OMC V-6 cooling modification

[Scoot]

I have a 1996 Johnson 200 Venom on my 22' Blue Wave. It spit an index pin on #4 piston the other day, putting a nice scratch in the cylinder wall. I have read about a cooling modification to remedy the problem but can't find any specific info, other than where to ship the block off to have it done. Does anyone know what this entails? I grew up in an Evinrude dealership, so have plenty of working knowledge regarding OMC products, and have always done my own wrenching on my boats, so skill isn't an issue.

Thanks in advance for any help!

 

[Dhadley]

Re: OMC V-6 cooling modification

By index pin we'll assume you mean a ring locating pin. Probably the top ring. There were some bulletins out on that cooling mod but if you go back with OE pistons it may happen again anyway. I don't believe they ever moved the top locating pin. I believe it's still in line with a finger port. The bottom one isn't.

If you use a Wiseco neither pin is in line with a port.

 

[Scoot]

Re: OMC V-6 cooling modification

According to the factory service manual, dowel pin would be the correct term. Do you know anything about the cooling mods? Could probably do it myself if I knew exactly what needs to be done.

 

[HighTrim]

Re: OMC V-6 cooling modification

I may be off track here,and am unsure about the exact year targeted, but remember reading a service bulletin about installing the water outlet fitting at the top of the exhaust cover. The point in making the modification is to ensure the block gets filled with water by filling through the bottom of the block and venting out the top through the tell tale hose. With a full block, water press should increase. Also about removing the nipple on the cowl.

 

[Dhadley]

Re: OMC V-6 cooling modification

That's part of it. Just like venting the top of the water passage over #1 cylinder helps get rid of air pockets. There are small holes in the water jacket going over to the main chamber that need to be clean and open. I believe they can be enlarged. And there was a bulletin about another water diverter. You'd have to get the specific bulletins and follow the instructions.

Venting the block was something we found so it won't be in a bulletin. Do a search here on block venting, you'll find lots of reading.

 

[Scoot]

Re: OMC V-6 cooling modification

Thanks for the tip. Not having any regulator problems, but will probably check the blow off valve and see if it needs that 1/8" hole drilled. Lost the pin out of the #4 piston, so I don't think it's a venting problem, but it can't hurt. The modification I'm looking for involves swapping out some deflectors along with re-directing the water flow to help cool the port side.

Will definitely use Wiseco pistons in the rebuild.