Pontoon Boat & Deck Boat Forum

I decided to bite the bullet and commit myself to getting my Tri-toon houseboat back in the water. My Suzuki DF 90 has the factory installed steel exhaust port plug that will corrode and eventually cause motor failure. I've seen pictures of Youtube failures where someone tried to force them out and ending up destroying the housing. I took an outboard maintenance/repair course years ago and the instructor stressed to NEVER force any fastening devices on an outboard...best advice of the whole course! The first thing I did was soak the frozen plug with Blaster for several days. I tried breaking it loose with a short 3/8 breaker bar, it should have given me enough leverage to break the plug loose without breaking the housing...it didn't. So I tried applying a little-localized heat with a map torch, the expansion and contraction of metal will sometimes aid in loosening a corroded fastener...it didn't. Ok, time to bring out the big guns, a drill with graduated bits. I started with a 3/16 and worked up to a 5/8 keeping the bit centered. This left a thin ring in the housing which I remove by tapping round and downward with a small chisel. The plug has an 18mm x 1.5 thread and fortunately so does my spark plug thread chaser which I used to clean out the threads. Hope this helps anyone else attempting this fix to have patience and do it right and not destroy their housing. Here's a couple of pics with the Gold Plug/aluminum made in the USA.

How would you know it is getting corroded? How does it cause engine failure?
TIA

[quote="bansil"]How would you know it is getting corroded? How does it cause engine failure?
TIA[/quote]

08’ and older DF90 DF115 and DF140 used in salt water mostly have the issue. I’ve seen some high hour fresh water motors have the plug stuck but haven’t seen one rot through completely. The plug was stuck pretty good on mine but had no noticeable corrosion once it was out, either did my buddies DF115.

I just happened to see it mentioned, maybe on this forum, then I did a search on the internet. Suzuki used a steel plug where they should have used an aluminum one and the difference in metals causes corrosion. Eventually, it will corrode through and let water seep in.You can see the corrosion around the steel plug by doing a visual inspection. Fortunately, mine was mild but still enough that I couldn't screw it out even after using Blaster and locally applied heat. By drilling it out in steps I got it down to a thin ring (without buggering the threads) and then tapped the ring inward a pulled it out with pliers. Then chased the threads with 18mm x 1.5 chaser (Same as sparkplug).

hopefully will have nice weather this weekend to look at mine

So tired of below freezing and snow/sleet