engine vibration around 3100 RPM

[dfg4240]

Hi
I left seneca lake and went about 70 miles to the port of oswego and then another 55 or 60 miles to the genesee river where it empties into Lake Ontario.
The engines ran beautiful and cool all the way around 20 MPH form Oswego to the river.
When I pushed her to the 3000 range,I felt a vibration in one of the engines and backed off to 20 MPH all the way.
Today I was down to the boat and took off the wood trim from the upper station and the step ladder from the swim platform and tomorrow I will remove the swim platform.
There were some people looking at my boat from Shumway and said it looked beautiful compared to when they pulled it from the water.They were bringing another boat inside.One was a service tech and they thought it was a repaint but it was the original but I just buffed and waxed everything.I was talking to him about the Vibration in one engine on my way down here and he immediately went to the back of the boat and look at my props and said there is the problem.
I didn't see any chips or dents but he said they need to come off and be reworked. He said there would be a big difference in smoothness and rpm.
I looked up props and saw that a new one is around $800.
Does that sound right. I will try to take some pics but it is not very bright in there. Whoever cleaned the outside the last time did a terrible job.The boat looks like new except for the bottom which can go at least another year or two before a repaint.
dfg4240

[dfg4240]

I just remembered that I think the prop size is stamped on the prop itself and if I remember somewhere that they were 20X21 props which means 20" across the prop and moves 21" in one revolution theoretically. I think that is what it means.This is for my F36 with 440 engines.I never found out what the top speed or RPM was but I have an owners manual on the way to me now. I bought it from beacon marine.
anybody have them reworked? He said the port side definitely but better take them both off and have it done. I saw a canvas guy there also and asked for an estimate for an enclosed rear with windows and screen and also one estimate for just an overhead type without the sides just to get out of the rain.
It would extend to cover about 3/4 of the rear deck.
dfg424o

[Paul]

I use Johnny's boat propeller in Detroit. They've gotten rid of vibration for me in the past and also provide you with a copy of the prop scan which shows where each blade of your prop is in relation to the allowable tolerance.

Check out the attached link.

http://www.johnnyspropeller.com

[gitchisum]

I've had some vibration in mid 3000 this summer. I asked my mechanic to check and he found the bearing in my shaft strut was sloppy. Not saying yours is, but would be worth a check.

Whomever you use for your props, Hale MRI is worth the cost plus some! Basically hot knife through butter after that!

[dfg4240]

OK thanks