Listing to port side

schnurveyor · Feb 5, 2025

Recently bought 2006 Cobra R208 tunnel hull riverboat 25hp Mercury tiller 4 stroke. Rides level till reach 18 mph then starts listing to port. Listing is very severe at around 22 mph & no way I want to try reaching wide open throttle. Weight is distributed evenly with motor & battery on port side and myself & fuel tank on starboard side. Appears to be a 'hook' (don't know if that's the right term or not) added in the past at bottom of transom on each side of tunnel. Port side 'hook' measures 1 3/4" x 4 1/2" for 7.9 sq. in. surface area. Starboard side 'hook' measures 1/2" x 20" for 10 sq. in. surface area. Could this be the cause of the listing to port? Thank you for any thoughts.

Scott Danforth · Feb 5, 2025

the added bondo goobers on the bottom of the boat do not appear factory and look to be added.

Sprig · Feb 5, 2025

That is interesting. I’ve never seen a boat set up like that with OB on one side and having to balance it by putting weight on the other side.First thing that comes to mind to correct this is to try adjusting the trim tab. Also even though you think the weight distribution is even it may not be. Put some more weight on the starboard side and try it.
Also too late now but you should have driven the boat before buying it.

cyclops222 · Feb 5, 2025

Sadly Somebody butchered the bottom of the hull VERY BADLY.
Someone needs to remove the butchery blobs and return the hull to a normal shape.
You are right not to run faster.

southkogs · Feb 5, 2025

My first thought is that due to the offset of the outboard, the torque and weight are causing the list. I've never seen that setup; and frankly it looks like someone cutout 1/3 of the boat on the port sponson.

Are you able to center the outboard?

Mc Tool · Feb 5, 2025

I cannot for the life of me see why that WOULDNT list to port . Looks to me like the add ons are an attempt to fix the issue .
Dunno if its just the pic but that motor looks huge and I suspect that its way heavy . The way you describe the listing getting worse as speed increases suggest a weight distribution issue but you get to the point where you have to add so much ballast that the boat is overloaded.
Maybe you have discovered the reason the PO sold it .

rallyart · Feb 5, 2025

There are times where it is better to replace the problem rather than trying to fix it. If the boat feels unsafe, and is clearly not a normal hull, perhaps it is because its actually is unsafe and there are reasons a normal hull is different.

cyclops222 · Feb 5, 2025

The boat hull HAS A TUNNEL bottom in front of the prop. I enlarged that picture.
Boat is for a 400 pound guy ?

Grub54891 · Feb 5, 2025

I don’t blame the boat for wanting to tip over! I’ve never seen anything like that!

mr 88 · Feb 5, 2025

The hull appears to be very narrow , which in itself will list quicker and more severely than a wider hull . The port side of the hull has next to nothing for a planning surface compared to the starboard side . It will allow that side to dig in especially with the larger planning surface on the starboard side pushing up more/ harder, the faster you go . I'd be looking for a fixed trim tab , with some sort of turn buckle adjustments ,to put on that side . IMHO that " hook " on the port side , is completely wrong and is the first thing I remove then the other side That hook ,reverse scoop , will cause drag ,thus pulling or holding that side down . A trim tab will raise the stern with minimal drag .

DeepCMark58A · Feb 5, 2025

Only thing that kept me from commenting earlier I thought I was seeing things, who would design a boat like that? And Why?

schnurveyor · Feb 5, 2025

mr 88 said:
The hull appears to be very narrow , which in itself will list quicker and more severely than a wider hull . The port side of the hull has next to nothing for a planning surface compared to the starboard side . It will allow that side to dig in especially with the larger planning surface on the starboard side pushing up more/ harder, the faster you go . I'd be looking for a fixed trim tab , with some sort of turn buckle adjustments ,to put on that side . IMHO that " hook " on the port side , is completely wrong and is the first thing I remove then the other side That hook ,reverse scoop , will cause drag ,thus pulling or holding that side down . A trim tab will raise the stern with minimal drag .

Yes, narrow hull. 43" floor width x 20' 8" long. Very common trout fishing river boat dimensions. Older ones 36" wide with newer ones up to 60"+ running 9.9 to 40 hp motors. Also, the tunnel (good for jet lower unit) & offset motor aren't at all unusual on trout rivers. Made to run shallow, rocky rivers. Been around for years. I'm kind of old & slow witted so please bear with me. I'm of same opinion on the port 'hook'. Remove it & possibly replace with trim tab. Would you also remove the starboard 'hook'? Someone told me the 'hooks' were probably meant to help reduce bow rise on acceleration. Thank you to all on thoughts & comments.

mr 88 · Feb 5, 2025

I would try sanding off the lip of the hook so it looks like a continuation of the hulls bottom . Then after putting a tab on the port side , the wider the better , take it out and see how she rides . If still listing a bit , remove the rest of that section. Leaving it on will ,in a small way ,allow the boat to stay on plane at a slightly slower speed along with the getting on plane quicker , already mentioned above .
Depending on how handy you are , a local fab shop could make up a tab to your specs and design . Have to decide how it's attached to the hull , hinged -adjustable , or fixed which is a crapshoot that it is a perfect angle on the 1st try .

jimmbo · Feb 6, 2025

I have never seen a setup like that before
I would to see more Pictures of this Hull, from the Front, and with the Motor lifted.

cyclops222 · Feb 6, 2025

I would just sell the boat. Spend all the time & money on a normal boat.

Mc Tool · Feb 6, 2025

OK so its not unusual in your area. If its for putting the sneak on trout in small rocky streams was it actually designed to plane ? Im thinkin an electric motor would be better for sneaking up on Trout .... unless the "shallow rocky river " is also the local white water rafting hot spot

.
I get that a jet lower unit would line up with that tunnel and thusly be able to be mounted higher.
If your keen on the boat well........ I would get one of those bolt on cavitation plate foils and or a set of transom wedges and try and get a bit more lift off that motor ...... does it have power trim ?

southkogs · Feb 6, 2025

schnurveyor said:
Very common trout fishing river boat dimensions.

Been trout fishing for years and never seen anything like it (I'm used to seeing drift boats and flat bottom aluminums) ... BUT ... I did find a company that makes those tunnel hulls over in Arkansas. And they did have offset outboards on a couple. Roughly the same thing that you have. Very interesting setup.

I guess that makes the bondo stuff on the bottom of the hull my next suspect.

tphoyt · Feb 6, 2025

The bottom looks to be damaged. Maybe the foam is waterlogged.
Whats the max hp rating? What the beam?
I’m curious as I’ve never seen anything like it.

mr 88 · Feb 7, 2025

tphoyt said:
The bottom looks to be damaged. Maybe the foam is waterlogged.
Whats the max hp rating? What the beam?
I’m curious as I’ve never seen anything like it.

Might want to read all the responses before chiming in . Post # 12 gives you the beam along with the HP rating ( although that's not clear if it's for that particular hull or a larger one ) . Bottom and modifications have been discussed as well .

tphoyt · Feb 7, 2025

Ah I missed that

Listing to port side

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