Turning 4850 at WOT on a Yamaha OX-66 225 hp. It's a 15 1/2 X 19 prop, Yamaha OE. Any recommendations for props? I have a Merc Stiletto in my garage someone loaned me to try, 14 1/2 X 17. But, I need the hub kit. Is this worth a shot?
Low RPM's at WOT Question
- Thread starter hotajax
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plymouthgrady
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yes. 4800 is way too low. You'll save the price of the hub kit in fuel alone.
14x17 (ish) seems to be the right prop for that engine depending on load.
14x17 (ish) seems to be the right prop for that engine depending on load.
Sounds like a lot of pitch for that motor but without the boat specifics, I can't be sure. If I had to guess, a 17 in pitch would be a better starting point. I might stay with the 15 1/2 diam. Find a good prop shop and ask for their recommendation. They should ask you about the boat and how you normally use it. If they don't, find another shop.
I have twin 0x-66 1990 yami 2-strokes on my GW 280 Marlin. I am also pushing low rpms. WOT @ only 5000 rpms. I have 14 1/2 x 19's (2) sets actually, one set as spares i keep on the boat.
I dont know much about the effects of the prop sizes except if you go smaller in dia you get quicker out of the hole but slower top end, or is it the pitch?
Dont mean to steal the original poster's focus but what would someone who knows reccomend I use for prop sizes and does anyone want to trade?
I am guessing 15 1/2 x 17? would that give me better fuel economy and reduce the loads on the engines allowing for higher rmps?
I always thought though, higher rpms meant more fuel.
Both sets of props are SS, one set polished the other painted black.
I would be willing trade a set with someone for the right sizes but I need both RH and LH.
I dont know much about the effects of the prop sizes except if you go smaller in dia you get quicker out of the hole but slower top end, or is it the pitch?
Dont mean to steal the original poster's focus but what would someone who knows reccomend I use for prop sizes and does anyone want to trade?
I am guessing 15 1/2 x 17? would that give me better fuel economy and reduce the loads on the engines allowing for higher rmps?
I always thought though, higher rpms meant more fuel.
Both sets of props are SS, one set polished the other painted black.
I would be willing trade a set with someone for the right sizes but I need both RH and LH.
Twisted,
For a reference point, a family member used to own a 89 Marlin with 1989 225 Evinrides. He was able to spin 15 x 17 ss props a tad over 6000 with a exceptionally smooth bottom. I did not notice from your post if you have 225s or 250s Yamahas on your boat. If you have the 225s I think your engine blocks are a little smaller hence your rpms with the same props would be a little lower. On the other hand if you have the 250s, your blocks are a little larger and you should be able to match or exceed 6000 rpm with the same props. Keep in mind I am talking about a lightly loaded boat in flat water, not what most of us typically encounter.
For a reference point, a family member used to own a 89 Marlin with 1989 225 Evinrides. He was able to spin 15 x 17 ss props a tad over 6000 with a exceptionally smooth bottom. I did not notice from your post if you have 225s or 250s Yamahas on your boat. If you have the 225s I think your engine blocks are a little smaller hence your rpms with the same props would be a little lower. On the other hand if you have the 250s, your blocks are a little larger and you should be able to match or exceed 6000 rpm with the same props. Keep in mind I am talking about a lightly loaded boat in flat water, not what most of us typically encounter.
hotajax said:
If it's really 15.5" in diameter, then I think that is a SWS II prop. Besides being 1/4-inch larger in diameter, it is a more aggressive prop.
I think a SWS 15.25 x 17" would be a lot better for you.
Really need more info re boat, bottom, mounting height, where trimmed at WOT, etc.
Brian
The engines are 250's, mounted on the second hole form the top (yamaha recommended) WOT is on the Harbor, still tide, clean bottom but painted and perhaps could use some stripping but I did sand and fill any dings / gouges in the bottom this past spring.
Finally, tests were done with motors tilted just below slippage and trimmed be be at optimum plane.
I am heading down to pick up the props this weekend and can tell what make they are. Boat had half fuel 150 gals out of the 300 gal capacity split between both tanks. Only myself on the boat, under 200lbs.
what do you think the difference would be between the 5.25 and 15.5 dia's? besides the 1/4" :lol:
Finally, tests were done with motors tilted just below slippage and trimmed be be at optimum plane.
I am heading down to pick up the props this weekend and can tell what make they are. Boat had half fuel 150 gals out of the 300 gal capacity split between both tanks. Only myself on the boat, under 200lbs.
what do you think the difference would be between the 5.25 and 15.5 dia's? besides the 1/4" :lol:
Twisted28 said:
My post above yours was intended for the OP.
As to your question directly above, the 1/4" won't make much difference. You are just overpropped, and the 19" pitch is probably too much. They are likely not Yamaha SWS props, so difficult to tell how much other factors may be affecting your RPMs at WOT, e.g. rake, cup, etc.
I think 19's are tough to push on any boat that is in the base power range.
Twisted, my marlin I'm running 17's with carbed 225's I can tach up to 6k which is running about 35knts. I cruise at 4200RPM at 25knts, 24gph, 1/2 fuel and water, 2 adults, 2 kids. jh
Twisted, my marlin I'm running 17's with carbed 225's I can tach up to 6k which is running about 35knts. I cruise at 4200RPM at 25knts, 24gph, 1/2 fuel and water, 2 adults, 2 kids. jh