2003 115hp Mercury 4-Stoke

[golden eye]

I have a weird problem with my motor. I've had the boat a year, It starts and trolls perfect with no problems and runs fine after it gets up on plane but it don't have any take off power and when i go to put it on the trailer i can give it full throttle and it don't have enough power to push it up on the trailer. It had a 13" prop and i was told to put a 15" on it so i did and that hasn't helped at all. Its in mint condition i always change the oil and plugs no matter what. I'm at a lost cause. Has anyone else had this issue if so please let me know. Thank You. I have also put all new fuel in it plus new fuel filter and put 91 octane in the tank plus i always run stabil in every tank.

[x4flatfish]

Need to know what boat this is on? Also you say a 13" and 15" prop. Are you talking about diameter or pitch? Going up in pitch will hurt low end as will going to larger diameter. Need more specific info on your complete setup to help you figure this out...

[DW]

If it revs up without power the cause is a spun prop which requires hub repair.

[tonto]

He changed the prop so it’s not a bad hub. Sounds like maybe the motor is not running on all cylinders.

[Eyecatcher23]

Originally Posted by tonto

He changed the prop so it’s not a bad hub. Sounds like maybe the motor is not running on all cylinders.

I changed props once and had a similar problem afterwards. It turned out I forgot to take the old thrust washer off the shaft before putting the new hub kit on. The results of having the old and new thrust washer back to back made it act like a spun hub but not constantly. Not one of my finest moments behind a wrench.

[Tim_Kelly]

If the boat runs normally otherwise, but is struggling when you try to get on plane or to push the boat up the trailer, it sounds like the prop is cavitating. Odd that it's done the same thing with two different props though?

[Bobby Winds]

Is this a old carb outboard, if so you might have some carb problems that probably stem from Ethanol gasoline. A rebuild of the carb AND replace all the gas line hoses including bulb because it sounds like that engine is starving for gas.

You could just change out the gas lines and see if that helps at all but usually those carbs are gunked up from many years of Ethanol gas being used.

If it's not a carb outboard I would be looking at electrical problems like coils, etc......

[golden eye]

Thanks for all the input from everyone. This is why i like the website. my prop is now a 15 pitch from a 13. I personally dont think this is the problem. I did replace most of the hoses and they had started to separate due to old gas i would assume. As far as the thrust washers i didnt even think about that. I have changed alot of props and have never had this issue.It is on a 17FT aluminum Deep-V Smokercraft

[nebrwalleye01]

Almost certainly fuel filters. Dont know about your Merc, but my Yami has multiple fuel filters. Had same problem changed them all ran like new. Costly to change them.

[man164]

I would think a 17 ft Smokercraft with a 115 hp should be turning a 17 pitch prop. I think a 17 pitch Spitfire should be just about right.

I would start with a general tune up.

New plugs, change fuel filters. How old is the fuel line? It could be becoming separated and the liner is causing a fuel supply problem.

When you changed props did you use the same hub insert or did you install a new one?