115hp Merc "racing"

[gdchappell]

Running planed out, in deep water w/ no obstructions, at no particular rpm (but usualy cruse at 3500rpm) the motor will sometime race wildly while the boat slows and falls off of plane. My immediate response is to drop the throttle. After a little head scratching, I get back on the throttle and everything seems OK. I swear, if this was a car, I'd think the clutch wsa slipping! The 2stoke 115hp is a year 2000 model. Thanks in advance!

 

[mistermoon]

Re: 115hp Merc "racing"

Could it be cavitation? Try trimming the motor down when it "races" and see if that helps get the prop reconnected.

 

[emckelvy]

Re: 115hp Merc "racing"

Or maybe it's a bad prop hub letting it spin? <br /><br />Might also be a problem with the hull, or motor setup too high on the transom for the application.

 

[Spidybot]

Re: 115hp Merc "racing"

What are the details? <br />What prop, <br />rpm @ wot, <br />boat make & model, <br />load, <br />hull shape?<br /><br />Put aligned marks (ie. permanent ink marker) on the prop shaft & on the prop hub. Then go for a test drive. If the marks are no longer aligned, the prop is spinning on the hub.<br /><br />I used to have the very same problems + ventilating on even the slightest turn. Got another prop and it solved all.

 

[quantumleap]

Re: 115hp Merc "racing"

Sounds like a spun prop, but it would do it on take off too if the hub was bad.

 

[gdchappell]

Re: 115hp Merc "racing"

UU... Here are the best answers I can provide...<br />prop - factory aluminum 3-blade<br />max rpm @ wot - 5200rpm (I think..)<br />make - 19' year 2000 Key West center console<br />load - 2 men and light fishing gear<br />hull - deep "V"<br /><br />I'll try marking the hub & Shaft next trip out.