ATTN Joe Reeves Problem with 86 OMC 115 hp

" I posted this earlier at FS

" I posted this earlier at FS and I was told Joe was the man about OMC's and to post a reply here to get an answer. So please Joe if ya cna help , I would appreciate it. Thanks


Ok I have about 25 hours on a fresh rebuild and for some reason the engine doesn't want to get up in the rpm's that it is supposed too. But when I take off the cowling on the motor, hang on, the motor reacts totally different when the cowl,ing is off. Anyone ever have this problem with OMC's??? Seems like the motor is choking to get air. Any suggestions would be apprec. "

"Weed..... First, going by mem

"Weed..... First, going by memory, and in checking my books, I can find no record of OMC manufacturing a 115hp in 1986. What is the model number of your engine?

There is an air intake in the lower cowl pan, under the bottom carburetor, and another one at the top rear portion of your hood. It's unlikely you have either of those vents/intakes restricted.

That leaves only one cause left which is that somewhere along the line, an exhaust passageway has access to the powerhead area. With the hood on, the engine is drawing exhaust fumes into the carburetor area. I can only advise you to examine your engine closely to locate the faulty area.

You say you posted this eariler at FS. What is FS?

Joe "

" FS = [url]www.floridasportsm

" FS = www.floridasportsman.com, I was told by a forum memeber at FS that you are the man to talk to about OMC. Ok I have a 1.6l OMC(1986, I assume it's a 115, but might be a 140). there isn't an opening in the front of the cowling, but there are 2 openings in the top rear of the cowling. I checked the inside of the cowling and even removed the plastic bracket inside thinking that it might be causing the restricted airflow. But no avail. The Boat is a 1986 sportcraft with a full transom, the motor is mounted on a bracket on the outside of the hull. I always thought that the motor looked like it sat to far back and down for my boat but it looks like it has always been that way. (SHRUG) Now as for the exhaust"leaking" back into the powerhead, I have no idea. Is there a test I can do to check this situation? The only problem I had when I had the cowling off is that the water tends to wash up on the motor when I get off plane, so the cowling has to stay on motor. So I am to assume, when you mean the exhaust is leaking into the powerhead where the carbs grab the air from, the exhaust air is being reused again, correct? If this is true then I see why the motor was acting like it did. Is this a common problem with OMC's? And any idea what it is going to cost to fix this problem? Thanks you for your insightful comments. "

"Weed.... When you say that yo

"Weed.... When you say that your engine is a 1.6, I automatically assume that you have what is called a "Sea Drive".

Where the exhaust fumes might be coming from, I have no idea. I doubt very seriously if they're coming from outside the engine and being drawn into the air intakes. If that was the case, when underway at anything above idle, those fumes would be left far behind.

I suspect that there is a exhaust leak somewhere in an area where the exhaust is being forced directly into the powerhead area. This would result in the carbs drawing exhaust fumes regardless of the forward motion of the boat.

If this rig at one time operated properly, but has not since the rebuilding, Something has been left undone. If on the other hand, you just purchased this rig, and it has never operated as it should, I'd suggest you have a heart to heart talk with whoever sold it to you.

This is definitely not a common problem. It happens but few and far between. What it will cost to cure the problem is a mystery to me of course. I'd suggest using a portable tank, add a little extra oil, run the engine on a flushette with the hood off, and observe where the exhaust smoke is coming from. I do wish you luck.

Joe"

" Thank you, I will get a chan

" Thank you, I will get a chance on next Tuesday to put those ideas to the test. Yes it is a Sea Drive. Does that make any difference? The motor was rebuild about a year ago and the motor has never ran right. Would the exhaust gasket be lettin the hot gas pass thru the gasket? Is someone gonna have to pull off the powerhead to replace a gasket? I know you can't probaly answer my question without actually seeing motor, but I am very mechanically inclined, and NO I didn't rebuild the motor. I took it to a so called professional who only works on Johnny's, rudes and Sea Drives, guess cause they are all basically the same. Where are you located? You seem to know your SHEET, even without seeing the motor, you were able to diagnos(sp) a possible problem that 3 other marine mechanics couldn't figure out. Will let ya know what I find. And agian THANK YOU VERY MUCH! "

"Weed.... Pulling the powerhea

"Weed.... Pulling the powerhead or not would depend on where the exhaust gases/fumes are coming from. And yes, the Johnson/Evinrude/Sea Drives are just about the same. They have minor differences with the Sea Drive being more so due to the boat attachment arangement. How long ago did that fellow rebuild it? He's obviously made a mistake somewhere. And regardless of the time factor, I would think that he would find and correct the problem, now that you know what it is, at absolutely no charge to protect his mechanical reputation. Keep me informed. I'm located in Central west Florida, near Tampa. Where are you?

Joe"