Expert help needed 75hp Merc!!!

[Skippy the skipper]

Ok, this is a long story but hopefully someone can help me out with this one.
1st off, 1985 75HP Merc will not idle correctly. under 1300 RPM it gives it up and dies. Start off with simple things like spark and compression, spark cks good compression a little different on one cly but within 10% of the others. Check carbs and they are dirty so I clean them out and still cannot get the engine to idle down without stalling. Now I'm looking for air leaks. Look at the upper cap and it looks like someone has been pried off with a screwdriver and doped it up with the red engine block gel. Ok pull the powerhead and split the block to get the upper cap off and it has been tweaked so bad I decide to replace it, block looks ok. Look at the bottom cap and it is loose, only one bolt left and it is halfway out. Measure and shim caps. Since I am in the block, I inspect the pistons and find the one cly that gave a different reading had a broken ring and a tiny scar on the piston wall and piston. Hone the block out and replace the piston. Now I find a reed cage has a chip in it and decide to replace the cages and reeds with the same parts motor I got the cap from. Put it all together and it does idle better but just not right. Dies at about 650/700 on the hose. Hard to start, I have to choke it and advance the timing to start it warm. Anyone have any other ideas? A brief synopsis

1. Cleaned carbs (found problems)
2. Replaced upper and lower caps and seals/o-rings (found problems)
3. Replaced reeds and reed cages (found problems)
4. Resealed case
5. Replaced piston w/bad ring (found problems)
6. Performed link and sync

Any help would be appreciated, Thanks Skippy!!!!

 

[corm]

Re: Expert help needed 75hp Merc!!!

Hi,

One thing that comes to mind is that your reed blocks my not be seated correctly in the block. Did you tap them down to seat them before you bolted down the crankcase cover? A light tap with a light plastic hammer will help square them in the block. Also did all the reeds look like they were sitting flat?
The engine likes rich idle needle settings too 1 1/2 or littlle more turns out. I think mine are 1 3/4 out.

 

[Skippy the skipper]

Re: Expert help needed 75hp Merc!!!

Yeah I did tap the reeds down lightly but I now think it is stll an air leak by the reeds or somewhere on the top 2 cyl. At idle I squirted some powertune in the bottom carb and it bogged the motor down like normal but when I did ther top carb, rpms picked up. I hope it's not a crack or something. Right now I took off the intake transfer port cover but have seen no damage but it had some red sealant on this gasket too. Well I'm headed back out to see if I can find anything else.

 

[Skippy the skipper]

Re: Expert help needed 75hp Merc!!!

well replaced the transfer gasket and still no dice, fuel pump looked great. Must be a leak around the redd plate or something. Anyone else have any ideas?>???