Need help with my OMC 3.0

Hi All,

Specs: 1985 OMC 3 liter (140 hp) with a Stringer 400 out-drive on a 17ft Glasscraft.

Problem: Melted exhaust hoses (boots) and Exhaust Seal (flapper)

Took the boat out for the first time after winter and after about 5-10 minutes I noticed we were taking on water in the bilge. Turned on the bilge pump on and headed for shore, soon after the engine compartment stated pouring out black smoke from the melting rubber presumably.

I was monitoring the temperature gauge closely prior to overheating and all was normal, but once the smoke stated billowing out the temp gauge shot up. I suspected that the t-stat had been stuck, which caused the riser to melt the rubber components and then released which allowed the water to flow again and in turn flooded the bilge.

As I now understand, there should be water flow regardless of whether the t-stat is opening so my first question is:

What conditions would have caused the riser to heat up so much that it melted the rubber hoses and and exhaust seal? I suspect the impeller but then how was there enough water flow to flood the bilge?

Secondly, I'm looking for some advice on the easiest way to access the area where the exhaust flapper should be, to replace it. I already have the out-drive off but it looks like I will need to remove the intermediate housing, I just haven't been able to find many schematics or help on the exhaust seals for the pre 86 3 liter OMC and stringer drive.

I do have an original factory repair manual, but it shows nothing on the exhaust seal.

And lastly, are any other areas that I should check out as potential causes or that may now have potential problems as a result of the overheating.

Thanks in advance,

Scott

Sorry about the thread hijack asperk, but it had the only schematic i have found that actually showed the exhaust seal(flapper)

Pics below

Re: Need help with my OMC 3.0

CNC, we ask that you start your own thread for your questions instead of tagging them on to someone else's. I went ahead and moved your post to start your own thread. You may want to add more detail to it now ...

Re: Need help with my OMC 3.0

Water should always be going to the exhaust. Whether the t-stat is open or not. That isn't what caused your issue.

The flappers usually end up in the lower part of the y-pipe and drive, so yeah pull it. Do all the other recommended maintenance tasks while you have it off. An FSM will help.

Re: Need help with my OMC 3.0

Thanks for the info Levinz, I did find the burnt flapper in the exhaust port of the intermediate housing and have attached a pic above along with the new one.

Re: Need help with my OMC 3.0

Well, after some tedious wrench turning to get the intermediate housing off, I was able to get at the exhaust seal (flapper) mounted inside the bell housing.

The root cause of my overheating appears to be a broken impeller housing, looks like there was some water trapped in there over winter which split the housing.

Now, just need to get some gaskets and a new housing and do all the recommended pm while the outdrive is off.

Pics attached for reference.

Re: Need help with my OMC 3.0

storing the drive over the winter in the full lowered position or tarping it will prevent the impeller housings from getting broken like that. A common issue on 1978-1985 stringer drives and I have even seen the upper gearcase cracked as a result of rain/snow freezing in the water pump area.