[kkilloy]

I have a 1999 Yamaha F100 HP four stroke outboard. I change the engine oil (10w-30 Castrol and Yamaha brand oil filter) and lower unit oil annually and the engine has performed great. Boat stays in the lake all summer and is used at least twice a week. Last week I noticed motor oil in the self bailing area of the rear of the boat. The oil runs out around the area that the large steering arm connects. It only leaks while tilted. It is very hard to tell where it is leaking. I am guessing about 1 to 2 ounces per week. The engine is very clean and runs beautifully except for the oil leak. Any help would be greatly appreciated.Thanks, Kevin

[rodbolt]

hello does the oil level on the dipstick drop? when you changed the filter did any oil spill?that is a new one as 4 strokes live forever and never break. ask any salesman. some even say they fry eggs bettern tha ole lady. good luck and let me think on this a bit

[kkilloy]

The level on the dip stick does not seem to change a noticeable amount but it has only been happening about three weeks. The oil was changed in the spring and I was very careful to make sure the rubber seal was on the oil filter and it seated properly. I see no oil leaking around the filter. Thanks for the reply. These situations make me long for a pre-mix two stoke. I miss the smell of a two stroke!!

[kkilloy]

The boat is on the trailer now. I checked the oil level and it is about 1/2" from the top of the cross hatch marks on the oil stick. I am going to now tilt the engine all the way up and lower the tongue of the trailer to approximate the level of the boat as it floats in the water to try to duplicate the problem. I will post results. Thanks again.Kevin

[kkilloy]

I went out at night with a flashlight and was able to clearly see oil drip from the oil seal at the top of the drive shaft. Has anyone else had this problem on 4 stroke yamahas and how hard is it to replace. I hope the new seal design is better than the old seal. I am not happy with this type of failure on a yamaha. I think the oil seals used on a 4 stroke outboard should almost never fail because that's like pouring used oil directly in the water.Thanks, Kevin

[rowbards]

The 80-115 had a oil pump problem that the seal was damaged on assembly, some wouldn't show up till engine grew in hours, I have replaced a couple of these and the only indication would be oil dripping from the drive shaft and it doesn't seem to be coming from anywhere under the cowl. The fix would be to remove the powerhead and replace the oil pump. Some of these have been considered for "good will" if you have a dealer take a look and make a call.Hope this helps...Jay

[motojatu]

Originally posted by rowbards: The 80-115 had a oil pump problem that the seal was damaged on assembly, some wouldn't show up till engine grew in hours, I have replaced a couple of these and the only indication would be oil dripping from the drive shaft and it doesn't seem to be coming from anywhere under the cowl. The fix would be to remove the powerhead and replace the oil pump. Some of these have been considered for "good will" if you have a dealer take a look and make a call.Hope this helps...Jay

[kkilloy]

Thanks for all the help and info. The dealer said Yamaha will cover the parts and I will pay about $225.00 labor. Sounds fair to me on a five year old engine.Thanks,Kevin

[ebubeck]

Same problem with a Mercury 90HP 4stroke 2001, powerhead by yamaha, and I'm willing to bet the same oil pump and seals as your yammy. Shame on yamaha.