|
|
Rank: Newbie
Groups: Member
Joined: 7/10/2010
Posts: 6
Points: 18
Location: Sacramento, ca
|
I need some help. I recently purchased a 2001 Trophy 2352 which was not even close to being propped correctly. The engine was replaced in 2004 with a crate 350 MPI Mag. To get to the point, somewhere along the way, someone changed the gears in the Alpha 1 to altitude gears. I don't know the ratio, but I can't imagine there are too many choices. I've tried four different props and the best so far is a 14" X 22P 4 blade stainless but I can still pull right on past the redline at 30mph. She is a little slow getiing out of the hole for a boat that tops out at only 30mph. All of my boating is done at sealevel. Should I continue the search for the right prop with the current outdrive I have or should I change the gear ratio back to a 1.47 and reprop to keep the motor in the torque range which is was designed for? The boat is a bit heavy with a 100 gallon fuel cell, hard top and a four stroke kicker. My goal is tuna fishing which means a 50 mile ride to the fishing grounds. Cruising efficiency is very important. Currently, the best I can do is 13 GPH at 25mph which is taching 3800RPM. Any advice is greatly appreciated.
|
|
Rank: Administration
Groups: Member
Joined: 2/27/2007
Posts: 1,784
Points: 5,065
Location: Sarasota
|
You would think it would be a rocket out of the hole propped the way it is.
With your current 14 x 22 4 blade. what are the holeshot characteristics. Does the engine lug while its climbing on plane, or does it rev up to 3000+ and the boat catches up to it eventually?
Redline is 5000 rpm for that motor correct?
Do you have a lot of throttle left when you crack 5000 rpm?
What other props have you tried so far?
Right now, I'm leaning toward a 4 blade with more surface area. either the 15 1/4 x 22 Bravo I. or a Revolution 4.
|
|
Rank: Newbie
Groups: Member
Joined: 7/10/2010
Posts: 6
Points: 18
Location: Sacramento, ca
|
When accelerating from an idle to WOT, the rpm's climb to about 3700 and hold there until the boat gets on plane. The time to plane is directly related to the load I'm carrying. Sometimes when fishing, I may have four people on the boat so she struggles to even get on plane. Once the boat gets on plane, the boat is very responsive. I beleive the redline is somewhere around 5200.
Yes there is a bit of throttle left around the 5000RPM mark. The motor feels very strong at the upper end.
The boat came with two props and I have purchased two others. 15 1/2D X15P aluminum 3 blade- lots of power off the line but it hits 4800rpm and still does not have enough speed to get on plane. 14.25D X 21P aluminum 3 blade- labors to get on plane and you have to ease into the throttle or the prop will cavitate- good top end but I can still redline the motor. 14D X 20P aluminum 4 blade (Michigan)- Quick to get on plane but no top end; tops out at 25mph. Easy to over power and cavitate. 14D X 22P stainless 4 blade (Michigan Apollo) this is the prop I currently have which we've already discussed the symptoms.
So you think there is a possibility that I won't have to go back to stock gears?
Thanks,
Les
|
|
Rank: Administration
Groups: Member
Joined: 2/27/2007
Posts: 1,784
Points: 5,065
Location: Sarasota
|
You don't need to change the gearcase, your just slipping a lot. The props you've tried so far are fairly small in diameter and none of them have great traction.
First thing to check is for any through hull like a water pickup or anything like that. Or possibly a transducer that is inline with the prop.
It doesn't take much, and something like that can cause you to slip terribly.
If you don't see anything inline with the prop, then we'll just get you a prop that will have good traction.
The Revolution 4 would be my first choice. It has unbelievable traction.
assuming they went all the way to 1.94 gear ratio, your slip ratio is still 38% which is HUGE.
I'd start with a 21 pitch and we may need to drop down if it hooks up too much.
But go out and look at the boat and see if there is anything inline with the prop. Even something small that you don't think could cause any problem, let us know.
|
|
Rank: Newbie
Groups: Member
Joined: 7/10/2010
Posts: 6
Points: 18
Location: Sacramento, ca
|
Ken,
I’ll do my best at describing the underside boat layout. The keel is 12 feet long from the back of the boat before it starts to rise. The top of the prop sits 2” below the lowest point of the keel. The prop has a 14” diameter covering a 7” spread on each side of the keel. I think the rise from the keel upwards is 22 degrees. If you measure from the back of the keel towards the front of the boat, there are four hull penetrations all at 3’-6”. The two closest penetrations to the keel sit 6.25” from center. One is a transducer which stands proud 1/4” from the surface of the hull. The other is a head waste outlet which penetrates the hull by 3/8”. These two are definitely within the diameter of the prop but due to their low profile, I need your advice if they are a concern. The other two are 12” from the centerline of the keel so they do not sit within the diameter of the prop. They may still be a concern because one is a washdown pickup which penetrates the hull by a full 1” and the other is a head pickup which penetrates the hull by ¾”. If these penetrations are a culprit to the slippage, do they need to be relocated or just modified?
I appreciate your advice and I'm really looking forward to solving this. Thanks
|
|
Rank: Administration
Groups: Member
Joined: 2/27/2007
Posts: 1,784
Points: 5,065
Location: Sarasota
|
I'd probably give the Revolution 4 a run and see if it gets traction. It has MUCH better traction then any of the props you've tried.
I think it would hook up and run fine.
If not, then you can start relocating through hulls, but I don't think you'll have to.
Your motor actually sounds a little low, but at this point, I'd leave it where it is and see what happens.
|
|
Rank: Newbie
Groups: Member
Joined: 7/10/2010
Posts: 6
Points: 18
Location: Sacramento, ca
|
Ken,
Thanks for ordering the new prop; I can't wait to try it. I have a piece about the size of a quarter missing from my skeg. Its been this way since I got the boat and I probably should have told you about this earlier. The skeg is not bent in the slightest. The missing metal is in a very strange location. Its on the back of the skeg about four inches up from the bottom. The leading edge of the skeg has no damage so this never crossed my mind to tell you about it. I don't see where this would effect performance due to its location but I thought I should tell you about it anyways. The skeg has no other damage other than this missing piece of metal. What is your opinon here? Can the slightest imperfection cause problems? What do you think about skeg gaurds?
Thanks.
|
|
Rank: Administration
Groups: Member
Joined: 2/27/2007
Posts: 1,784
Points: 5,065
Location: Sarasota
|
I dont' think a missing chuck of the skeg would hurt anything inless it was bent off to the side causing a disturbance in the water.
I've seen a lot of people use the skeg guards that go over the existing skeg. You can also take the skeg to a prop shop and they can build metal back up on it and make it look new again.
But its not going to change anything on the prop issues.
|
|
Rank: Newbie
Groups: Member
Joined: 7/10/2010
Posts: 6
Points: 18
Location: Sacramento, ca
|
Ken,
When you get a minute can you shoot me a tracking number on the shipping?
Thanks,
Les
|
|
Rank: Administration
Groups: Member
Joined: 2/27/2007
Posts: 1,784
Points: 5,065
Location: Sarasota
|
Looks like your getting it on the 2nd.
I'm sending your tracking number via "PM"
|
|
Rank: Newbie
Groups: Member
Joined: 7/10/2010
Posts: 6
Points: 18
Location: Sacramento, ca
|
Ken,
You nailed it on the first try; what a difference! At 4500RPM she's traveling 41MPH. I verified this with two different GPS's and the pitot. The slip went from 38% down to around 9%. The slip is around 13% at 3800RPM but I imagine that should be acceptable. The boat jumps onto a plane faster than I ever could have imagined for a boat of this weight. You truely have lived up to your name.
Thanks for your help,
Les
|
|
Rank: Administration
Groups: Member
Joined: 2/27/2007
Posts: 1,784
Points: 5,065
Location: Sarasota
|
Great, glad it worked out.
|
|
|
Guest |
