K&B 3.5 sleeve & piston ??s

[DaveG]

Ok, I got this 3.5 outboard off e-bay. It's in pretty good physical shape and runs like a bat out of .... UNTILL it gets hot. I get about a 1/4 tank of fuel through it then it starts to give me problems. At that point it runs pretty poorly...won't get up to full speed and when I get it tweeked to get close to top speed it won't run at idle at all. When it's doing this it will start to act like it will run then just dies. I can sometimes catch it and feather the throttle to get it to keep running but then it will only run slowly and poorly.
I've replaced the fuel lines and gas tank thinking I might have an air leak. I also cleaned the carb thinking there might be something blocking the fuel flow. I've replace the glo plug several times. Nothing has changed how it runs.
So, now I'm thinking piston and sleeve. I've read that these symptoms can be caused by a worn piston & sleeve. I pulled the glo plug and rotated the engine by hand and cannot feel any difference as the piston moves up and down. I thought that I should feel the piston travel get tight when the piston gets near the top.
Ok, now the questions.
Will a worn piston & sleeve cause this problem?
Is there a trick or easy way to get the sleeve out of the cycilnder?
I've been to the K&B site and think I know which set to order but is there any way to tell which model engne I have?
Is there a beter, less expensive place to get the replacement parts.
Thanks for any help you can give.
Dave

[Ron Olson]

A worn sleeve can be the problem. Most sleeves are taper bored so they expand once they get heat built up in them. They can feel tight when cold yet looosen up when hot. The engine can be going lean once it's warmed up also so try it a little richer.
There are several ways to remove a sleeve that is tight. One is to heat the case in an oven or stick something soft like a popsicle stick in the exhaust port and rotate the engine to pop the sleeve up. Pliers and screwdrivers shouldn't be used unless you are tossing the old one away.

[piper_chuck]

Before you go to the trouble of changing the piston and sleve, what are you using for a glow plug? I had put my outboard away for a few years and then got it back out to run. Not sure what I was thinking (or perhaps I wasn't thinking) when I put a Fox plug in it. No matter what I did to the mixture, the engine just wouldn't open up. It would run, but the top end was completely lacking. After much frustration, I pulled the plug and put the proper K&B plug in it and the problem went away.

[CFRACR]

I agree with Ron, try running richer!! Outboards like it a little on the rich side. Give that a shot before you tear the engine down.

[DaveG]

I thought I'd post a follow up on the problem I was having with this engine.
It turned out to be a combination of about three different things. First, the K&B glo plug I had turns out to be weak and the OS ones I've been using in my MT's would run but not idle. I put a fox plug (it's all the LHS had) and that problem pretty much cleared up. Next, running richer did seem to help for a short time but the boat would revert to the dying problem after a few runs. It turns out that the hsn was moving on it's own, sometimes richer sometimes leaner. Once I tightened the locking nut down a bit tighter I was able to keep a setting and start to get the boat dialed in.
So, thanks for the suggestions and help.
Dave

[piper_chuck]

I thought I'd post a follow up on the problem I was having with this engine.
It turned out to be a combination of about three different things. First, the K&B glo plug I had turns out to be weak and the OS ones I've been using in my MT's would run but not idle. I put a fox plug (it's all the LHS had) and that problem pretty much cleared up. Next, running richer did seem to help for a short time but the boat would revert to the dying problem after a few runs. It turns out that the hsn was moving on it's own, sometimes richer sometimes leaner. Once I tightened the locking nut down a bit tighter I was able to keep a setting and start to get the boat dialed in.
So, thanks for the suggestions and help.
Dave
Glad to hear you got it fixed. It's fascinating that yours likes Fox plugs and mine hated them. Of course I last had that problem sometime in the mid-80's, so your Fox plugs could be better.

[tj03]

i just pulled mine ( 3.5 tunnel ) out a week ago, and i'm having a hard time getting the power down. when i hit the throttle it jumps good, but then the prop makes an air pocket. i have to let off and go slow then when it gets going pretty good, it flips over sideways. does it need turn fins or trim tabs