4-108 in warm water is nothing new apparently. The remedy is not my idea but came at a opportune time. I was having a hell of a time with it heating at anything other then a medium speed. A friend suggested that I install an additional heat exchanger but I wasn't convinced that it could be so simple and I didn't want to go to the trouble and expense of having one shipped down. He was so sure of him self that he took his heat exchanger off his engine and brought it over. We ran the hoses and just left the thing laying under the engine and off we went. I was getting ready to come back up the Baja and that's why I was trying to eliminate any heating issue because I knew it was going to be a long hard couple of weeks. It worked and my friend decided that instead of flying to Washington from Cabo he would come up the coast with me with us using his heat exchanger then fly from San Diego. I think he wanted to keep an eye on his heat exchanger Anyway, when we got to SD we took his heat exchanger off and boxed it up. He had it serviced while he was in the US and reinstalled it when he got back. I bought the second one and installed it on the bulkhead and all is good. It's good to have friends.