Dealing with the reality of galvanic action on Honda motor

[Yellowstone]

As the old cliche goes, experience is a dear teacher. My lack of understanding of galvanic action on dissimilar metals left me unprepared to handle what I thought was a routine kind of service for a backyard mechanic. Add to that was the use of the wrong tool which resulted in a botched up job. From that experience I have concluded that both a better understanding of galvanic action and some key maintenance practices may have prevented what happened when I attempted to examine the water pump on a Honda 45. Perhaps what I have learned will help other boaters who have a similar experience. I have also concluded that the problem I encountered is probably common to most outboard motors, particularly those used in salt water.

Facts. I gave my adult son a 20' Lund with a new Honda 45 on it in 1996. He used in sparingly (less than 200 hours) until last year when he returned it from the Mississippi gulf coast. I decided to use it this summer and immediately discovered the water from the pee hole was very weak and eventually quit. Reading up on the matter, it appeared the problem could have three (3) causes: plugged up water passages, a bad impeller, or a bad thermostat. Because of its age and area use, I purchased a new thermostat and a complete water pump kit. Yesterday, armed with a Honda repair manual, I decided to replace those parts. Replacing the thermostat was a snap, but removing the four main bolts (hex head 10 x 40 mm) holding the lower gear assembly was a nightmare.

These are SS bolts which thread in from the bottom which makes using penetrating oil difficult. I used the wrong socket - a twelve point, rather than a hex head socket and burred the first bolt head. Using the correct socket after that, I still needed a cheater - three foot long pipe - to have enough leverage to turn the bolts. And they turned with great difficulty every revolution. With a 1.25 pitch, that is a lot of turning. I was worried about breaking off the bolt heads, and on the final bolt, it happened, leaving a broken bolt in the upper housing.

The lower gear assembly was easy to remove then, and an examination of the impeller showed it to be badly warped and frayed. The inside of the upper and lower housing showed virtually no sign of corrosion. But the bolt threads showed the results of galvanic action between the SS bolts and the aluminum alloy.

Talking to a local marine dealer, he stated he wouldn't touch an outboard that had been used in salt water. Questions for the readers. Isn't there some kind of goop that could be used to lessen the effect of galvanic action on bolt threads and the housings? Any suggestions how to remove the stuck bolt stud without ruining the housing? Any advice would be greatly appreciated. John

[ccflyer]

My marine mechanic suggests replacing the water pump every third season since it's cheap way to prevent big head aches.
However, at the end of each season he suggested I take out the bolts holding the lower unit and coat them with the blue marine grease.

[thataway]

The motor should be flushed, and washed after each use in salt water--the use of Salt-A-way will help. There are several anticorrosion/anti siezing compounds which are usuable in SS bolt/aluminum housing applications. I agree with every three years replacement and recoating each season if you just losten the bolts. check "Never seeze" products.

when cruising, at least tip the motor up each night, and then wash it down--when there is fresh water, you can still flush most Hondas thru the flushing port, but that will not fully rinse the impeller and impeller housing. It takes the "dog ears" to do that.

Hondas seem more susceptable to corrosion than some other outboards in salt water.

I like PB blaster or AeroKroil as penetrating oils. Bring the motor as far up as possiable and keep soaking the bolt (I assume that the lower unit is still off)--do this for several days. Then heat the SS Bolt, tap it, and heat again, allow to cool, and hopefully the expansion, contraction cycle will have broken loose the corrosion. (I suspect that Larry or some others may have some better ideas)--Use vise grips on the bolt shank to twist--also you can square off the bolt, and then use an impact wrench if necessary.--I have seen cases where folks have welded a short section of bolt and bolt head to the broken stud in the engine and then allowed use of an impact wrench. (be cautious welding--make sure that there is no electronic module damage--by removing the module.

[Larry H]

John,

As stated above, removing and coating the bolts every couple of years is the best preventative.

In my O/B shop we used 'gasket sealing compound' (a thick brown liquid) to coat the bolts. Gasket sealing compound is available at BRP (Evinrude/Johnson dealers) and auto parts stores. Never seize, or grease could be used also. The idea is to fill up the space between the bolt threads and the housing and seal out the salt water.

Bolts that don't move with a reasonable torque on the wrench should be heated with a propane or MAP gas torch (not acetylene, acetylene is too hot). Heat the area where the bolt threads are in the aluminum housing. Heat until the paint almost smokes. Don't overheat with a MAP gas torch, as you can melt the aluminum.

When the aluminium has expanded enough and released the bolt, it will turn. Work it back and forth and apply heat as needed till its out.

When reinstalling the bolts, use a torque wrench and tighten to the correct torque. Overtightening can break the bolt or strip the threads out of the aluminum.

[Captains Cat]

I feel your pain! As the former owner of a 94 CD22 with two 45's on it, on which I changed the water pumps several times, I didn't experience the galvanic reactions. My boat was kept in Salt Water, but only for the last couple of years. You might check to ensure the ground wire is firm between the mount and whatever is "ground" on the boat. And make sure the zincs are not too far gone.

Good luck getting the bolt out, sounds like Bob Austin has that covered pretty well!

Charlie

[Yellowstone]

Thanks cc flyer, Bob, Larry H & Charlie for your recommendations regarding my dilemma. Hopefully, others reading these posts will do the simple maintenance outlined. I'm going to check on the bolts of my 115 EFI Mercury today. Unfortunately, this story does not have a happy ending. I tried all the ideas, heat, etc., to no avail. The bugger just won't come loose. I also discovered that two of the holes have hairline cracks in the inside of the housing due to the stresses of turning the bolts out. I chased out the threads with a new metric tap, and they will hold new bolts (on order). What to do now? My only strategy is to drill dead center with progressively larger bits until I can rethread the hole to fit perhaps an 8MM SS bolt, or if I'm lucky the original 10 MM hole. What caught my attention is that the threads on the three bolts which turned out were in good shape save about 1/8 inch of the threads at the beginning of the upper housing, and those threads were filled in with metal, like they were welded to the housing. This boat was never in a slip but stored on its trailer. The sacrificial zincs on the motor appear to be in good shape, but the six cleats (zmack) on the aluminum hull were heavily pitted. The current must have been flowing even out of the salt water. We live and learn. Yellowstone

[tsturm]

[Yellowstone]

tsturm - thanks for the tip - I have used heli-coils before and they worked fine - should turn in well in the Honda alloy. John

[rogerar]

TEF -GEL is made for using stainless fasteners in aluminum.
Roger

[Chester]

Avoid the anti-seize made with copper.