Spun hub?? Something worse?

[Riverrat43]

1979/80 Evinrude 25 hp elec start....Boat is a 14ft fiberglass old, old Kennedy Craft, V hull, open (like a Jon boat) fishing boat, approx 250 lbs empty. Prop is 2 week old 9.2x12 3 bladed stainless. Motor is mounted with the cav plate even with the bottom of the boat and the mounting bracket is fully down on the transom. Short shaft motor and fits the transom height fine. There is a doel-phin attached to the cav plate in the proper manner. <br />My son and I have taken the boat out 4 times in open water. We've determined that the rig runs best with the pin in the 3rd hole back when both of us and our gear is on board. (about 600 or so pounds or in addition to the boat and motor). It planes out nicely and does about 32 GPS mph. (no tach). With just one of us, it runs best in the second hole..about 39 GPS mph. Gets on the plane quickly and runs great. Have never run aground or hit an object. Now the problem:<br />Yesterday we took it out and right off the trailor it would not get on a plane...it sounded as though the exhaust was out of the water, the rpms were high with the whole sound and feeling was like we were cavitating or the prop was blowing out. Thought the weight distribution needed changing..no help...dropped the pin to the second hole...no help, dropped the pin to the first hole... same symptoms. It would go along at trolling speed, with an ocassional "missing sound" like the prop slipping, but when the throttle was increased, the "cavitation like" problem occured. RPM's went up...no plane, no speed. Could this be a spun hub? It's a new prop,(NOS..New Old Stock.. I suspect) is this common? Any ideas?

 

[rickdb1boat]

Re: Spun hub?? Something worse?

Not common for a new prop, unless you hit something. But it could be a spun hub, cause that sure sounds like all the signs of one. Do you have the old prop you can try out??

 

[Riverrat43]

Re: Spun hub?? Something worse?

No...I bought the motor used and the old alum prop was toast..bent and chipped. Changed all the seals etc. in the lower unit when I got it...all the gears and the clutch dog looked good. Changed water pump and impellar as a matter of course.

 

[ob]

Re: Spun hub?? Something worse?

You'll need to either perform a close visual of the prop hub or better yet mark a line of reference from prop hub to barrel and note whether the marks stay aligned after a failed run episode.Sounds either prop related or you have a slipping issue with the gearing in the lower unit.Worse case is failing driveshaft splines .

 

[G DANE]

Re: Spun hub?? Something worse?

You have an amazing top speed with a 25HP and a 14'.

 

[Hooty]

Re: Spun hub?? Something worse?

I think like G Dane. With that prop, 1.87:1 gear ratio, 10% slip and 39mph, you're spinnin' that engine in excess of seven grand. <br />Post back and lettus know what ya find.<br /><br />c/6<br />Hooty

 

[Riverrat43]

Re: Spun hub?? Something worse?

Visually inspected prop shaft splines and the splins on the inside of the prop hub. They look OK..sharp edges as opposed to rounded off ones. Can't run it for another week or so, but I will take the prop back where I got it and see if they can tell me if the hub is OK or not. By the way, about the speed..I left out a couple of things pertaining to that and only included it to illustrate that is was running fine on the prior outting. Speed was GPS...no gear..just me and then me and my son...down river on about a 4-6 knot river.( didn't subtract for that). Also, the motor while mounted even with the top of the transom, is mounted 6 inches behind the transom on a jack plate. This (along with the doel-phin) allows me to reach a plane quickly and then back off the throttle and stay on plane at speeds as slow as 12 mph...saves on fuel. Runs in really shallow water and handles a lot better than with out the plate and the fin.

 

[Riverrat43]

Re: Spun hub?? Something worse?

Udate:. Took the prop back where I bought it. I asked the guy if he could check to see if the hub was spun. He asked why I thought it was so I explained. He just handed me a new prop and said, " you're probably right..it's spun". Then he looked at the old and said that the hub looked "pushed out", even with the housing and on the new one the hub is indented. Again he said, "hmmm." "Bad Prop." Told me to have a good day and let him know how this one worked. Nice to find a shop with customer service like that. Will put the boat back in the water this week end and see if that fixed the problem.