Hole in the crankcase

[Ramon289]

One of my 200hp 4 stroke outboards just developed a hole in the crankcase and saltwater leaks out. It is about 3/16" in diameter. I always flush my outboards after running them. The hole is in the area where the thermostat sits (I can see the thermostat spring through the hole). Any ideas what may have caused this? Can this part be welded?

[boscoe99]

It is due to corrosion. You are lucky if saltwater has not sprayed down all the electrics and made a mess of things.

Quite possibly it could be welded but getting access may be difficult.

What do the other thermostat bores look like? Were the bores inspected each time the thermostats were removed, which should have been at least once a year?

More than likely you will need a new block. What is the age of the motor? I would guess that it is 2006 or earlier.

[almetelo]

That usually happen when anodes of the block are not changed (yours may be a diferent case)

I know F75_F80_F90 and F100 blocks are very critical with that anodes if not changed and for sure many other models

here that kind of repair with a new block does not worst it but I know a guy that payed 5000€ +/- $6300 for a new block for a F100 plus labor and other parts ( with that money could buy 2 (or almost) used motors on good running conditions) and even keep the damaged motor for spares.

Good luck

[boscoe99]

The thermostat has copper in it. Copper can be death to aluminium.

I have seen this damage many times in F200/F225 models (mostly older ones) and always thought that somehow the copper in the thermostat, being in close proximity to the aluminum block, was somehow contributing to the problem.

When folks ask about buying a used F200/F225 I try and always recommended that the thermostat bores be inspected. If they catch the problem early enough some have been able to use an epoxy to repair the damage before a hole gets eaten in the block.

Perhaps this damage results also from folks that don't flush their motors. Copper near aluminum with saltwater impinging on both might result in galvanic corrosion. As I said, it can ruin the entire motor. Not only does saltwater spray everything down on the motor, ruining all of the electrical stuff, but that saltwater gets ingested into the intake and will ruin the inside of the motor as well.

[rodbolt17]

don't know if I have any good heads left, I do have a couple F200/225 blocks left.

[greasyshaft]

I guess when you flush the engine, the freshwater has no direct path to flow freely through the thermostat area. Perhaps having these damp salt deposits left behind bridges that gap between copper and aluminium.

There is also a small Anode in the thermostat cover(at-least in NZ), checking the anode when doing the thermostats would be a good idea.

Most of the time doing the thermostats is put in the too hard basket, for many.

[TownsendsFJR1300]

For the current problem, welding is a possibility(PIA) but should be do-able.

As that area is NOT under undue stress/heat, I would clean away the corrosion to bare, CLEAN aluminum.

Scruff it up some and tape off the area for some good, marine grade epoxy and start building up.. A bunch of carefull filing (wether welded or epoxied) should take care of it..

BTW, I had an old Mercury, (about a 90 HP, given to me years ago with issues. Pulled the water jacket cover(above the spark plug holes) and found a hole straight thru from the combustion chamber to the water jacket. Clean it out real good, made a small aluminum plug and had it welded in the hole. Worked great, strong runner!!! Bought another hull, mounted the engine and sold it.


Just curious re flushing.. Do you flush with muffs, the top hose only or?

[almetelo]

Here in PRT seems to be a good place for a marine mechanics

99% of motors run on salt water and for sure more than 95% are not flushed and most no even 1 time...

Many boats are on anchorage and not have fresh water around.

Even the boats that are on marinas with fresh water the owners in the end of a day of boating completely wash the boat very carefully but almost (just for don´t say NEVER) never flush the motor.

Doesn´t left much to do unless change anodes...

[Ramon289]

Hole in the crankcase

Thanks to all for your replies. Good ideas for additional checks and diagnostics. Here is some additional information.

This is one of the twin '03 Yamahas on my Angler 2600 center console. If I remember correctly, they had close to 300 hrs when I bought the boat used back in 2010 and are now reaching 600.

My son and I use it mostly on weekends (guesstimate 6-12 times / yr) and flush the motors when we take it out of the water at the end of the weekend, so it may be in the water one day or two before it is flushed. Some times we tilt them out of the water but not always; did not realize this made a difference. When we first bought it, we flushed with muffs only; about a year or two ago we started flushing through the top hose as well. About three years ago we started using a flushing aid (salt-off). The prior owner told me he ran water through the top hose every time he took it out of the water. We have been doing maintenance every 100 hours (happens every 1 to 1.5 yrs). Maintenance includes replacing t-stats, oil and fuel filters, motor oil, transmission grease, trim tab and tilt base anodes, spark plugs, water pump kit; pump housing every other time. I learned a few months ago about the block anodes and asked my mechanic to replace them during the upcoming maintenance (now); have not replaced them since I own the boat and not sure whether the former owner did. I will share with the forum the condition of the anodes when we replace them.

There is definite build up of salt in the t-stat housing area as a chunk popped out when I had the hole event this last weekend. The hole appeared suddenly, not a small pinhole that grew over time as far as I can tell. The copper bridging hypothesis is interesting and could explain similar failures I have read about in other forums. I will ask my mechanic how good an inspection of the t-stat housing he performs as he has never provided feedback on this particular issue.

My mechanic had arranged for a welder to fix the hole tomorrow using heli-arc welding. But I cancelled earlier this evening when a friend cautioned me that arc welding right in the powerhead could potentially damage other components. After reading more threads in this and other forums I am now inclined to go the aluminum reinforced epoxy route.

The minute I saw the failure, my main concern became the extent of the corrosion. Besides the t-stat housing area, where else should I look to determine the extent of the corrosion damage? I know now a brand new crankcase costs roughly 3 thousands; is it really 5-6 to do the entire repair? This seems unjustifiable in my mind for a 11-12 yr old motor.

[TownsendsFJR1300]

On my current F150, I flush with the upper hose for 10-15 minutes once at the boat lift(I'm on the water). I then run it on the muff's for another 10-15 minutes so the engine can warm up, the thermotat open and water gets fully thru out the engine; http://s176.photobucket.com/user/SRT...ff81b.mp4.html

My neighbors 200 2 stroke (he rarely flushed) was having overheatig issues. We eventually found about 4" thick SALT around the lower two cylinder water jacekts (besides elsewhere).

Just looking thru the thermostat opening and the issues you currently have, I would strongly consider the below procedure which seems to be pretty effective..

As a side note, on my old 2 stroke Evinrude(loud), when I used muffs, never had an issue, original thermostat. Once they came out with the upper hose flush attacment, I just used that. Not long after that, I had thermostats corroding up, etc. IE, IME, running the engine with muffs if possible, gets more salt out.



Some interesting reading to head off later potential issues;

http://www.yamahaoutboardparts.com/f...g-th19434.html

http://www.yamahaoutboardparts.com/f...m-th23666.html