87 evinrude 225 only 4800 rpms?

[bignefan]

I just got a 1986 Sportscraft 190 Fisherman,this boat orginally had and I/O and was converted to an outboard.They put a bracket about 24" of the transome and a jack plate to lower and raise the motor.It has a 87 evinrude 225 on it 25 " shaft. The motor is raised as high as it can go and I think it still sits low.it has a 14.25x 19r 4 blade prop on it. when you WOT it jumps out of the water and plane in seconds it runs 4800-4900 rpms empty about 45 mph. I know the set up is probably completely wrong but it was bartered for work all ready completed. I done want to hurt the motor by low rpms. to be honest it could be a linkage problem, but it think a 4 blade prop was just thrown on . I need to start somewhere so I figured props would be my best bet. Ive triied trimming it if I raise it any bow goes up and it slows

 

[steelespike]

Re: 87 evinrude 225 only 4800 rpms?

Observe the antivent(cavitation)plate at speed usually should be visable.
Use a straight edge to measure the plate height in relation to the bottom of the boat.Difficult with that setup. The stern mount should allow a few inches above the bottom.I would think a 19" would allow more rpm.I'll do a little research.

 

[bignefan]

Re: 87 evinrude 225 only 4800 rpms?

thanks any ideas would be helpful

 

[steelespike]

Re: 87 evinrude 225 only 4800 rpms?

Your boat is about 2400.Unless it has a very deep V bottom I think your speed should be over 50 you probably will need more prop as well.

 

[bignefan]

Re: 87 evinrude 225 only 4800 rpms?

yeah not a deep v .by more prop do you mean less pitch?

 

[bignefan]

Re: 87 evinrude 225 only 4800 rpms?

I currenty have a 4 blade 14.25 19 pitch prop I need to gain about 500 rpms and plane quicker any ideas this is the prop that was on it I'm not happy with the performance and don't want to do any damage to the motor

 

[trendsetter240]

Re: 87 evinrude 225 only 4800 rpms?

I currenty have a 4 blade 14.25 19 pitch prop I need to gain about 500 rpms and plane quicker any ideas this is the prop that was on it I'm not happy with the performance and don't want to do any damage to the motor

What manufacturer and model is the current prop?

Is it stainless steel or aluminium?

What is the gear ratio of your motor?

Have you checked that all the carb butterfly valves are opening fully and in synch?

Once you have determined the above it will be easier to help you pick a prop.

Cheers

 

[bignefan]

Re: 87 evinrude 225 only 4800 rpms?

It is a solas aluminum.The motor is an Evinrude 225 1987 It seem all the butterfly are fully open. Any thoughts or help is apprecited

 

[hwsiii]

Re: 87 evinrude 225 only 4800 rpms?

Fan, you have gotten some very good advice from the previous posters. From running some preliminary numbers it appears you also have your carburetor problems fixed.

If you will read the following and also do the exercise on finding the height on your anti ventilation plate I think we will be able to help you a lot more.

http://forums.iboats.com/showthread.php?t=369057

I also show your recommended max RPM to be 6,000 and your gear ratio to be 1.86:1, please verify this.




H