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25 hp mercury outboard wont start

kimcrwbr1 said:
Have you done a de-carb? Get a can of seafoam spray and get the engine hot rev it up to around 2000 rpm and spray seafoam into the carb short spurts until it starts to smoke real good and quickly shut it down. Let it sit for 1/2 hour or so then start it and run it around 3000 rpm until the smoke clears out. That will clean the carbon off the rings, pistons and cylinders and you will probably get alot of black crap out the exhaust. If your running in a barrel drain it and refill with fresh water. To check if it helped check the compression cold first, do the de-carb and check the compression again after the engine fully cools down.[/QUOT


I recheck my compression with my buddies better gauge and one of my cylinders was low. I tried blowing smoke in the plug holes and I can see tiny misty smoke coming out of the carb. Do u think i need a reed cage gasket replacment. I heard its notorious for going bad on mercs. Ive never done any major work like this before. Were do i start and what do i need. How many gasket do i need, should i go ahead and replace the piston rings while im at it? Only one cylinders is bad so should i not touch the good one and deal with the bad one. My online manual isnt helping me much and it doesnt show step by step on how to get the pistons out.
Any help would be great thanks......
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kimcrwbr1 said:
There ya go not a job for the novice but can be done. What were the compression numbers you dont have to pull the crank all the way out to pull the reed blocks. for sure you will need a exhaust housing gasket and the two crank seals. The reed bearings split in half you dont need to pull the pistons out if your compression is acceptable. I have taken a new cylinder hone and honed the cylinders and put new rings in if the cylinder walls were just glazed use lots of oil and hone it just enough to remove the glaze. Make sure the reed block fits the crank good and tite. You will know once you get it apart what you will need to get it running good. I would hold off on buying parts before you look at it for parts availability and if it is worth the time and money. Take your time on removing screws and bolts use alot of heat and chemicals dont force nothing broken bolts will make the job alot harder. If you decide to do a complete rebuild start a new thread dont get in a big hurry if you get a complete gasket set then you can go through the cooling system and clean it good also hone the cylinders and put new rings in. the fun part is putting the crank and pistons in at the same time you need special ring compressors to do the job correct. The more the pistons the harder it is to assemble. GL
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the numbers were 60psi and 110psi. I havent ran sea foam through it yet. Im going to see if that helps first by cleaning the all the cruds out and recheck the pressure. By the way thanks for all the help. Sounds like fun taking apart the motor. Maybe ill just try it and see how it goes.
 
There are several rectangular inspection covers on both sides of the block , remove all of them.---Remove them to inspect pistons and rings.-------Costs nothing to do that.------------ The reed block is not internal ( fit around the crankshaft ) on this engine.----simply remove the carburetor and then the reed block.-------Once you see what shape reeds and the the rubber gasket that seperates the crankcases is in you can decide what to do next.
 
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racerone said:
There are several rectangular inspection covers on both sides of the block , remove all of them.---Remove them to inspect pistons and rings.-------Costs nothing to do that.------------ The reed block is not internal ( fit around the crankshaft ) on this engine.----simply remove the carburetor and then the reed block.-------Once you see what shape reeds and the the rubber gasket that seperates the crankcases is in you can decide what to do next.
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how do you know if the reed block are still good and in need of replacement and can i just replace the rings and not hone the bore.


thanks for all the help guys...keep it comming, all inputs are welcome. I know theres alot of first timers just like me out there who dont know squat bout outboard motor and fore sure i hope this forum will help the next person.
 
kimcrwbr1 said:
http://www.marineengine.com/parts/m...a/crankshaft-and-center-main-bearing-assembly Sorry I was thinking yours was like the early 20hp with the reeds in the center main bearing.
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*thanks for sharing the link. For sure if I decide to go through with this, I will definitely hone my cylinders now. Guess its not a good idea to take short cuts then.
I did what racerone said and took a peek through the rectangular* holes and my piston looks as shinning as it could be. The piston rings looks good and shinning also, it doesn't seem to have any carbon build so how can they be sticking? Im only viewing it on one side only so Im guessing it looks okay for now. No scratches nor scores that I know of. I also took my carb out and peek through the holes to see the reeds. I didn't see any cracks, damage any weak signs of failing. Is there any specific flaw that im suppose to see if my reeds or bad. I didn't want to take out my reeds because i dont have a gasket yet or can i just reuse the gasket for now.
 
kimcrwbr1 said:
Take a screwdriver and carefully push on the rings they should be springy if they dont move fairly easy you likely have a broken ring or scoring you cant see. Normally the scoring will be on the exhaust side the worst. You can allways get some gasket material and make your own, I use a ball peen hammer and lightly tap around the edges to mark it and use a small socket to punch the holes. My book shows the reed stop opening is .007 in and with a hyphen it states the manufacturer recommends the reeds stand open but no more and .007 inch that could be why it failed your smoke test. If you cant get the compression up on that cylinder you gonna want to dig further just be careful pulling the crankshaft needle bearings will fall out from the center main you want to keep them together. Get a complete gasket kit if you determine it can be made servicable. You wont know for sure until you take it fully apart. I would hold off on buying any more parts until you know how far you want to go and research available parts.
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yea i aready tried that, the ring did bounce back in and out when i press on it. I also started the motor and let it* run while spraying sea foam inside the carb for a good 30 mintues. I didnt get the chance to use the whole bottle because i couldnt breath in garage" too much smoke in there so i stop it".
Its seems to rev great and have power still when i engage it on the wot but dies out when i set it on the start position. I havent compress test it yet but will do it asap. I did some search and they do have gasket and piston rings for my motor still. I just gotta figure out if i wanna replace the reeds first or the rings. Some says reeds dont give you a low compression and some says it does, what do u think? Heres a quick link for a fast reed test, do u think i should take it out and blow on it like these guys did* or not...* http://www.youtube.com/watch?v=TiQFIrVME6o
I dont wanna ruin a my reed if its still good. I also blew smoke infront of the carb while pulling on the starter rope and it seems to be sucking the smoke in great, no back draft from the carb. So Im looking around 150 for parts with rings, gasket sets, boring the hole if needed. Ill do some more research on this and see if i* wanna go through with this...thanks
 
That motor has chrome cylinder bores and does not need boring UNLESS the chrome is ripped up. You'll have to tear into it to find out. (Below is a photo of what the guts looks like.)

The good news is that the earlier, Merc 200 (20 hp) uses similar (and MUCH cheaper) rings--I've used them on mine. Assuming the bores are okay, all you have to do is LIGHTLY hone them with a fine hone, clean the block thoroughly, and put it back together.

Mine went from blah compression to a respectable 120 pounds when I did this.

Jeff
 

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When compression is occurring in the cylinder the reed valves are open , so they do not really have an effect on cylinder compression.------------This is a common missunderstood concept !
 
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