Prop Recommendation

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Fandarr
    replied
    This is the tach, its only a few months old. I have check the dip switches and am 99% sure I have them set correctly. I also validated the RPMs with a handheld gauge/meter up to 2.5k RPM if I remember correctly and it they were the same. I want to test it at a higher RPM but need to get someone out there with me who can run the boat, I was just doing it in neutral.

    6Y5-8350T-83-00


    Leave a comment:


  • Parker Yacht
    replied
    Originally posted by Fandarr View Post
    I surely have wet foam that is a given. The boat is rated for 300 hp and many guys that run twin 150s on it see similar numbers as single 300s, atleast the guys over at classicmako. Originally they could have been bought with twins or a single from the factory. I am not looking for a speed boat like I said, just a good all around performer. I really liked the Thunderbolt Ken recommended and the Rev4 I borrowed from a friend, which is basically the Q4 Ken recommended but it was a different pitch. The rest I tried were just eh. I guess what suprised me and Ken even more was how bad the slip was and high the RPMs are. With both the Thunderbolt and the Rev4 the boat was actually pretty quick and responsive, much more than I expected. I just didn't expect to hit pretty much 6k RPM with any prop I tried and its been everything from a 17p to a 21p.
    What tachometer is in the bote?
    Engine has over-rev control at 6200, but really should be topping out around 5600.

    Leave a comment:


  • Fandarr
    replied
    I surely have wet foam that is a given. The boat is rated for 300 hp and many guys that run twin 150s on it see similar numbers as single 300s, atleast the guys over at classicmako. Originally they could have been bought with twins or a single from the factory. I am not looking for a speed boat like I said, just a good all around performer. I really liked the Thunderbolt Ken recommended and the Rev4 I borrowed from a friend, which is basically the Q4 Ken recommended but it was a different pitch. The rest I tried were just eh. I guess what suprised me and Ken even more was how bad the slip was and high the RPMs are. With both the Thunderbolt and the Rev4 the boat was actually pretty quick and responsive, much more than I expected. I just didn't expect to hit pretty much 6k RPM with any prop I tried and its been everything from a 17p to a 21p.
    Last edited by Fandarr; 10-20-2020, 08:55 PM.

    Leave a comment:


  • Parker Yacht
    replied
    If memory serves me correctly, the boat was never really designed for a single. It needed twins.
    We put a 300 Four Stroke o one up here, guy likes it, but it doesn't go out much.
    Heavy bote, especially if the foam is wet.

    Leave a comment:


  • Fandarr
    replied
    I am just trying to find a prop that will be a good all around prop. I am not super concerned with top end speed because I rarely run at WOT. Something that will give me a fast and efficient cruise is more important to me. It seems like each prop I try the RPMs and speed only vary only slightly even though many of the props have been very different from one another, and the slip numbers have been very high. The RPMs with almost every prop are right at the motors rev limiter. Ken has been helping trying to figure out why that may be and has a few theories that i am going to look into.

    Leave a comment:


  • Parker Yacht
    replied
    Originally posted by Fandarr View Post
    It's a 1976 Mako 25
    If you don't mind, without me reading the whole thread, what are you trying to accomplish?
    That year Mako and size is not known for much along the lines of speed and economy.

    Leave a comment:


  • Fandarr
    replied
    It's a 1976 Mako 25

    Leave a comment:


  • Parker Yacht
    replied
    What Make 25 is this? What year?

    Leave a comment:


  • Fandarr
    replied
    I still have it. The owner is not in a hurry to get it back. Won't the RPMs increase? Hey never know, I will give that a shot and see what happens. Probably won't get out until the weekend, work this week is busy and the sun sets so early these days.

    Leave a comment:


  • ken2
    replied
    If you still have the prop, I would absolutely hit the trim button and experiment to see what happens.

    Leave a comment:


  • Fandarr
    replied
    Hey Ken,

    So i was asking around and a friend of a friend had a 17p Thunderbolt that I borrowed this weekend. There is a lot to like about that prop. It did better in the slip department than anything I have tried yet. Cruise was a little slower than than the 19p rev4, which had the fastest of the ones i have tried. I really liked how responsive the thunderbolt was when you would hit the throttle. I have no idea why the slip numbers are still high, I guess when I pull the boat for the season in about a month or so I can take a look at the bottom and see if there is anything going on as you suspect. Here are the numbers I got this weekend, if anything the MPH might be 1 to 2 mph low. I didnt have a huge window of time to sneak out and it was pretty windy and tide was kicking today. I went in opposite directions and took the average of 2 runs to try and compensate. Again I did not trim up at all just to be consistent with the others.

    RPM - MPH - Slip
    2 - 8 - 56
    3 - 11 - 60 (stern really dropped down)
    3.5 - 15 - 53
    4 - 19 - 48
    4.5 - 27 - 34
    5 - 33 - 28
    5.5 - 37 - 26
    WOT (6) - 40 - 27

    It's amazing, like you said before everything is almost the same for each prop numbers wise. They all feel very different getting to those numbers but seem to end up the same. Is there anything else I can try to figure this out that you can think of? Seems like I may be in a holding pattern until I pull the boat and refresh my memory as to whats exactly is going on with the bottom. Being a new to me boat I am kicking myself for not taking a few pictures of it, oh well.

    Leave a comment:


  • ken2
    replied
    Well, having 30% ++ slip on a 25 ft boat without trimming the motor, banging the rev limiter with every prop you try, and all of them going within 1 MPH of each other regardless of style, or pitch is odd.
    Something is off.
    Your motor height description actually sounds low. would make a boat handle poorly, but normally wouldn't make the slip crazy high.
    Your not trimming the motor, which is definitely odd, but again, would not normally make your slip abnormally high.
    You say you've checked the tachometer, so we'll assume that is correct.
    You say you have used two different GPS devices, so I'll assume that is correct.

    I would attempt to trim the motor correctly with any of these props. See if your speed improves when you actually trim the motor correctly.

    That transducer can definitely cause issues. Its a pain to move it, but there is definitely a possibility that its causing issues.

    Leave a comment:


  • Fandarr
    replied
    This is the style of the abandoned thru hull transducer.

    Leave a comment:


  • Fandarr
    replied
    The motor is in the 3rd hole down from the top. When you put a straight edge from the keel the ventilation plate is about 1/4 to 3/8 above the keel. I have not looked at how the ventilation plate looks while the boat is underway yet. I have either been out by myself or with my kids. I am going to try and get out with a buddy this weekend so I can look and take some pictures.

    With most of those props it was hard to get the prop to ventilate. I was taking some really tight hard turns at high speeds that I would never due under normal circumstances and most never ventilated.

    The thru hull ducer is 3.5 ish inches in diameter and sticks down maybe 1/2 and inch.

    Leave a comment:


  • ken2
    replied
    The transducer I was most worried about was the one that was a through hull.
    but if its a really low profile, maybe its not the issue.

    And yes, even more strange that the slip is this bad with no trim, how high is the motor mounted?

    Leave a comment:

Working...
X