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I need help I have a 25 hp 2 stroke outboard that i cant get to idle. i have rebuilt carb, fuel pump, put on new coils plug wires ect. It shacks be low about 1400 rpm in and out of gear. will the 2 rubber horses from behind carb that go to intake side cylinder's cause this problem it has 100 psi in both cylinders.
Randy
Have you got a strong spark at both plugs. Those older 25 Mercs are notorious for squirely acting switch boxes
Thanks for that info
I'll help walk you through the most likely causes but I have to ask that you proof read your spell check and post your results of what the problem was.
The most likely cause is in the carb. You mentioned that you cleaned it. The carb bowl has an 11mm (7/16) brass cap on the bottom. It has a spring and ball under it. If the ball is missing or has been shoved down into the spring, the engine is receiving too much fuel and can't digest the extra fuel at anywhere near idle speed. Remove carb and check that first
I will do that tomorrow I got motor off boat and in 55 gallon test barrel Thanks for your help
Sliderman I took off carb and unscrew brass plug It holds fuel bowl on carb. There is no spring or ball all i see is the fuel jet
Randy
Wrong cap. That one is 13mm/1/2 inch. The one you need to check is beside it. Give me a year model guestimate.
Its a 1988 25 hp mercury
Ok. Check the smaller brass cap that sits beside the main jet. The ball should be at the bottom with the carb upside down.
Yes your right Thats the the fuel primer. I will check it out tomorrow.
I took off other brass plug and there is a spring and ball. The spring came out first and ball second it was down in carb. every thing was clean. Now where do i look?
Randy
The small brass tube that runs from the bottom of the carb, through the middle of the carb intake and into the top of the carb carries the fuel used for idle and off idle. With the bowl off and the top cover off, remove the idle mix screw and look down that tube from the top. If it's clear, reassemble the carb and set the idle mix screw to 1 3/4 turns out from a lightly seated position.
Did that and every thing is clear. The 3 holes that feed fuel to throttle bore are open also.
Ok, I believe we are through with the carb. I need a pic of the right side of the motor. Also, have you replaced the spark plugs and taken a sample of the fuel to inspect for water?
Its fresh rec fuel and new spark plugs and new fuel tank.
Did the problem begin while out on the water, between trips, after maintenance work etc.?
I just bought it used I was told it ran good but to big a motor for his boat. Ever since I bought it it has had same problem. It will run great top end and mid range but when i try to idle it down it wants to shack and stall. Some times when you try to start is it will rip crank rope out of your hand.
The last sentence holds the key. Like B.B. stated earlier, the switch boxes have a history of acting up on those rigs. If it's ripping the rope out of your hand, it's a timing issue. The potential issue could be a badly advanced base time, switch box or a faulty trigger. Get a pic of the right side of the engine so that I can see what the base timing linkage looks like. If it's not way advanced, you'll either need to put it in the hands of a competent mechanic or start replacing ignition components until you get the failed component out of the system.
A friend of mine has a motor like mine thats a parts motor. Im going to take his switch box and give it a try. Thanks for all the help you guys have give me. I will let you know what happens when I change it.
I would put a timing light on that and see where the base timing is at. A steady 6-8 degrees BTDC at cranking speed is what you're looking for. If it's all over the place, the trigger would be the first thing I'd look at. If it's way advanced, someone has probably cranked the adjustment screw in as far as they could.
I will check that out. Thanks
You ever get that 25 lined out?
I went to try with timing light and having problems just to get it started. I think the switch box took a crap :hesaid
Next step. I pulled both plugs out of motor and zip tyed them against head bolts for ground. took of rewind off motor and put a socket on bolt holding fly wheel on. put socket on bolt and spun it with half inch drill. I have no spark at all now. What do i do now :banghead
Did you have the key turned on? Keep in mind the motor has to turn at least 300 RPM to start.Quote:
Originally Posted by Randy 1
This is a rope start motor. I disconnected the wire to kill switch.
Here is what I did today to the mercury. I pulled off flywheel to try to find out whats going on with problems. Well I think I found out problem. One of the magnets came lose and was out of position. One was at 12 and one was at 7 ;30 . Also I think switch box died.
Randy
I want to thank Barnacle Bill and Sliderman for all your help you have gave me on my mercury outboard. :ThumbsUp
Randy
New switch box installed today and WOW shes alive. Thanks so much for your help:HandsClapping
Randy
Good to hear