New Boat w/ wrong prop??

[IGOTAIR]

Hello everyone, this is my first post but have searched the forum a ton as well as other websites and I believe the boat I purchased has the wrong prop.

Boat Information (as much as I know)
1. 1996 Celebrity 220 BR
2. 22' 1", 8' width NADA lists base weight at 3,800 but have not had boat weighed yet
3. 4- adults 35 gallons of fuel
4. Pleasure cruising (20MPH) pulling tubers, future wakeboarding
5. Moderate V- 18.5 degrees based on measuring diagram (http://forums.iboats.com/showthread.php?t=85275)
6. 1996 Mercruiser 7.4L Engine Serial Number OF 811841
7. 330HP (I believe based on what I can find) Ratio 1.5 as stamped on drive, serial number OF 813465
8. 4200-4600
9. N/A
10. Michigan Wheel Model# 033C34, 14 5/8" x 23 Stainless Steel
11. Current prop will run well outside factory rec. RPM (5100 without really trimming out the boat)

I was on relatively smooth water, 3 adults 2-children full tank of fuel when I realized RPM's at WOT, did not try to trim as I was over RPM's. I backed off the throttle as soon as I realized RPM's!! Speedo on boat does not work but using GPS I was about 46 or 47...This is my first boat and I am trying to learn as much as I can about boats and I obviously do not want to wreck the motor by having the wrong prop. My father in law states the boat plains nicely so I don't want to wreck that...

Any help is much appreciated. I have done a bunch of searching but it appears prop selection is somewhat of a grey area, depending on where you look. Please let me know if I need anything else, I tried to read all required info before posting.



Thank you in advance for your help.

 

[WAVENBYE2]

Re: New Boat w/ wrong prop??

Ok let me get this right, your running at 5,100 rpms at WOT?? and the recommended is 4200-4600? right

 

[IGOTAIR]

Re: New Boat w/ wrong prop??

Please re-read my post..

"when I realized RPM's at WOT, did not try to trim as I was over RPM's. I backed off the throttle as soon as I realized RPM's!!"

As mentioned in previous post, I just purchased this boat and this is the first time running at WOT, I was looking forward to see where I was going and when I looked back down to check RPM's they were over 5,000 (between 5,100 and 5,200) So NO I am not "running" at 5,100 RPM's, it was a one time occurance and I backed off immediatly, as stated in my previous post.

Because this is out of the range of the motor, I am assuming I have the wrong prop, (which is why I am posting)

Hope this clears up any of your confusion.

Thanks!

 

[WAVENBYE2]

Re: New Boat w/ wrong prop??

sounds like your prop is under pitched, and I asked you if the recommended is 4,100-4,600 rpms

 

[slydog75]

Re: New Boat w/ wrong prop??

Please re-read my post..

"when I realized RPM's at WOT, did not try to trim as I was over RPM's. I backed off the throttle as soon as I realized RPM's!!"

As mentioned in previous post, I just purchased this boat and this is the first time running at WOT, I was looking forward to see where I was going and when I looked back down to check RPM's they were over 5,000 (between 5,100 and 5,200) So NO I am not "running" at 5,100 RPM's, it was a one time occurance and I backed off immediatly, as stated in my previous post.

Because this is out of the range of the motor, I am assuming I have the wrong prop, (which is why I am posting)

Hope this clears up any of your confusion.

Thanks!

I think you took his post wrong. He was just trying to make sure he had the correct information, not chastising you for anything.

 

[WAVENBYE2]

Re: New Boat w/ wrong prop??

I was asking him for a reason, you prob know as well as I do you can lower your rpm's by changing the prop, If it was 4,200-4600 recommended and he was running at 5,100 sounded like the prop pitch is too low, I was only trying to understand exacly what it was he was wanting

 

[hwsiii]

Re: New Boat w/ wrong prop??

Igotair, I find questions with your numbers for gear ratio, speed and RPM. Because with the information I got from you I am showing a Power to weight number of 14# per horsepower and with that your prop slip should be very minimal, and what the numbers show is a prop slip of 39% and 95% of the heaviest cruisers show MUCH less prop slip than that. I imagine if you will check you will find that either the pitch is wrong on the prop, the gear ratio is wrong or your tach is wrong. My guess is either prop pitch or gear ratio.
I am NOT trying to get you upset, I am just saying it is hard to comprehend that much prop slip on a boat like yours. Even if your horsepower is more or less than you think it is that has nothing to do with prop slip, it only controls how fast you are able to go, not how much your prop is slipping, so you might want to check and see why. It is not impossible for this to happen but there is a major question somewhere and if I were you I would want to know where, beause it may be something that can be fixed and you might gain speed.


H

 

[steelespike]

Re: New Boat w/ wrong prop??

I think varifying the tach is accurate is the easiest way to start checking
for source of the prop slip figures.There is a fairly high occurence of tach error.

 

[hwsiii]

Re: New Boat w/ wrong prop??

I agree with you steele very much.


H

 

[IGOTAIR]

Re: New Boat w/ wrong prop??

Hey guys thanks for the feedback, as I stated before this is my first boat and I want to make sure I am doing everything right.

Wavenbye, sorry I took your first post as to say, "Hey you Idiot, you mean to tell me you know your boat is only good for 4200-4600 and you are running over 5K??? " I am on many other forums in different industries and I know how sometimes "new guys" can get trashed... once again sorry if I took it that way and you were just verify information.

I verified prop pitch with manufacture today and based on part number the pitch is right (I will however see if I can measure and determine

They (Michigan Wheel) recommended a 25pitch in order to reduce the RPM's within range.

I will very, prop pitch, tach and ratio as next steps before I change anything

Thanks a bunch!

Aaron

 

[IGOTAIR]

Re: New Boat w/ wrong prop??

Hey Guys...

Before taking the boat out this weekend and measuring with a dwell type tachometer I thought I would take a look at the connections tonight.

I had also read on some other forums where guys had fixed tachs by adjusting the pole setting on the back to a few other settings and then back to the proper setting. I thought I would give this a shot as I don't think it could hurt anything. I found that it was not set on the 8 Cyl mode, it was actually clocked off. This might explain why the tach was reading wrong...

I will test this weekend and find out. Thanks again for the help..

Aaron

 

[hwsiii]

Re: New Boat w/ wrong prop??

Please let us know the results.


H

 

[IGOTAIR]

Re: New Boat w/ wrong prop??

Well I re-adjusted the tach to the correct (8) setting and now I am getting just about 4K RPM's @ 47MPH trimming motor out .... 4-adults, full load fuel (35 gallons)....... Speed using GPS, averaged 2-direction...

I need to verify with the dwell/tach this week to determine if everything is correct.... If correct I am still thinking I have the wrong prop. Once again rec WOT is (4200-4600)

It continues I will keep you guys posted, thanks again for the help