[Kajundave]

Originally Posted by chasin'tail

How old is the motor? if it's close to 10yrs, think about the head plate galley areas being clogged up with crud. I have a 115 yamaha that did the same thing, chg water pump, checked thremo-stat. I pulled the heads off and found what a mech. said would be there. I cleaned the galleys, if you do it use plastic scrapers so you don't damage the metal. New head and water jacket gaskets and your back in business.

I would have said a blown head gasket but...
[SIZE=3]Mine did the exact thing, it did it consistently on long runs, horn would sound, I would stop no steam, or extreme hot water exiting the engine, let it idle for 2/3 min and the horn would go off, it just kept getting more and more often. When or if you remove the heads you will probably notice one or two bolts loose, according to Yamaha you are supposed to re torque the heads after X- amount of hours, I re-torqued mine and the problem went away, after a few trips with no problems, I replaced the head gaskets anyway. This was on a Yama saltwater series 250hp[/SIZE]