No Idle

[Philumup]

First time posting on this site. I have an 87 Force 125hp. Was on vacation a few weeks ago and the motor ran good until Thursday. Then it would start, but you had to have the throttle all the way forward in nuetral to keep the motor running. If I backed off the throttle to half way, it would die. Once I got home, I did a compression test: cylinder 1-4 are 100, 30, 115, 120. I pulled the head off and found that the cylinder wall in cylinder 2 is scored. Pistons are ok. I have spark on all 4 cylinders. Bought rebuild kits for both carbs, rebuilt them although they appeared to be ok while rebuilding. Fuel mixture screw is at 1 turn out. Reed valves look OK. Stator measures good. Fuel pump diaphram looks good. New spark plugs. Timing is good. I read numerous threads on this site and there is a lot of great information, however, everything I have tried so far has not worked. I know that the low compression on cylinder 2 is an issue, but for the motor to all of sudden act up makes me think that there is more to this issue than just a bad cylinder. Hopefully someone can help me out.

Thanks, Phil

 

[DukeDelago]

Re: No Idle

Welcome Phil. I'm certainly no expert, but I just had to do a rebuild on my 1990 120 for about the same reason and your compression readings certainly are representative of the performance you are getting from your motor. even the three cylinders in triple digits are not within spec, you should have no more than 10% difference between any two, and you have double that one one. Also, if I remember correctly the correct operating range is 125-145 psi which means not even one is operating correctly. This easily could have happened suddenly if your #2 ring(s) snapped, as they did in mine. You are lucky in the fact that there is no visible piston damage as that can save you some money, but any way you cut it you are in for a rebuild. You will need to do a tear down to see what you are in for. Can you post some pics of #2 cylinder so we can see how bad the scoring is?

 

[Philumup]

Re: No Idle

Before this happened to the motor, I was capable of going about 45mph. Had plenty of power. My tach does not work, so I do not know what I was at for that. I will get to the motor tomorrow hopefully and I can take some pictures of the cylinder. The scoring was fairly sufficient. I work with a guy that works on cars and he said it would need to be bored out when I had him look at it.

Thanks, Phil

 

[DukeDelago]

Re: No Idle

If it's the scoring that is causing compression loss that significant (and not the rings) it will definitely need to be bored oversized. .030 over pistons are available online and not terribly expensive (3.375 is your standard size, correct?). Remove the powerhead and do your tear down first. Once you have the block separated and crank/rods/pistons removed (remember to keep each cylinders parts labeled and seperate from the others) you can inspect everything and order parts. Depending on what #2 looks like, you may try honing it and it might be ok. Otherwise take the block to a machine shop and have them bore it, not terribly expensive. If the pistons and cylinders are fine in the other 3 cylinders I would still replace the rings and hone the walls, it should help with compression on these as well and save you the trouble of a second rebuild next season!

 

[jerryjerry05]

Re: No Idle

Low comp on 1 cylinder will cause all kinds of trouble.No idle,hard starting, poor performance etc.
Take it apart before any more damage is done.Start at 10 over that way you won't need to re-jet.
Usually the scored walls will affect the pistons too.The sides will probably be scored and have melted aluminum there.
Fill out the profile.You might be close to someone who can help.J

 

[QMAZIGGY]

Re: No Idle

even forgetting the dead hole, this engine has problems. The split from 100 to 120 PSI is beyond what most consider acceptable, and in the light of the dead #2 hole, a full teardown and inspection is mandatory.

 

[hoofbite]

Re: No Idle

I had the same problem last week however mine was an easy fix the linkage actually popped off so in neutral the thing would rev right up. Buy in gear only idle speed I was ready to pull the plug and call my insurance company!! But a second look I noticed the linkage attached to the advance about 3" or 4" inches long popped off?? Is just a friction fit and popped back on!! Sure enough ran like a champ. Now I'm sure your issues might be a little more serious. But hey something simply over looked can really make you breath a sigh of relief However your #2 compression is a major issue if it is the linkage at the very least you might be able to use the boat until such time you can make the repairs. My 2 cents.

 

[Philumup]

Re: No Idle

I have attached some pics of the scored cylinder walls. Two pics are of cyinder 2 which is bad, one pic is cylinder 3 which feels very smooth and one pic is the head of cylinder two. I will look into having the motor rebuilt. Thanks for the help.

 

[Philumup]

Re: No Idle

Removed the motor today. Going to start the rebuilding process. Will update when I start the motor back up after completion.

Phil