25hp doesnt seem right

[Cobiasport18]

hello every one i need help i have a 2001 mercury 25 thats just not acting right i bought this motor used and it looks really went taken care of but it lacks power i put this motor on a 13 foot skiff max hp for the boat if im going with the tide and wind planes out fine but comeing back it will not plane out . if i put a cooler in it with ice it will not plane out . at frist i thouht it was a fuel prolem went out bought a new gas tank and everything. did a decrab with seafoam worked better but still wont plane out right im thinking about a carb rebuild just wanna make sure im thinking this out right is there anything that i should check weres the best place to start?

 

[CharlieB]

Re: 25hp doesnt seem right

Verify that the motor is in sound mechanical condition by checking compression on all cyls.

Then verify that the ignition system is capable of throwing a hot blue arc at least 7/16 inch at each plug wire.

Once both are confirmed then it is time to check the fuel system. Disconnect the fuel line to the carb(s) and crank the motor, observe the fuel stream for a strong pulsed flow, a weak fuel stream could be caused by a fuel pump, restricted hoses, fitting, or air sucking into the hoses anywhere before the pump.

Next go ahead and clean the carb, install new gaskets, carb kits are relatively cheap.

Reinstall the carb and adjust the linkage and timing following the directions in the service manual to the letter.

A service manual may be fouund thru link in one of the 'sticky' postings at the top of this forum.

 

[matth121]

Re: 25hp doesnt seem right

not that i have anything to add since my motor is an 82, but mine won't plane at all, at best, i get 4-5 mph at full throttle- problem is, my rpm's never get above 2700 when in gear- i now know this is because my exhaust is plugged, gone, whatever. pipe came apart from the adapter plate- im working on this now, i'm sure your pipe hasnt rotted or come off like mine, but i wonder about your rpms. are you hitting your WOT range? somewhere between 5000 and 6000 rpm, not sure for yours. Is it possible you may have a blokage in your exhaust? I've been told that sand and stuff can get up there as well as cheap oil can gum up your exhaust. Hope this helps, good luck

 

[Star]

Re: 25hp doesnt seem right

I don't want to sound like a smart A---- but you have to be running on one cylinder!!! An old Merc I had made my 14' heavy construction JUMP out of the water!!!

 

[matth121]

Re: 25hp doesnt seem right

lol, no prob, im not though, least not at idle, i can pull each plug wire separately and it'll run on the other with a noticable difference. in neutral, it'll rev much higher, not that i'm free reving the crap out of it, cause i'm not. i was told by a mechanic to cover the above water exhaust port while boat was idling and look for exhaust bubbles coming up from the prop. There were some but it was obviously under way more pressure than it should be, lower unit off, i could look up the exhaust port and see what was left of my exhaust tube poking thru the hole. I'm pretty sure this is my problem, now the power heads off and with adapter plate in hand, i'm going to fab a new exhaust tube and put it back together. And i'm well aware that this motor should haul *** on my small fiberglass boat, hoping thats going to be the end result of all this work i'm doing. Hope im not hijacking this thread, wasnt my intention.
if youre interested, i started a thread called "lower unit removal", the whole story is there
http://forums.iboats.com/showthread.php?t=493439

 

[Cobiasport18]

Re: 25hp doesnt seem right

thanks for the replys i now have a starting point. im gonna check everything charlieB sayed yea it's funny i took it out after i posted the other day it dose plane out i can get her up to 25 mph if im going with the tide no wind but went i was coming back i couldn't get her past 6 mph if i lean forward and move stuff toward the front of the boat sometimes ill get it to plane out going up stream but most of the time i cant im not sure about the rpms. but went i get it to plane out it flys ok im thinking it mite be the low speed jet. but you never know anyway thanks for the help im try to get this baby going