3.0 L OMC running rough

[mr snowman]

Hi guys, I am new at this whole boat thing so bare with me. I bought a 1989 Forester 160 Sport that has a 3.0L OMC (4 cylinder) in it. I was told it is a chevy block. The first year I had it there were no issues. The second season I noticed a small water leak around the vacuum tube connection to the manifold (I think that is what it is) that goes from the carb to the manifold. The connection is right near where the gasket is. It still ran ok, but once in a while the motor would bog down and back fire upon initial WOT. I would back the throttle off and give it WOT and there would be no issues. In addition, while cruising around the lake at slow speeds the motor would rev up and down slightly. The dealer said he could look at it but suggested he could take care of it when I pulled it out of the water. Other than that, there were no issues. So the dealer looked at it and "found nothing wrong"
Last season was a little different, The initial launch/ride I noticed the leak again and it was running real rough. So I brought it back to the dealer and they replaced the exhaust manifild gasket. After launching the boat again, the leak was still there and I checked the oil, sure enough there was water in the oil. Mind you I always check the oil and there has never been any water in the oil. I bought it back again and they took the head off and sent it out to check of cracks, also the compresion was good. No cracks were found, but they did find some slight warping so the heads were machined, They put on all new gaskets along with the machined head and guess what? The vacuum line area still leaked , but there was no water in the oil. The motor still has the issue of reving up and down slightly and still boggs/backfires once in a while when I give it WOT.

Can it be as simple as the vacuum leak that is creating the motor performance issues? Can I put some JB Weld on there and call it good? Maybe buy a new manifold?

Or could the carb be dirty/worn and needs to be replaced and there is no link to this vacuum leak?

I look some numbers off the motor if it will help: IM07121RQ N2356

I also took some pictures of the "leak area" if it will help I can email them out.
Thanks for your help

 

[Reel Poor]

Re: 3.0 L OMC running rough

Can you post the pics on the board?

 

[mr snowman]

Re: 3.0 L OMC running rough

I wish I could, I do not have a place to host my pictures.

 

[whywhyzed]

Re: 3.0 L OMC running rough

I think that tube is just a heat stove for the choke - It's not vacuum related if it's the tube I'm thinking of. If water's coming out of that area, the exhaust manifold is cracked and needs to be replaced, not repaired. You could be on your way to a hydrolock and damaged engine.

 

[mr snowman]

Re: 3.0 L OMC running rough

Hopefully this works.

http://aycu25.webshots.com/image/10424/2004162504367466243_rs.jpg

 

[mr snowman]

Re: 3.0 L OMC running rough

I see the link worked. The leak is coming for the area where the rust is to the left of the carb.

 

[Don S]

Re: 3.0 L OMC running rough

That tube is not vacuum, it's hot air that heats the choke coil.
You can get a new tube and cover for that tube, but I doubt that is your running problem.
When was the last time your engine had a full tuneup. Points, plugs, cap, rotor, dwell set, timing set and advance timing check. and carb adjustment. Along with fuel filter check and replace.
Have you done a compression test, how about a vacuum test?

 

[mr snowman]

Re: 3.0 L OMC running rough

The compresion check was fine, but I did not do a vacuum check. Is that something I can do?

I am not really sure when there was a full tune up. I know the dealer runs it and checks everything out when he winterizes it and preps it in the spring.

I can do the plugs, points, cap and rotor myself and I think I can find someone who has a timing gun. Does anyone know what the dwell set, timming set, point gap, and advanced timing should be set to? The fuel filter gets replaced every year.

So if that is a hot air tube for the choke, should there be water coming out of it? Should I start looking to buy a manifold, tube and cover?

 

[cobra 3.0]

Re: 3.0 L OMC running rough

I have the same OMC engine but an `86 also in a 16 ft boat. I had the manifold sanded on a flat sander at an engine shop because this engine has a tendancy to corrode right in the middle between piston 2 and 3. So even if a new gasket was installed, it will not fill the void.

It used to run rough until the engine warmed up a bit and finally quit when the head gasket also blew right in the middle. I had the head replanned too.)

 

[Don S]

Re: 3.0 L OMC running rough

The compresion check was fine, but I did not do a vacuum check. Is that something I can do?

No one here can answer if you can do it or not, we don't know you or your mechanical abilities.
SInce you have a dealer do the winterization and "Looking" at it in the spring, I have to assume you know nothing about engines and drives.
Here is a post I just posted on another thread, perhaps you should do the same.

Why don't you get a service manual so you at least know what things are called when you ask questions.
Not everything can be done on the internet. Sometimes you have to read, study, and understand how things work so you can work on them. Otherwise you won't even know if you are doing something right or wrong when you do work on it.

 

[mr snowman]

Re: 3.0 L OMC running rough

Point well taken, I have already looked into getting a service manual. I am pretty mechanically inclinded and work on my cars. I am not all that fimilar with boats and was seeing if anyone had the same problem. Looks like I will be giving her a full tune up, taking the manifold off for an evaluation, and replacing the hot ait tube foir the choke.

But, should there be water coming out of there? Should there be water in that tube? In the manifold?

 

[Boatist]

Re: 3.0 L OMC running rough

No water should come out. The tube just run down thru the exhaust gas and get hot to open the choke. Some vacuume sucks air from the choke area and hot air should come in the the tube to open the choke. It the same as most Chev from that time.

 

[cobra 3.0]

Re: 3.0 L OMC running rough

The manifold contains the water that comes from your engine and sends it out of your exhaust. There are ports for water and for hot exhaust on the way through the manifold. There should be no mixing of the two at the gasket joint between the head and manifold.

I think your head could have the same problem or is on its way to developing it anyways. As I mentionned, for the year of your engine, this is a common problem area which develops over time and from use. To check it will only cost you the gasket (about $40.00 at an OMC dealer. You can also use the Merc head gasket as it is exactly the same...but check it by bringing in your old one.)

Check for straightness of the head with a straight edge and have it planed too if it is out of wack. Check the middle for signs of head gasket deterioration.

You can also check your valve seats by pouring gas onto the valve chambers and see if they leak. If they do a valve job is in order.

As metionned above, do get a manual and decide if you want to do it yourself.

 

[Boatin Bob]

Re: 3.0 L OMC running rough

When looking for a manual do yourself a favor and try and get an original OMC factory manual such as this one in the link, it's superior to the aftermarket ones, will pay for itself with the first repair. Check your engine model # to see if the last 3 characters are MED or MEF to verify you have a 1989 engine package.

1989 OMC Cobra Manual

 

[mr snowman]

Re: 3.0 L OMC running rough

So if there is water coming out of the tube conection then there must be an issue with the tube,the manifold or the connection. I will definetly look into it and give her a full tune up. I would like to believe the head and head gasket are fine since my dealer replaced them last may during their evaluation, although they also told me the leak was "fixed".

Is there a serial number on the block? The valve cover was repainted and I think they covered up the numbers unintentially. They did this when the short black was replaced three years ago due to improper winterization (previous owner).

 

[Boatin Bob]

Re: 3.0 L OMC running rough

That's too bad about the paint but on the 3.0 the model/serial plate was on the side of the rocker cover, unless it's still there but just covered up?