I recently purchased a 1995 Grady white Explorer. I really powered the boat with a Yamaha 250 4 strokes. Does anyone know what size propeller the boat should have for optimal use??
Props
- Thread starter Gradyfisher01
- Start date
blindmullet
Well-Known Member
You said "strokes", as in plural... I assume you just mean one engine, though, correct?
Something's not jiving - it's not your prop. Your engine's max RPM is probably 6,000 - can you confirm?
I suspect you either have the engine mounted too low or you're not trimming the engine up enough as you go WOT.
Again, it's not the prop.
Last edited:
Are you sure about that 5,500? I just double checked on Yamaha's website and it definitely lists it at 6,000.
OK - do the test again, but keep trimming up. If the engine is mounted properly, you may get to the point where you reach the 6,000 (assuming, again) and still have trim and/or throttle left because you're actually able to go higher than 6,000. If that's the case, then a 17" is probably more like the correct prop. It's OK to go a bit over 6,000 for a short burst to check things out - sort of to try and figure out how many RPM's over Max you are to better figure out what prop to go with.
What RPM does your rev limiter kick in at?
OK - do the test again, but keep trimming up. If the engine is mounted properly, you may get to the point where you reach the 6,000 (assuming, again) and still have trim and/or throttle left because you're actually able to go higher than 6,000. If that's the case, then a 17" is probably more like the correct prop. It's OK to go a bit over 6,000 for a short burst to check things out - sort of to try and figure out how many RPM's over Max you are to better figure out what prop to go with.
What RPM does your rev limiter kick in at?
I tried 17-T Yesterday.that’s all the information about the prop, I don’t know the pitch. It performed about the same. Basically a mile or 2 per hour less.
blindmullet
Well-Known Member
That speed seems like it if off by a lot. I hit 44 with the original '93 225 and I'm a little above that with a 300 Zuke but need another prop as I'm only hitting 5500.
What hole on the motor are you using? Do you have bottom paint?
What hole on the motor are you using? Do you have bottom paint?
I think your right about The speed being way off. The max RPM on the engine is 6000 and I can only get the engine to rev up to 5500 RPM. And yes I have bottom paint. And the engine is new with 20 hours on it. I re-powered the boat and had a dealer install the engine. They use the same bolt holes as the original engine. So I know that the engine is mounted in the correct height.
OK, so you double checked and it's definitely a 6,000 max spec, right?
You mentioned you weren't trimming up. Have you corrected that? Meaning, you have to keep trimming up till speed no longer increases or the prop starts to ventilate (or you going to high over the max rpm).
Are you measuring speed with GPS or the dash gauge? Use GPS. Dash gauges (the pitot) can get clogged up and not be accurate.
From what's been posted, so far, it sounds like the issue is simply "user error"
Which is good, since it doesn't cost anything to fix it!
You mentioned you weren't trimming up. Have you corrected that? Meaning, you have to keep trimming up till speed no longer increases or the prop starts to ventilate (or you going to high over the max rpm).
Are you measuring speed with GPS or the dash gauge? Use GPS. Dash gauges (the pitot) can get clogged up and not be accurate.
From what's been posted, so far, it sounds like the issue is simply "user error"
Which is good, since it doesn't cost anything to fix it!The engine is supposed to max out at 6000. I have to trim up still but can’t try that till tomorrow
i am back at work till tomorrow. I will trim up and see what happens. I’ll keep you posted. I still think the speed is a touch slow. And you I am using GPS for speedOK, so you double checked and it's definitely a 6,000 max spec, right?
You mentioned you weren't trimming up. Have you corrected that? Meaning, you have to keep trimming up till speed no longer increases or the prop starts to ventilate (or you going to high over the max rpm).
Are you measuring speed with GPS or the dash gauge? Use GPS. Dash gauges (the pitot) can get clogged up and not be accurate.
From what's been posted, so far, it sounds like the issue is simply "user error"
Parthery
GreatGrady Captain
You really need to trim it up and see what happens. My guess is you will see 300-400 rpm and that will get you pretty close to the ideal wide open 6000 rpm.
As others have said, how are you measuring speed? GPS?
As others have said, how are you measuring speed? GPS?
OK - that's a very important piece to the puzzle. Nothing else is valid without doing that. Don't just trim up a little - do it the way I mentioned.
ScottyCee
Well-Known Member
- Joined
- Feb 11, 2020
- Messages
- 456
- Reaction score
- 86
- Points
- 28
- Location
- Samish Island, WA
- Model
- Sailfish
blindmullet
Well-Known Member
Trimming the engine isn't going to give you another 10MPH, but you may gain the RPMs. Are you 33kts or MPH? 33knts and a small adjustment will bring you into the 40mph range.