Motor only runs good with cowling off :-(

[scottcab]

Hello all,
I figured I would start a new post for my problem to maybe get some fresh ideas.

I have a 1985 OMC 1.6L SeaDrive Powerhead on a 115 Johnson mid and lower. Currently, My motor runs really bad with the engine cowling on. It spits and sputters and has a great loss of power. Sometimes it won't even plane off and when it does it has between 3 and 4k rpm. When I take the cowling off it is like I unleash a completely differant motor. When pressed straight to full throttle, for about the first 3 seconds after running it with the hood off it acts as if the carbs are flooded. Then, it takes off and runs like a top. With the hood off it will do 5700rpm and 44mph at WoT, but it stills seems a bit unsteady at just above idle up to 3/4 throttle. I did take off and clean the carbs. The change from running nice with the housing off to running crappy with it on is almost instantly. Orignially the latch to the cowling in the back left was scrapping the spark plug boot and I believe shorting it out. When I first figured this out, the motor ran great with the other two latches clasped and the back left off. But, after only half of a fishing trip, the leave the latch off trick also no longer worked. I also notice that excess fuel is in the bottom of the motor housing and I have a decent amount of unburned fuel draining from the motor housing at the bottom and also at the prop.

I searched the forums and found potential causes as air flow into the cowling restriction, exhaust leak into housing compartment, and shorting/grounding out of one of the plugs or coils.

What do yall think as a possible cause, and what are the ways to test the probable causes?

I do know that the head has a small exhaust leak from the bottom of the head near the middle (maybe the base gasket). The leak isn't really bad, but do we think this could be the culprit. I was thinking that the exhaust leak wasn't the problem because the change in power seems almost instant when the cover is placed on.

I also don't know it having a omc seadrive powerhead under a 115 johnson hood is a possible cause. The cowling seems like it doesn't have enough clearance. Does anyone know if there are many differences, especially in design/size between the johnson 115 and the 1.6L omc seadrive.

Thanks for your time and help,
Scott

 

[Mas]

Re: Motor only runs good with cowling off :-(

Your base gasket (between powerhead & exhaust housing) is leaking exhaust gases and is choking the motor of fresh air. It's kinda hard to burn gasoline without a good supply of oxygen. By removing the hood, clean air easily enters the carbs instead of exhaust. If you're seeing the leak...it's your problem.

Mas

 

[scottcab]

Re: Motor only runs good with cowling off :-(



Here are some pictures detailing the area where I have an exhaust leak. As previously stated, the leak isn't constant, but it definitely is leaking some. The leak is coming from under the square part in the front and from the gasket area of the gasket that runs horizontally in the gap below.

Is this gasket that is leaking called a base gasket? Does anyone know the part number and exact name for this gasket so that I can track one down. Also, How hard is it to replace that gasket and what all needs to be done? Do I have to pull the whole powerhead off?

I do have the factory service manual for my powerhead, so that should assist me if i need to pull the head.

Thanks
Scott

 

[Mas]

Re: Motor only runs good with cowling off :-(

What you're showing is the exhaust cover...which could be causing your problem too. Obviously, if it's leaking, I'll need to be replaced. Be wary however, the screws on the exhaust cover can easily break...creating many other problems. Is this a salt water motor? Is it also leaking water?

Mas

 

[scottcab]

Re: Motor only runs good with cowling off :-(

Mas, i beleive the exhaust cover is the part up front? The leak is coming from under the flat spot in the middle of the cylinders towards the left side. It looks to me like maybe below the head and above the mid section. I just bought the motor used but i live in south fl so probably been saltwater a long time. There might be a small amount of water leaking, but I cannot tell. There was some thickish black oily substance near the leak. (looked like old car oil)

 

[Mas]

Re: Motor only runs good with cowling off :-(

Check out pages 14 & 15 from this link:

http://dazusfb7pt2uv.cloudfront.net...marine/Sea_Drive/1985 16 SEA DRIVE 984111.pdf

Mas

 

[boobie]

Re: Motor only runs good with cowling off :-(

I just read your orginal post and it could be a hood problem. The seadrives and the outboards used to to use different hoods for water injestion problems.

 

[Haffiman]

Re: Motor only runs good with cowling off :-(

Check your spark plug wires. Sparks jumping to the lower latches from the coils are a common problem on those engines.
Use the original solid core plug leads and be sure they are properly clamped to the heads.

 

[emdsapmgr]

Re: Motor only runs good with cowling off :-(

It's not unusual for a crossflow base gasket to deteriorate/fail. A common problem on older crossflow V4 engines. The base gasket is part number 321727. Not real expensive, but a 3+ hour job to remove/replace the powerhead during the gasket install. The exhaust leak will cause unburned, exhaust to circulate inside the cowling, and right back into the carb throats. That ingestion of exhaust back into the powerhead is probably the best reason to quickly replace that base gasket. On that other airflow issue: A remote possiblility that the engine might have breathing/airflow issues if you mix various years engine cowling/parts. For many early years, the crossflows sucked air into the cowling from a large vent just under the bottom carb. (Some air does enter through the handhold vent in the upper cowling.) Around 1990 OMC eliminated that lower cowling vent. For those later years, they installed large side vents on the upper cowling in addition to the vent around the upper cowling handhold. So-it is possible to create a potentially bad situation by combining an older (single handhold vented cowling) with a 1990/newer (non-vented) lower cowling. This unlikely combination of various year's parts might restrict/prevent airflow to the carbs and cause running issues. You did not mention the specific years of parts you are combining, but it's worth double checking. Possible any airflow restriction combined with exhaust gas recirulating into the carbs might contribute to your running issues. You might also unscrew that handlhold cover on the upper cowling just to make sure it will flow air.

 

[Home Cookin']

Re: Motor only runs good with cowling off :-(

Check your spark plug wires. Sparks jumping to the lower latches from the coils are a common problem on those engines.
Use the original solid core plug leads and be sure they are properly clamped to the heads.

I was thining the same thinig; that the cowl may be pressing on a stray wire causing a short. But the exhaust leek sounds more likely

 

[scottcab]

Re: Motor only runs good with cowling off :-(

Thanks for the replies.
I intend on changing the base gasket because I know it is leaking at least on some level. I took a look at the cover of the service manual. The 1985 1.6l OMC Seadrive had two vents on the sides of the cowl. I do not know the year of the cowling that is being used, just that it is a 115 johnson and that it DOESN'T have any vents. Do I need to do something to allow the motor to get more air? Does anyone have any suggestions on vents to add or a cowl or something.
Thanks again
Scott

 

[emdsapmgr]

Re: Motor only runs good with cowling off :-(

A couple of suggestions. You could use the original seadrive cowl, if you still have it. The 1990 and newer OMC cowlings use two side cowling vents. Port side vent: 432828 Starboard side vent: supercedes 398445 They are about $24 each and are a special order. Most other side cowling vents on these older engines have been discontined. For the expense of these vents, you might be able to find a complete used cowling with vents cheaper.

 

[scottcab]

Re: Motor only runs good with cowling off :-(

Update: Okay all, I need some input. I pulled the powerhead and replaced the base gasket. The old one was shot as expected.

Unfortunately, When I got the head off, the flat portion of the head nearest to the back, between the head bolts and the end of the head seems pretty beat up. Instead of being a flat metal surface, the metal seems angled up and has several dings in it. Thinking wishfully, I installed a new base gasket after putting on a layer of OMC Gasket Sealant. I allowed the head to sit for about 4 hours by the time I reinstalled it and took a break. I then fired her up and felt instantly nauseous. Not only does my exhaust leak seem to have gotten worse in the back from around the base gasket, but now water is leaking from the same area as the exhaust. The head seemed to fit nice and tight. Also, I started the motor in a large bucket of water. (clear water) That is until the motor fired up. I am not sure where it came from (maybe built up in the exhaust passageways). But, The bucket of water became instantly black. As if I dumped a quart of oil into it.

Should this have me concerned? I am hoping that the black death is a result of the motor running rich and `misfiring for a while prior to correcting several problems today (proper sparkplug wires, coil connectors and boots, and base gasket,along with correcting a problem with the latch scrapping the spark plug boot)

My questions: The black cloud, Is it something to be concerned with? If so, what is it and how do I correct it.

The head problem: Even with a new base gasket, the exhaust and water are leaking from the back of the head below the exhaust housing. What can be done here? Someone had suggested to me to pull the head back off and use marinetex to build up the head and then somehow file or sand it back to flat so the gasket will seal. Does anyone have a good idea or how does the above idea sound and has anyone had luck with this plan?

Thanks
Scott

 

[toddschubert]

Re: Motor only runs good with cowling off :-(

How does it run w cowling on now? did wire work fix that? I have had same issue with wires shorting to cowling latches.
Oil in exhaust was probably just built up in exhaust housing.

 

[Mas]

Re: Motor only runs good with cowling off :-(

Sorry to hear about the difficult fix!

How 'bout some more pics?? I've never known any sealer to take the place of metal. You might have to have some machining done??

Mas

 

[scottcab]

Re: Motor only runs good with cowling off :-(

Sorry Mas, no more pics for now. When I pull the head again I will take pics.
Todd, a combination of the new wires plus coil boots and careful placement of wires and latches I believe have fixed the missing problem.

I did a little more research on the marinetex. Their website says "Marine-Tex, the legendary high-strength repair compound designed for filling, bonding and rebuilding metal. Marine-Tex can be sanded or ground to shape, tapped and drilled, and finished with most common paints and coatings."

This sounds like it might be the affordable DIY fix for the edge of the head. Has anyone used this stuff for a similar repair? How well does it adhere and apply?

Thanks
Scott

 

[toddschubert]

Re: Motor only runs good with cowling off :-(

sounds like it might work as the ph is just sitting on it rather than say a lateral or hanging load. But for a DIY purpose. I doubt yould find a tech doing it and warranty it !!!
Also are you sure its not leaking from exhaust housing cover? Flat plate between heads?

 

[emdsapmgr]

Re: Motor only runs good with cowling off :-(

The black, oily substance coming out the bottom end of the engine is usually/typcially normal on a crossflow. If your engine is not running on all 4 cyls, the oil/fuel going out the exhaust is increased. The unburned combustion residue coats the inside of the midsection over time and it will come out the bottom end of th engine. I do see that you have exhaust/oil leaking from the seam between the lower unit and the bottom of the midsection. That is perhaps from a missing or damaged lower exhaust gearcase seal. When reassembling the lower unit onto the midsection, an odd shaped rubber grommet needs to be put in the exhaust groove of the lower unit. It's not unusual for the original seal/grommet to swell with age. This presents problems when trying to reassemble the midsection-that grommet can get out of position during reassembly, causing the exhaust leakage you have in your picture.