bad and I needed a battery anyway, it was the high pressure fuel pump and ended up running my tab up a little. Oh well, she runs great now though!!!! Thanks everyone!