F250 model year '06

Art Vrola · 07-07-2008, 12:05 PM

I have just under 100 hours on the motor and have never had any problems. This past weekend however, when I hit 4200 RPMs the motor rev'd and jumped to 6200 RPMs. As soon as I brought it down to 3000 RPMs it appeared to be normal again. I ran it up to 4200 RPMs again and again the same thing happened. This only happened twice and it has not happened since. Did I spin a prop? Or is it something else I should be looking for? I was running in the bay so its hard to believe it was due to cavitation, but again, this is the first time I've experienced anything unusual with the motor.

A1 Outboard · 07-07-2008, 02:52 PM

Most likely the prop hub spun loose. Sometimes when that happens, the melted rubber re-glues the hub tight again for a while. Otherwise there may be an obstruction or tansducer affecting the water flow to the prop, or exhaust gas leaking from around the gearcase to prop seal area or sucking back from the exhaust outlet.

kf08655 · 08-14-2008, 05:52 AM

I have the same problem. I had recently just put on a new prop. I took the prop to one of the best on the norteast(Bossler & Sweezy). They told me there was nothing wrong with the prop. Its odd b/c this didnt happen with my old prop.

A1.. is it possible that this problem didnt occur with my old prop if I were running an oversized one?

Flat calm water it fine once I hit a few wakes it starts revving.

A1 Outboard · 08-14-2008, 06:08 AM

Quote:

kf08655 - 8/14/2008 8:52 AM I have the same problem. I had recently just put on a new prop. I took the prop to one of the best on the norteast(Bossler & Sweezy). They told me there was nothing wrong with the prop. Its odd b/c this didnt happen with my old prop. A1.. is it possible that this problem didnt occur with my old prop if I were running an oversized one? Flat calm water it fine once I hit a few wakes it starts revving.

Your engine may be mounted just a bit too high, some props work better near the surface than others. Put your old one back on and see if the problem goes away.

kf08655 · 08-17-2008, 09:00 AM

A1 Outboard -
I need a little bit more help... As you can see from up above, my engine revs sporadically and I lose speed. We've determined it is not the prop. Here is a new twist- the boat seemed to be working fine as the gas needle was nearing empty. I just put in a little bit more than half a tank of gas and the revving problem came back. Any idea what may be causing it? Is there anything in the 200hour checkup that I might be overdue on that could cause something like this?

Thank you,
Kirk

A1 Outboard · 08-17-2008, 11:48 AM

Engine height?? Adding fuel lowers the bow and raises the stern?

kf08655 · 08-17-2008, 12:51 PM

One problem.. I just put on an "oversized prop" and it worked with no problem. This whole mess started b/c I was running a 21" prop. I was worried that I over propped my boat. I can get the oversize prop up to 5200rpms. Maybe I should try a 19"?

Brett1 · 08-17-2008, 01:36 PM

You may have also picked up a piece of rope or other trash that caused the props to cavitate.