25 mercury ??

[DUCKAHOLIC]

i have a 25 horse mercury its an early 90's model. it starts and runs just fine and pulls good at about half throttle but once you open it up wide open it bogs down and doesnt rev anymore. i had the fuel pump rebuilt not long ago, carb rebuilt, new fuel lines and filter, and the reeds were check so all of that should be good. it still has alot of compression.. any ideas what it could be??? it also doesnt idle when its in shallow water mood..Thanks

[boatfixer]

Spark, fuel and compression.

Since you say the fuel system has been re-done and you have good compression, although it sounds like fuel related, I'd look at spark.

I'm not trying to tell you this is the problem, but on those, the stator has a high speed and low speed winding. Could be the high side is cutting out. Could also be the switch box. Either case, I'd trouble shoot with a timing light just to find out if its ignition related or not. Run it on the lake with a timing light hooked up and watch and listen.

[DUCKAHOLIC]

thats what i was thinking that it is the high-speed winding is cutting out.. how do i check that? is that part expensive? thanks

[marine_man]

i had the fuel pump rebuilt not long ago, carb rebuilt, new fuel lines and filter, and the reeds were check so all of that should be good.

Was all this work done last year? Did you run fuel stabilizer through your motor prior to putting it away for the winter?

marine_man

[DUCKAHOLIC]

it was done two years ago. yes i ran stablizer threw it before it was stored. it has been doing this for a long time i just never went over half throttle but im going to canada now and i want it fixed.

[marine_man]

If that's the case then I'd say it's time to pull out the timing light and see what's going on.

marine_man

[DUCKAHOLIC]

what should i be looking for? does it sound like the timing isnt advancing enough?.. any idea how much a new stator would be? Thanks!!

[CAMAN]

Had to get the stator replaced in a late '80s 25 merc about 10 years ago. Cost around $200. Would have done it myself but didn't have the proper tools to pull the flywheel.

[boatfixer]

what should i be looking for? does it sound like the timing isnt advancing enough?.. any idea how much a new stator would be? Thanks!!

I'm sorry!!!

When the engine starts cutting out, look at the timing light to see if the light goes out. If it does, then you know its ignition related. If it stays on, then we go a different direction. I can walk you through testing the stator once we get there.

[DUCKAHOLIC]

ok i will get a timing light from my buddy tmrw and see what happens

[DUCKAHOLIC]

ok so i ran the motor with a timing light hooked up. once i got over half throttle the spark was still there the engine just bogged and doesnt speed up any like it always has... what should i do?

[boatfixer]

There is definitly a fuel retriction somewhere. When you throttle back, does it run just fine or die? If it dies what do you do to get it restarted?

If it runs fine then it could be....

restriction in the high speed jet

air leak in the fuel line

incorrect float level

fuel pump

restriction in the fuel line(pick up in the tank)

My first thought would be dirty carb.

[marine_man]

I agree that it definitely sounds like a fuel related issue.

What happens if you close the choke when it boggs down.. does it pick up?

marine_man

[DUCKAHOLIC]

sometimes it will die when i throttle back sometimes it will stay running.. i tryed screwing with the mixture screw last yr set it as rich as it would go and didnt make a difference just smokes like crazy. the carb has been cleaned many times all the lines were replaced the spark plugs are dark like it is running rich. i have never tried choking it when it bogs out? like i said before all the lines, filter, pump was rebuilt, plugs were all replaced as well as the fuel tank.. im lost???

[fatfinger]

i have had similar issues with my 25 merc.luckily,i only had a bad tank and or hose.changed em both out & now shes good to go.i would at least try a different hose + tank just in case.new stuff can go to pot too.just my 2 bits.good luck.

[DUCKAHOLIC]

any ideas on what to do?!?

[Ice Wolf]

Do an compression test to make sure it is not piston or ring related.

[DUCKAHOLIC]

well i ran it today still does the samething and now its leaking oil&gas from someplace idk... im kinda starting to think about giving up on it and getting a different one... any suggestions on a 25horse motor that would be good for duck hunting and fishing?

[DUCKAHOLIC]

????

[boatfixer]

Can you see where it is leaking from?

[DUCKAHOLIC]

nope...

[311Hemi]

So the carbs have been cleaned this year?

Is the fuel bowl staying full when it starts to cut out?

[DUCKAHOLIC]

yes they have.. i cant tell if the bowl is full when it bogs.. but its like washing the spark plug off. where the porsilin was black before is white now seems like its burning really rich at idle

[311Hemi]

If the carb and all the little holes/passages in it were cleaned good, the the gaskets replaced then you should be able to rule that out.

It has a little plastic fuel bowl on the front of the engine under the cowl, correct? Just run it with the cowl off and watch it. I believe you said the fuel filter was replaced, and the o-ring on the fuel bowl as well?

If the plugs are white I would say it's running really lean. Rich at idle should give you black plugs.

Have you check the compression?

That should be a pretty bullet proof engine once you get it figured out. We have an 85' 20hp that still runs great, but have had issues in the past that have required carb rebuilds, new hoses, o-ring on fuel filter, etc.

[DUCKAHOLIC]

yes i know white means lean.. but it was soaking wet which is why i thought it was pouring the fuel in? i could be wrong tho..the compresson is good yet i believe. there is alot when i pull on the cord but ill do a actual test this weekend... im so lost everything on the fuel system has been replaced.