Grady White Marlin

[shamblesumd]

Hey guys,

Looking for some feed back. Have a 2002 Grady White Marlin with a pair of F225's. looking to reprop the boat as I lost 6knots off the top end. (Which I can't figure out either) but I'm starting with the props. Currently running yamaha 15 1/4 X 17M SWS props which are in rough shape.

Looking for some numbers and feed back on what props you used, size, pitch and performance numbers would be great.

Thanks in advance!

 

[Bayhouse]

You should connect with Ken @ PropGods.com - he'll tell you everything you need to know. Props in "rough shape" are not good.

 

[Another Distraction]

If you lost 6 knots you have issues that props may mask but won't fix.

Did you test compression on the motors? Do both spin up to WOT throttle RPM's?

 

[seasick]

Hey guys,

Looking for some feed back. Have a 2002 Grady White Marlin with a pair of F225's. looking to reprop the boat as I lost 6knots off the top end. (Which I can't figure out either) but I'm starting with the props. Currently running yamaha 15 1/4 X 17M SWS props which are in rough shape.

Looking for some numbers and feed back on what props you used, size, pitch and performance numbers would be great.

Thanks in advance!

It would help to know if the loss of speed was gradual or all of a sudden. Although beat up props cab affect performance in different ways, there other things need to be checked before dumping a grand into a new set of props.
So..are the top end revs the same as they used to be or are they higher or lower ( by motor of course)?
Is the time to plane what it used to be?
Is the hull sitting lower in the water than it had been?
What does the hull look like; rough paint, crud, barnacles whatever.

If you have trim tabs, are they working correctly?
Have you removed the steering rods recently, replaced them or dismounted/remounted the motors?

If the WOT revs are lower, you might have a motor issue especially if the time to plane hasn't changed a lot. If the time to plane is slower, it could be props or loss of power.
If the wot revs seem higher than normal, it could be prop spin. Usually that will get worse over time.

If the hull i sitting lower and you haven't added a lot of weight, the hull or bilge is probably wet. See if the bow sits lower than you remember. The drain from the forward lockers to the bilge could be plugged.

Good luck

 

[shamblesumd]

Thanks for all the feedback.
To answer a few questions the WOT RPMS are the same on both engines before and after. Compression came back fine. However it does seem sluggish getting up on plane. Kind of like I'm dragging something. The bottom was just barrier coated.
I did have both exhausts fixed and the engine commes apart for that. So the boat did sit on dry dock for a few months after the bottom was painted. But it seemed to be fine afterwards. I had the voltage regulator replaced and filled up the tanks and that's when I noticed it. I did run a few more tanks of gas through it but no change.

 

[shamblesumd]

I also had the generator removed.

 

[seasick]

Thanks for all the feedback.
To answer a few questions the WOT RPMS are the same on both engines before and after. Compression came back fine. However it does seem sluggish getting up on plane. Kind of like I'm dragging something. The bottom was just barrier coated.
I did have both exhausts fixed and the engine commes apart for that. So the boat did sit on dry dock for a few months after the bottom was painted. But it seemed to be fine afterwards. I had the voltage regulator replaced and filled up the tanks and that's when I noticed it. I did run a few more tanks of gas through it but no change.

Some bottom paints need to get into the water relatively soon after painting. If not, they my 'seal over' and not provide anti-fouling protection. Eventually the bottom gets buildup of crud.

My other initial thought was that you might have prop slip. That could explain the slow to plane sluggish feeling but if a hub or hubs slip a lot, you will see the revs shoot up under power more than the speed increases.
I think you would notice the revs going up faster than usual though.
And of course, the props could be damaged as you originally mentioned but first I would check the condition of the bottom

 

[Another Distraction]

Exactly what rpm do you reach at wot?

I would try to get up on plane (and I know you can not) with one engine at a time to see the difference in power between port and starboard.

Also, do other f225 Marlins loose 6 knots at x rpms when full of fuel and gear? Those motors are not much over 207hp. Just asking, f225 guys go easy on me! ( I assume you mean at wot, not at cruise speed.)