Synthetic oil experiences with Indmar engines

I'd like to hear from people who use synthetic oil in their Indmar engine. If you want to debate the benefits of synthetic oil, please start a new thread. I'd like to hear from people that have actually had experience with fairly new Indmar 350s. The main reason I ask is because my BMW experienced trouble maintaining a steady idle speed when cold after adding synthetic oil. (I'd let off the throttle and the engine speed would drop down too low and then oscillate up and down as it tried to reach idle speed.)

Thanks.

Your BMW had a vacuum leak, bad 02 sensor or a bad idle air control valve. When the IAC gets lazy they hunt for idle and stall. I just got off the phone with a customer complaining of that. I am now running synthetic in my truck because I am lazy and do not want to change the oil as often.

No problem with 15-50 Mobil 1 in my '98 Indmar 5.7L in a MasterCraft Maristar 210. I change every 50 hours and waited until 100 hours to change to synthetic. The boat has about 300 hours now. Runs well, idles nicely, no leaks. No problems with Mobil 1 5-30 (winter) or 15-50 (summer) in my E39 5 series with over 100,000 miles. Some of my BMW purist friends say I should be using the 5-30 year round but, like the battle over synthetic or not, that's another topic.

260h on my Indmar and not a single prob. Very smooth. use mobile 1 in both my boat and truck.

Put over 700 hrs on my 92 mc 205 and ran mobile one and pulled the valve covers off when I sold it and the engine was like brand new. Changed it every 50 hrs. Used it in my yukon and my lightning also. Do not use it on a old motor though.

ran all season with only a yearly oil change.Averaged about 130 hrs a season.Never had a problem and it actually looked clean at time of change.Ran synthetic redline oil for the tranny.same good results.Indmar and velvet drive components.

If you change you're oil every 50 hrs synthetics are a wom imho.

Although I did say "If you want to debate the benefits of synthetic oil, please start a new thread", I got the info I was looking for so let's debate!

My BMW increased its gas mileage by about 2MPG average when I changed to synthetic. In my opinion, anything that reduces friction enough to get a 10% increase in fuel economy has to reduce the engine wear drastically. If your opinion is that you sell your boats before it develops any engine wear, that's a valid point. If you're saying that an engine will last indefinitely as long as you change your oil every 50 hours, I think that's just crazy talk.

I bought mine used. If I want to start using synthetic do you have to pretreat the motor in any or merely change the oil as normal and add synthetic.

I have a question. Don't BMW's come with synthetic oil from the factory. I know that that's what my dealer uses in our E46. It actually says to use BMW or Mobil 1 synthetic oil in the owners manual. I run Mobil 1 in my boat and have never had any problems.

im curious what the indmar parts are in a chevy block?? i thought the inside was pretty much the same from chevy boat motor to chevy boat motor and only the ancillary components and fuel system were different??