Oil Dilution

[GS]

I ran new twin 2005 F115's up North with continuous problem of dirty oil and oil dilution with no Yamaha mechanic available. Now about 5 oil changes/engine. Have been filling halfway on dipstick and wait until full to change. Spoke with Yamaha and they suggested numerous possibilities such as over propping, improper break-in, carbonization of cylinders, running too cold. Maximum RPMs about 5700 and themostats functioning properly. Finally got it to dealer and they say everything fine as far as they were concerned with cylinder compression good, suggesting problem is bad fuel. Unlikely in my opinion because many Yamaha's up there all using same fuel and I am the only one having problems. I suspect the engines are running too cold with improper combustion but mechanics know nothing about this problem even though I have read about it on a couple forums and read rumour of a Yamaha fix "as needed" involving different themostats, ECU and spark plugs. Can anyone help with this? Thanks.

[lectricchair]

Hello. I spent a good amount of time with the same problem on my 04 F115. I made several oil changes and a few spark plug cleanings/replacements in the first 100 hrs. until I found some interesting results/fixes. First, at my 10/20 hr. check, my dealer replaced the thermostat from 140 degree to 160 degree (if you look up the thermostat values you will notice the F115 is the only 140 degree in the inline 4 cyl.-four stroke line, others are 160). Second, on the same warranty claim, the dealer changed the heat range on the plug up from LFR 6 A-11 to LFR 5 A-11 (the 6 is colder than 5). The 'makin'oil' problem improved. Third, I had the dealer do a lake test and with my rig we decided a 19p prop was a better choice than the 21p the boat was delivered with. This allowed me to run 5900 rpm on the pad with a moderate/light load vs. 5700 or so. Not long after this (around 300hrs) we decided to do a shock dose of ring free and blow it out. That stuff works and, from new, I always ran a normal dose which probably saved my arse due to the motor running a little too cold during break-in. *****ing is still a minor problem that adds a little dilution to the oil but I always try to run hard the last couple of miles toward the ramp on my way in and I can see on the oil stick that this tends to evaporate/burn off the small amount of oil level gain. Cold weather up north has to be an oil dillution problem for some F115 owners. I'm in central Texas. I'm now at 460hrs. and had two oil analysis done during my last oil change interval (safe than sorry). Both are normal, wear metals are well within spec, gas dilution on both is less than 1% by volume. The first sample was a reference sample with 21hrs on the oil (418 on engine) the second was taken around 52hrs. on the oil (449.5 hrs on engine). This time period represents my late fall 06 thru early spring 07 fishing trips here on Lake Travis. I still changed the oil since I was pushing the 6 month change interval. IMO running these engines hard after *****ing if the engine operating temp is up to 160 or so will keep your oil level in check. Sorry this has been so lengthy, but I was very concerned about this within the first week after I bought this new tecnology outboard, but in hindsight it all makes sense, at least to me. Boat info: 2005 G3HP 180/F115/19p prop/all the way down on the transom (no jack plate)/wot 5900rpm/52mph or so, light load. I truly hope this will help others understand the situation regarding the Making Oil issue. All of my hour readings were from Yamaha pt. # eng-meter-4c-02 (worth every penny). And... Amsoil is a good source for oil analysis if you need to check your wear and dilution situation, although I still run Yamaha 4M oil. One last note: A small level placed on the lower unit cavitation plate will allow you to keep accurate oil level check notes. It's pretty easy to misread the stick without this inexpensive tool. PK