Yamaha F250 Oil Leak/RPM issue

YachtaFun

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Curious if anyone has any ideas on my 2006 F250 issue on my Marlin. Have had a call out to my mechanic, but been a week now and they havent had a chance to look at it and are backed up... so heres whats been going on:

Boat ran great once launched. Then after third run of the year, noticed large oil sheen from stbd engine and the engine well had a lot of oil leaked into it after trimmed (like a qt). I then searched all over for a leak while it was running, and there was nothing obvious i could see, but engine had oil all over. Only weird thing was the breather tube on top had come off (not sure if that has that much oil run through it). I then ran it at the dock a couple times and trimmed it, and never saw substantial oil again. Went for a quick sea trial, and it ran well, no oil leak after or anything. Figured the breather tube must have been the issue. Then I went on a trip saturday, and 25 min into cruising at 4500rpm, stbd engine rpms started dropping, all the way down. For the rest of the 2hr trip, stbd engine woudnt go above 3500rpm, but at that rpm it ran fine, port ran fine a 5,000, and no major oil leak that I could see on stbd. When I got back and trimmed it, engine well had oil in it a couple hours later. One thing to note, is last owner had the oil pump on that engine replaced 3 years ago. any ideas??? thanks as always.
 
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seasick

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Did you check the oil level? Was it going down?


If you saw oil on the water, but the level didn't drop I would be concerned. If the level did drop I would be concerned but not as much as the first case.
If you have a bad drive shaft oil seal, that could explain things. The fact that the motor only made 3500 revs may be it telling you that the oil pressure was low.
If the oil level is increasing that could mean water or potentially gas in the oil. Loosing oil or water in the oil could also be an oil pan problem. (corrosion issue?)
Hopefully you have something simple but I would recommend that you do not run that motor without finding out what is goin on.