How to run an outboard boat motor?

Question

I've got a 35hp Mercury on a 15' bassboat. Is it bad for these motors to be ran WOT for extended periods (10-15 minutes) or are they suppsoed to be ran at 3/4 or 1/2? I'm new to boats and don't want to s***w this things up. BTW its a 80' something 2stroke.

Answer 1

2 stroke engines love to run WOT.  You'll get a lot less carbonizing of the cylinders and much less gumming up of the carburetor.  Your engine does not seem oversized for the boat,  which is usually the problem in trying to do this.  So be sure you have the right oil/gas mixture and run it wide open.   4 stroke engines however, are best run like car engines at no more that 1/2 throttle for long periods.

Answer 2

go to the Mercury web site and look up the specs on your motor. look for the hoarsepower curve or graph. It will show you where the max HP. snd Torque are reached. look where the two overlap. then check where this is on the rpm scale. that is the boats most comfortable place to run.

Answer 3

Yes it is bad to run them at wot for any length of time, especially as they get older. That is if you want to keep it for any legth of time. 3/4 throttle is fine as is a short blast to wot (less then a minute) to get it up on plane or to pass or just to enjoy it! Make sure you have the correct oil mixture!

Answer 4

A two-cycle motor is tuned and set up to run at wide open throttle. If it is propped correctly it will run for hours without any problems. The RPM's should not exceed 5500 RPM's. If you have a tachometer you can keep an eye on it that way. If you don't have a tach you need to take it to a marine dealer to make sure that it is has the right prop. I have a 135 on my boat and I have ran it at WOT for more that 3 and 1/2  hours up the inter-coastal water way before and had no problems. However, at WOT it does burn more gas so the best bet to to back it off just a little to around 4500 RPM's. You will get almost the same speed but use a lot less gas. Think of it like a four barrel carburetor on a muscle car engine. WOT keep the four barrel open and burns more gas. 3/4 throttle get about the same speed but burns less gas.

Answer 5

You have one wrong answer and several good ones.  Make sure you are propped within the specified range, per the manufacturer.  Most outboards like 5000-5500 rpm at WOT.  If you can not turn this high, you are overpropped.  If you are exceeding this, you are under propped.  These engines are built to run wide open.  New Evinrude designs get barge tested (pushing against an immovable pier) for 300 hours at WOT just to meet minimum design criteria.  For a two stroke, 5500 is pretty sluggish, and that's why outboards last for decades.  Jet skis and snowmobiles, using very similar components, live at 7000-8000 rpm most of their lives, and still get hundreds of hours.  So go ahead, blast it.  It won't hurt the motor, just your fuel bill.