Doral 164 top end.

[kenmyfam]

I have a Doral 164 with a 1985 140hp V4 Johnson on the back. A 14 inch prop with a 19 inch pitch. It is giving me 46 mph at 5400 rpm (WOT) my previous prop was a 14 inch with a 17 inch pitch. This gave me 45 mph at 6200 rpm. (I still have this prop as a spare) I am hearing of much greater speeds from boats this size with smaller outboards. Question is, do I believe this or is there something wrong with the set up ???? She comes out of the hole no problem, pulls me up on ski's no problem (and I am not a good skier) and appears to be running great. Cruises at 35 mph at 4,000 rpm very nicely. Does not seem to matter how many people are on the boat, it gives the same performance !!! I am very happy with it but reading around I wonder if I should be getting more top end ???
Any thoughts or ideas would be welcome.
Thanks,
Paul.

 

[steelespike]

Re: Doral 164 top end.

Not an expert but::
While this isn't specifically a prop question I think you may gain some help in the prop forum.
800 rpm drop in only 2 inches of pitch seems too much to me.You may want to check the rpm with another tach
And verify your speed with a GPS.
Your new prop may be a more efficient design.which might account for the big drop in RPM.
The 85 140 Developes its power at 5,500 rpm.So it appears you are slightly over propped.
Most allow a small amount of rpm above that rated.
About 200 to 500 rpm.
Someone will surely be along with specifics.
Comparing boats/motors is difficult as weight,bottom design/condition,and motor set up can give signifigant differences in performance.
The antiventilation plate should be about even with the bottom of the boat.The more you can raise the motor without ventilation problems the better your speed.
As little as an inch could result in 2 to 3 mph increase.

 

[kenmyfam]

Re: Doral 164 top end.

Thanks for the response Spike.
Speed is GPS verified and second tach reads the same. One thing that I have noticed is that I can come up to full trim and then I can start going faster by using a little power tilt. Am I too low in the water with the engine to begin with ??? or should I be changing engine to transom angles slightly. Not desperate for more speed but would like to have the set up tuned to its optimum. This prop is cupped and seems a little thicker. It is a genuine OMC prop and my previous one was not cupped and am not certain of the make..

 

[steelespike]

Re: Doral 164 top end.

You may have to make or by some wedges to go under the mounting bracket to give you a little more trim.Perhaps your transom has more rake than some.
Don't forget about raising the motor.
This really works if it needs it.

 

[kenmyfam]

Re: Doral 164 top end.

Will be checking the motor height next time out of the water and will make and fit some wedges over the winter. Or maybe sooner if the weather holds out.
Once again thanks for the input and I will report back with any further news.
Paul.

 

[jimmbo]

Re: Doral 164 top end.

17" uncupped prop to a 19" cupped... 800 rpm drop doen't sound unreasonable. You might want to try a cupped 17". I take it that all these props are Aluminium?

 

[kenmyfam]

Re: Doral 164 top end.

Yes they are aluminum. 17" cupped sounds like a good idea. I will see if I can get one to try out from the dealership and let you all know.