Hey everyone. About two years ago when I had my motor in for some maintenance, it required the guys to take it out on the water. When they gave the boat back to me they told me that I had that wrong sized prop on there. Too small, or too little pitch. The RPM’s were too high, and the speed too low. Turning like 6,000 RPM for like 32 MPH. Seems a bit slow for the RPM. My WOT is about 6,400 RPM with about 32 - 34 MPH. I’m a bit confused by all the reading I’ve done as it seems different diameters and pitch give you different advantages and disadvantages. I’m wondering what you guys, with similar boats and motors, who run offshore, are using and why.
I have a SeaPro 220CC, with a 2001 250 Yamaha OX66 on the back.
The current prop has a mark on it, “17M” on the face of it, meaning inside the “round” part of the prop. So I’m assuming it has a pitch of 17. I’m wondering about recommendations for prop size. Any help or advice on how to start figuring this out would be wonderful. The boat is used mainly for offshore fishing. I’m not worried about getting out of the hole pulling skiers, or anything like that. I’m sure this will also help a great deal with my fuel consumption issues. I’m after better speed and a lower RPM, if that’s possible. Thanks.
Go to propgods.com ask Ken or do a search on there someone with the same boat/motor may have posted the same problem…he really helped mr improve my boat performance.
The first thing he will suggest is checking the engine height,i agree with that, amazing results from just moving mine up 1 hole…so far i have gained…3-4 mph and .3 to .5 in mileage and i still am trying different props…
Here’s the response I got from the other site. Ken said,
"Well, your current prop is slipping pretty badly, but I’m wondering if your tach may be reading high as well.
I would expect your rev limiter to kick in before 6400 RPM.
Your prop is a Yamaha prop. most likely the Salt Water Series. or SWS. should be 15 1/2 diameter X 17 pitch.
Your gear ratio is 1.81
6400 RPM at 32 MPH would be 44% slip, which is awful. It would feel like your tires are bald and spinning on a wet road.
For some reason, that prop just isn’t hooking up like it should.
It may have been repaired or reworked in the past, who knows.
1st thing to check would be to make sure there is no transducer or anything mounted on the boat in line with the propeller.
If not, I’d go with a 17 pitch Quicksilver Thunderbolt."
My question is, if I replace a 17 pitch prop, with another 17 pitch prop, won’t I be in the same boat, literally speaking?! LOL!!
Check and see if Skip is still in business at Skipps Propellar Shop on Cross County Rd in North Charleston. I have delt with him on repairs several times and have an uncle that was trying to find the right prop for his boat. Skip made recomendations and even let him take different props home to try. He was able to get the one that did the best job for his situation without having to buy a bunch of props.
Key West 19’6" CC 115hp Merc
14’ Fast Craft w/ 60hp Merc
It is my understanding about 10% slip is normal. To answer your question
About would another 17 pitch prop result in the same speed, the answer depends on the slip. I had twin 21 pitch props and I was getting about 32% slip, Mike at skips let me borrow a set of 21 pitch props with more cup and the boat run at the expected speed with about 9% slip.
I second working with Skips propeller , mike there knows his stuff.
I haven’t been to him in 3 or 4 years, but Mike did some pretty wild stuff on a couple of glitter boat for me. Man is allergic to stainless, but that is his passion. go figure?
He’s even let me try a few props as long as they came back in same condition.
You can follow the formula’s and come close, but the truth is in trying one out. I’ve had three Identical raker props out of the box and all were a bit different in performance. I’ve even carried a brass hammer with me and added “cup” to a prop myself and seen a substantial difference.
I was lucky in a lot of my prop selections to have several friends to borrow from and fine tune. After all that I used to keep two in the boat. one for me and a light load and one for the family and some possible skiing.
They used to have a variable pitch prop it was heavy, but started out with a low pitch and changed to a higher one. Wonder if they are still available.
What gut wrench said on engine height, too deep and a bunch of drag. Too high and possible blow out. Unless you have a jack plate that can be a time consuming adjustment. Best to find someone with a boat like yours and copy someone else’s labor.
Wonder if they are still available.