Honda BF 25 Blown Head- manufacturing fault or just a dud you be the judge?

[snapperman-nz]

I have a honda bf 25 with a blown head. What happened is I took the boat/ motor to our local dealer to have it serviced. They advised that they couldn't remove the sparkplugs (2) out of (3) due to at that stage what they thought was overtightened plugs from a previous service at another dealer. They advised that the head should come off due to the problem and be sent to a reconditioner to have the plugs removed. The reconditioner removed the plugs carefully and helicoiled the threads. They also advised the plugs were not overtightened they were corroded in. Which they hadn't seen before on these heads. To cut a long story short. There is appears to be a moulding fault in the alloy around the sparkplugs. The alloy is too thin on one side, what has happened is this has developed a pin hole from the water jacket onto the sparkplug thread causing corrosion. Not detectible by the eye. What has happened is the alloy has not held under the new helicoil and pours water straight in..

Has anyone struck this before? and does anyone know where I can get another head from

Thanks Snapperman.

 

[Frank Martin]

Re: Honda BF 25 Blown Head- manufacturing fault or just a dud you be the judge?

Have seen this many times before on all aluminum heads with long reach spark plugs not just Honda power

a couple drops of gear lube or a dab of wheel bearing grease on the spark plug threads will greatly reduce the chances of this ever happening again
Never install spark plugs in any aluminum head with the head being warm
Remove and relube the plugs once a year in salt water applications every couple years in fresh water
If you can not find a used cylinder head it?s probably not worth fixing
Don?t bother with heli coiled plug heads they seldom work
I have used a machine shop that puts the head in a oven and pre heats it before removing the plug with a socket that has been super cooled in dry ice but even this extreme method does not always work
I would not call this a manufacturing fault, this is a problem when we use light weight aluminum for cylinder heads requires a little different maintainense practices