35 TE STB Side Engine Mount Galvanic Corrosion Issue

[dmorlo52]

Per the subject, I have noticed an accumulation of white sticky (gel like) material on my aft and forward STB engine mounts. I know that galvanic attack needs stray current, moisture (salinity is worse) and a sacrificial anode. In this case the anode is the T6061 T65 aluminum motor mounts as the mounting bolts are all stainless steel. There is evidence of corrosion wasting around the bolt holes and the top of the aft mount and the bottom and top of the forward mount. I also see a crack at the toe of the fillet weld on the aft side of the forward mount that extends to the nearest bolt hole. It appears then that water is getting to this stringer. Does anyone think it is from the keel up into the stringer? There is no evidence of leakage outside of the stringer or through the drainage opening from the angles floor to the bilge. Feeling in these drain area does not show any moisture. This was like this when I bought the boat last year but no one new what this substance was or had any ideas. I thought maybe water got in at some point and it was sealed and the retained moisture is causing this. Any ideas? If there is no current water intrusion to this stringer and it is old moisture would a separate ground from each mount to proper ground bar stop the activity?

I hope the pictures make it and it helps analysis.
David
2005 35TE
WINEDOWN

[rcwhite]

Seems unlikely it would be coming up from the keel. Have you checked to see if your dorade boxes are intact?

[dmorlo52]

What is dorade box and where are they? The rest of the engine compartment is corrosion free. I do have blowers that work fine and offer some air move when not in use.

David

[rcwhite]

The dorade box is located behind (inside) the vents on the side of the hull. They help to limit water and spray getting drawn into the engine room. They can deteriorate and may be worth inspecting.

[dmorlo52]

Thanks, I will take a look.

David

[Halcyon]

there are two types of Vetus dorade boxes and the ones supplied on my 2004 boat are supriseingly cheesy. Vetus' web site offers the upgrade, an easy fix.

[dmorlo52]

Thanks for the info and pictures. My dorade boxes are hidden behind the water tanks on both side of boat. I am not getting any water in from the vents but the STBD stringer seems to be wet and there is dampness in the drain holes to the bilge.

David

[RobS]

Have you used a moisture meter or IR camera to see where the wetness in the stringer starts and stops ? Does it go all the way back to the transom where a swim platform bolt or trim tab fastener could be the culprit? Does it ever dry out now that she's sitting in the water? If not it's unlikely it's from rain or especially spray.

[dmorlo52]

ROB, An infra red scan last year on the hard showed moisture from the transom to about 3/4 the length of the stringer. It appeared to be entering at the STBD trim tab. Trim tab was removed inspected and resealed including all screw holes. If this was the fix how long or would the stringer ever dry out? What is the stringer made of? There is no issue of glavanic attack on the port engine mounts. If you hammer tap both they sound the same. No clear path of water from stringer drain hole to bilge. I'm stumped.

Another issue I am having is lost of engine rpm. Over the winter had new exhaust riser designed and installed. Top of exhaust pipe is now just under salon floor with new mixer and all is 316L SS. Also had flo-scan installed so maybe one or both is causing me to only get 2800 at WOT. New fuel filters in spring of this year and all connections are tight so no vacuum leaks. Engine sounds good and turbine winds up ok or so it seams. Did a turbo wash also under load with no change in rpm. Any ideas?

[RobS]

Not 100% sure on the stringer construction Albin used, someone else may chime in with that, could be wood or foam core or could be no coring at all, just an open channel glassed to the hull. It's the shape of the stringer and not whats inside of it that provides the strength. Regardless, the stringer would never dry out being encapsulated in gelcoat.

Are there any limber holes in the area that may be unsealed or any holes added "after-production" and left unsealed?

Did it ever get the proper WOT rpm's with the new riser? If not, could be a back pressure issue in the new exhaust design.

[dmorlo52]

The limber hole forward of the front motor mount showed some wet wood (like saw dust) when I checked it out. There is also some gelcoat that is raised that would trap water instead of letting it into the bilge. The aft limber hole was ok. When you feel with your fingers the stringer above the limber hol it feels smooth and solid. These are massive stringers and appear to be solid.

Since the new riser and flo-scan were put in at the same time over the winter, either one could have an affect on rpm. The waste gate is also frozen in the wide open position so that should not have any bearing on the turbo rpm. Do turbos just gradually slow down? If so can they be rebuilt or should you buy new?

David

[dmorlo52]

Rob here are the riser pictures and one of the new awlgrip paint and transom decal. (and the first mate)

David

[rcwhite]

If you have a waste gate that is stuck fully open, I would expect trouble developing boost and reduced top end.

[dmorlo52]

RC

Makes sense to me. I guess with proper waste gate function boost would develop quicker while gate is only partially open vs wide open all the time. Should I replace waste gate and hope that is the issue with reduced rpm of 500+. Plan on putting a boost gage on temporarily (and then forever). Also vacuum gage on fuel line to check draw. I am sure waste get is much cheaper than the turbocharger at $3100.

David



David

[rcwhite]

Yanmar 6LY with RHC7W turbo?

The wastegate is a component in the turbo that is basically a bypass to control or limit
the boost pressure. Normally it would be closed until you build full (or close to full) boost
pressure so if it is stuck open, I wouldn't be suprised if the engine wouldn't spin up under load.
It would be unlikely that it would build enough boost to reach full RPM.

If is is just stuck from carbon or sitting too long, it may be possible to free it up.
Otherwise is the actuator or linkage bad?

Did it get wet, hence the new risers? If so and assuming no other damage, it may still be
possible to free it up but...

Chris