Engine slow during break in.

[uffeh]

I recent bought a brand new 5 HP, 2 stroke. I am in the process of breaking it in, and have followed the instructions in the manual; 25:1 oil mixture, idle for 10 mins., then run slow for 1 hour, then run at max speed for a few seconds then slow for 5-10 minutes etc. My problem is that the engine seems very slow. There is no noticeable difference in power between 50% and 100% power on the tiller handle, and I can't get the boat planing (its a small inflatable) even with only myself in the boat.

The dealer didn't seem to know, but told me to wait until after the break in is complete to see if it speeds up after that. I am trying to understand if there is a technical reason why the engine would not be able to rev to higher rpm's during the break in. Is there some mechanism that prevents it from doing so to protect the engine. Can the increased amount of oil in the gasoline have something to do with it? Could it be a problem with the engine so I should stop breaking it in?

Appreciate your opinions.

[tripleb]

Hello uffeh,

Could be the prop size. After break-in, tell your dealer to put on a smaller diameter prop and see how the motor does.

[uffeh]

This is the prop that came with the engine. Surely they would include a prop that would work well with a small boat? I'm more concerned that the engine has a problem, and perhaps I shouldn't continue to run it in case that makes it worse...

[tripleb]

Hey uffeh,

Whether it is the prop that "came" with the motor or not is not the real issue. The issue is that a prop should be selected to allow the motor to reach close to the full RPM range on a particular boat.

Your Yamaha dealer should have test driven your boat checking the RPM's with a shop tach.

[jamfordz]

check if the cavitation plate on the outboard is in line or just below the lowest part of the dingys transome...you may need to ajust the height of the outboard in relation to the transome of your boat....the new 15hp I had on my Zodac was good to go from day dot....

regards Jamie

[Ken]

uffeh,
I agree with tripleb in that you may have the wrong prop for your application, but you should hear and feel quite a bit of difference from 50% to 100% throttle. I think there is something wrong with the motor.
Take a look at the throttle linkage from 0 to 100% and see if the carb linkage is moving thru its entire range. Actually, this is something the dealer should be doing. Also, spark advance should be looked at.
Running double oil during break-in would not cause the symptom you are describing - just a lot more smoke than normal.
Good luck [img]smile.gif[/img] ,
Ken K