Is this true about ?

[fuzzymaster]

I am looking at a 2006 115 four stroke mercury, and got this info from anothet site. Want to verify info

And that is what causes the problems with this generation of 4 cylinder 4 stroke Mercs (40-115hp) - there is a grommet in the waterways between the leg and the power head. A mismatch of Merc to Yamaha metals causes corrosion which close up the rubber grommet which closes off the water flow. A tiny part but the powerhead has to be removed to rectify it. According to my independent mechanic, it's not a case of 'if' this will happen, just 'when' - usually about every 5-6 years, so check this has been done and be prepared to do it again - because it's caused by the mismatch of metals, no amount of flushing will prevent it, although I have heard of people doing things like painting the internals etc to slow it down - but I have no idea if this works or not.

Thanks for any other info on this motor

 

[Texasmark]

Re: Is this true about ?

I don't know if Yammie has anything to do with that HP engine. I know they built a lot of the lower hp engines and may have supplied parts for others. Tohatsu built them too. I doubt any of them use anything but aluminum in their castings. Doesn't make sense and there isn't much if any electrolysis between metals made of the same material. The Zinc sacrificial elements you see on engines are to protect the alum from eddy currents with other things, like the boat hull.

I'd assume that the 4 stroke is a cast iron lined cylinder with an aluminum block mated to an aluminum mid section, mated to an aluminum lower unit. I do know that Mercury spent a lot of time over the years developing corrosion resistant metals and coatings to help their engines stand up to the elements, especially salt water. They had a testing ground named Lake X in Florida where they punished their engines to find the soft spots. Plus they were into racing big time where a lot of lessons were learned.

Dissimilar metals can develop an eddy current and cause corrosion but most of these engines are aluminum with some other substances to help in the anti-corrosion process. Additionally, the engines are painted with a Zinc etched primer and Phantom Black Lacquer top coat(s). So you really don't have metal to metal contact I wouldn't think.

Main point for corrosion would be between the SS hardware and the alum castings as I see it.

If I were serious about this engine I'd get some more inputs from reliable sources. Also, if this were a problem was it identified by Merc and when.

 

[bilge rat jim]

Re: Is this true about ?

As stated by Mark, Yamaha had nothing to do with that year/model of outboard. The "grommet" (seal) you mention seals the water pipe from the pump to the block, and the only metal it contacts is the aluminium block and the copper alloy water pipe. The only time you should have a problem is if the water pipe is incorrectly installed, pushing the seal into the block, or if the block has been seriously overheated, causing the seal to fail. I can find no service bulletin from Merc on this part, but if you can post the serial number, I'll have a further look.

 

[out 2 launch]

Re: Is this true about ?

Dissimilar metals can develop an eddy current and cause corrosion

I think you have eddy currents and galvanic corrosion confused. Eddy currents are a result of electromagnetic induction, galvanic corrosion is a result of dissimilar metals exposed to an electrolyte.

 

[Texasmark]

Re: Is this true about ?

I think you have eddy currents and galvanic corrosion confused. Eddy currents are a result of electromagnetic induction, galvanic corrosion is a result of dissimilar metals exposed to an electrolyte.

You are correct sir. Apologize for the sloppy usage of terms. Course I have been retired since '04 and have forgotten more than I learned.

Mark