View Full Version : Prop and Fin Clearance?

05-01-2008, 06:47 AM
Does anyone know the clearance for prop and fins for the 07 OBV. I need to set my bunk heights on my hoist this weekend before it goes in the water. The boatmate trailers have a cut out which my hoist does not, so i certainly want to ensure proper clearance as to not damage them on.

would this be the draft depth in the specs ie 24". This is where i need the technical help from you engineers. :D I am just a numbers guy.


05-01-2008, 07:04 AM
Thats what I always thought draft was....
Kawasaki ZR1000A (http://www.cyclechaos.com/wiki/Kawasaki_ZR1000A)

05-01-2008, 08:36 AM
Yep, draft is when yer arse is gonna drag bottom. 24" sound bout right

05-01-2008, 09:01 PM
the best way to figure this is measure down from your trailer bunks
to the lowest point fin or drive shaft that will cross you horizontal section of your lift. also take into account if you have your lift tilted back slightly or level. i have been about 8 inches lower in the back to accomodate
our low water levels when they drop our levels. my shorestation bunks
are about 3/4 of an inch to low for my fins to clear if they drop our water levels we are kind of the red headed step children on the lower river here.


05-01-2008, 10:25 PM
Draft is one thing, the clearance for you lift is another. I set my bunks as absolutely low as possible due to low water in front of my place. I initially set the bottom of my bunks 12 inches above the bottom cross beam of my lift. I later after some inspection and so on was able to lower them to 9 inches. Your boat has a 24 inch draft which is how far down the 1st cross bar your fins will encounter will need to be + some extra below the surface of the water.

Hope this helps

05-01-2008, 11:01 PM
So 24 " is clearly too much. The lift will be in about 3.5 ft of water . I was nervous that i would have a water height problem at 2 ft over the cross beam. I don't have the boat yet but want to get the lift in ahead of time. Maybe I will just have to wait and measure the distance in two weeks.

sled wrote
Your boat has a 24 inch draft which is how far down the 1st cross bar your fins will encounter will need to be + some extra below the surface of the water.

I still dont get it :? ,
i guess i can try 12"-18" for height adjustment, we can get some decent wave action on th lake.


05-02-2008, 04:37 AM
if you're gonna float the boat onto and off of the bunks, you'll need to consider that said bunks are contacting the bottom of the boat, so from that position for clearance?

05-02-2008, 06:42 AM

Yes I get that .I just need to know that depth. If anyone could measure for me that would be appreciated ( clearance of the prop from the bottom of the boat). Or another measurement i could use is from the bunks on the trailer to the bottom of the cut out for the prop.

I wanted to finish my lift before i get the boat next week and the manual does not have this number.

Sled has his down to 9-12" , but i would hate to ding the fin or prop on my first trip from the launch :shock: that could get costly.

05-02-2008, 05:09 PM
I've got doubled-up 2x12s for my "bunks" on my lift - with a slight angle sawed out of them. These work fine.

24 inches is the amount of draft you need - but this is by no means close to how much room you need from where the bunks rest to the end of the prop/fins. Where the bunks would rest is under water from the draft line. I agree with sled that 9 inches should be enough, 12 inches is plenty.

Just be careful when the lake level drops - you are still losing however many inches thick your crossbeams are - meaning if your crossbeams are 3 inches thick, then you need 27 inches of water to clear them.

BTW (fine print) - I don't have to worry about my prop, only the fins...

05-03-2008, 07:35 AM
Scoot thanks as well as the rest of the board, I think I got it through my thick head. LOL

I think I finally got it I was thinking I need 24" inches "the draft" from the bottom of the cross beams to the bunks. But as I can see the arms for the bunks are not even 24" tall I will start with the 12 inches and go from there. and take in to consideration the cross beam height for the level of the water.


05-04-2008, 10:35 PM
OK, another dumb question...

I got the bunks and side guides on did not get it in he water, high winds and rain, yuk..

Anyhow, I set the bunks at about 26 " apart in the middle and the 38" (2x12) , then on my way home I saw a 2006 moomba ls on the side of the road of Keuka lake ( one of our members ironically) so I stopped to check it out and i noticed the bunks were about 4 feet apart on the trailer??

Question? Is how far (about 4ft) they need to be on the hoist?

sorry for the stupidity but f I had the boat, i would'nt have these questions, saturday can't come fast enough....

05-05-2008, 09:56 PM
jv -

Unfortunately, I don't live fulltime at my lake place so I can't measure my bunk width for you. I had to adjust these a few times myself. I'd say its best to match the trailer bunk width. The hull has built in grooves at this width to the guide the boat onto the trailer. Also, if too narrow, you could possibly hit the speedo or the water intake. In the end, I went about a half inch to an inch wider than my bunks to give a little play so I don't have to hit her just perfect...

05-06-2008, 06:27 AM

Thanks, Maybe my dealer has the answer where those grooves arebut maye i will just wait until she's home at the lake so i can do the final adjustments. Only so much you can do ahead of time for prep work. lol.


05-06-2008, 07:42 PM
I just set up my lift up this weekend for 20058 mobius ls. First I decided to us the same bunk width as the trailer which was 42". Then I measured the up from the ground to the bunk and did the same for the cross piece of the trailer. The height difference between the bunk and the cross piece height came to about 14". So I set my bunks at 15" to be safe. When I tried the boat on the lift everything was fine. I then lifted the boat up so that the cross piece was level with the lake to see how much clearance I have to the fins which was about 3" . Now I'm going to lower my bunks an 1" or so because I too face a low lake level at the dock. I hope this helps

05-06-2008, 09:52 PM
I also just set up my lift this weekend using almost the same procedure as Kipp. I used 42 inch bunk width for the entrance side of the lift (where the back of the boat sits), but I moved the front of the bunks closer together to help center the boat. I still have a little fine tuning to do, but this procedure worked great for me also...plenty of fin clearance.

05-07-2008, 06:19 AM
Is that 42 " from the inside measure of the bunks or the outside.? I will certainly give that a try this weekend.



05-07-2008, 08:48 PM
I think the 42" is to the inside of the bunk. As long as you are close you will be ok 42-44 inches. I also have to do some fine tuning, but I won't be in Michigan till memorial day to finish up.