Want more speed

[airdvr1227]

Trying to get some prop ideas.

Prop now is a 15 1/2 x 15 aluminum...not sure who made it
Drive ratio is 1.41
5.8L 230 hp
Boat weighs 3700 dry
Typical operation is 2 - 4 adults

As it is right now trimmed up I'm getting 32mph at 4200 rpm. I think it'll go faster.

Advice please.

 

[wca_tim]

Re: Want more speed

Trying to get some prop ideas.

Prop now is a 15 1/2 x 15 aluminum...not sure who made it
Drive ratio is 1.41
5.8L 230 hp
Boat weighs 3700 dry
Typical operation is 2 - 4 adults

As it is right now trimmed up I'm getting 32mph at 4200 rpm. I think it'll go faster.

Advice please.

after you go through everything and be sure you're engine is running right and in good tune, you may want to reprop to put your wot rpms more like 4600-4800 rpms. (don't know what drive, engine, etc... from your post, see your documentation for max rpm for your engine set up.)

being overpropped can be just as bad as being underpropped.

when it comes to top speed, the primary determining factor (once prop set-up is right) is horsepower. that's a lot of boat for a small engine and is probably never going to bemuch of a speed demon.
did that prop ever reach a higher wot on that boat? is the hull dirty (as in do you keep it in the water?). There's a sticky don s put together that lists things to check if your wot rpm has decreased over time... I'd start there.

 

[airdvr1227]

Re: Want more speed

WOT acording to the OMC manual is 4200-4400. This is my first season with this rig so I don't know about how she performed in the past. Hull isn't dirty and she just had a tune-up.

You think 32 is all I should expect?

 

[Randybeall]

Re: Want more speed

WOT acording to the OMC manual is 4200-4400. This is my first season with this rig so I don't know about how she performed in the past. Hull isn't dirty and she just had a tune-up.

You think 32 is all I should expect?

Unfortunatly you are at the point of no return for changing props. If you are turning 4200 now you are just about perfect for that engine. Have you tried moving weight forward or aft in the boat to see if it makes a difference? I am hoping you have tried running the trim up and down while at speed to find the best combination. As far up as possible should be correct, but should be and the real world are sometimes at odds.
When I was involved in racing the common statement for this situation was, horsepower costs money, how fast do you want to go?

 

[steelespike]

Re: Want more speed

I think a 5.8 230 should be able to make at least 40+ Is the prop in excellent shape?Is the speed by gps?Speedo is usually not very accurate,but not likely 10 mph off.
You could be experiencing excessive slip But I'm not informed enough to figure that.If the tach is accurate it would seem so. hwsiii may be along and he is slick,can figure it all out.Has a program to figure best prop.