How many RPMs should I run my 90hp Yamaha?

Hey, guys. I picked up a lightly used boat last weekend and I am wondering how many rpm I should be running at. When I open her up I get up to about 4500 at three quarter throttle and then when I push to full throttle I get to about 5000. The outboard is a 2007 and was broken in by the previous owner, I just don't want to run it into the ground by doing something I shouldn't. My boat is about 1800lb loaded and at 4500 is hitting about 30mph. This is what I want to know:

• Is 4500 rpm pushing the boat to 30 mph about right for that size boat, or should something be tweaked to give me a little more speed at those rpms?
• Can running the boat at full throttle cause problems down the road?
• Is there anything I should keep in mind when accelerating; can I push it straight to 3/4 throttle or should I increase the speed gradually?

Sorry if these questions seem a bit elementary, this is my first boat and I want to make sure she stays happy.

Thanks for the help, guys; it's much appreciated!

Re: How many RPMs should I run my 90hp Yamaha?

As long as you have a good strong steady stream of water coming out of the tell tale when at WOT, a topped up oil tank and a regularly WELL maintained service done at a GOOD Authorised Yamaha service centre (including checking of fuel tank to motor fuel supply, filters, free flowing hoses and primer bulb etc).......give it heaps and happy boating

Re: How many RPMs should I run my 90hp Yamaha?

P.s..Talk to RODBOLT about your E-10 fuel you have there in the states........very important from what i have been reading on here

Re: How many RPMs should I run my 90hp Yamaha?

The first thing you need to do is post your exact model number. 90 hp motors were made in 2 and 4 stroke versions. Without knowing the exact model number you cannot receive a good answer. The next thing you need to do is to call up Yamaha and order a factory owner's manual and service manual. You should not be operating this motor until you have read the owner's manual. Here is the link for finding your correct manual:
http://www.yamahapubs.com/html/year_outboard.jsp?type=OB

Re: How many RPMs should I run my 90hp Yamaha?

Thanks, BruceAML. I have the manual and have read it from cover to cover (a few times actually). There is nothing in it that tells me how it should push a boat of 1500lbs, or the recommended RPM (it only discusses how to break it in). It also doesn't mention anything about how to accelerate a boat as to not cause harm to the engine over time, or if running a boat at full throttle will damage an engine over time. To be honest with you, I searched all over the place after reading the manual and came to iBoats as a last resort. Any help would be greatly appreciated.

It's a 2-stroke and I can't tell you the model number because it is currently dry docked in a Marina. The only numbers on the manual, which I am assuming is for a few different model numbers, are LIT-18626-06666-96 and 6H1-28199-17.

Hope that helps.

Thanks!!

Re: How many RPMs should I run my 90hp Yamaha?

The factory recommended operating range is listed at 4500-5500. The 90 hp 2 stroke is a very robust engine. Smooth acceleration is fine if that is your preference and that is probably the easiest on the motor. In my mind, the most important thing is to use a top quality TCW-3 oil and follow the maintenance schedule. I think you should post the size and pitch of the propeller and go to the propeller forum for the correct size for your boat.