6 hours ago, MalibuNation said:

I can only add a little to this.  My 2003 came with 15w40 and contacted Indmar and they said 15w50 Mobil 1 was fine and wouldn't void my warranty.

I found this article that was helpful for me to understand oil viscosity and it’s intentional design usage and ratings. https://www.castrol.com/en_us/united-states/home/learn/car-maintenance/oil-viscosity-explained.html
 

From what I gather after reading this, Indmar designed this motor to be regulated to run at a certain temperature range, and requires 40 grade oil viscosity to lubricate the engine’s metal parts at that temperature range, because of the size of the engine’s pathways that protect and clean those metal parts or surfaces.
 

Going with higher viscosity number like 50 will increase resistance and increase fuel consumption but will yield higher protection between metal surfaces.  But, too much resistance is not good and can cause over pressure problems.
 

Going the other way to a lower grade number like 20, will have a lower viscosity and provide less resistance than the recommended 40 grade at normal engine operating temperatures, which also provides less protection between metal surfaces.  So, too little resistance is not good and can cause overheating and wear damage to metal pathways.

As far as my original question to the 15w-40 vs 25w-40.. this article helped me understand that “W” stands for winter and the number in front is for starting engines with less resistance in those cold temperatures.  It’s what makes it a “multi grade oil” that has the ability to allow the oil to have a lower viscosity in cold temperature weather (winter) for starting the engine, and then run at the normal grade viscosity of 40 at the normal regulated engine temperature.

So 25w-40 in a hot climate does make sense as far as having a little higher viscosity on starts for protecting the metal surfaces without the need to be thinner viscosity for the cold weather starts.  The engine still runs in the normal operating temperature range with the recommended 40 grade oil viscosity providing the correct amount of engine protection at those temperatures.  

Thanks, good idea. 

20 minutes ago, formulaben said:

Just spit balling here, but have you checked your transmission fluid level lately?

Yes, the previous owner took it to a local boat mechanic after I complained to him about it. He had it checked out as far as fluids etc. but did not drive it. 

19 hours ago, Steve B. said:

Maybe try his prop on your boat and vice-versa.

9 minutes ago, GAAHTH said:

Did the pump come right out after removing the allen bolts?  Mine may be rusted..can't get it to budge.  drizzling some oil in the seam now, don't want to mess the pump up trying to pull it from the crank pully

 

Sorry, meant to reply but moved past it in my excitement. It literally fell off after the 3 allen bolts were off. I was researching other posts and I think someone recommended a dead blow hammer to the side of the pump, or a piece of wood and regular hammer. 
 

My phone is dying. I’ll try to find the post in a bit. 

Did the pump come right out after removing the allen bolts?  Mine may be rusted..can't get it to budge.  drizzling some oil in the seam now, don't want to mess the pump up trying to pull it from the crank pully

47 minutes ago, rakr said:

Pump off. It was easier than I thought it was going to be. 
 

Update, impeller out with just a wiggle! Sigh, I see a few new additions to the “boat emergency bag” to make this easier.