Rib Nose up???

[cheeseboat]

Can anyone help. I have a 4.2m rib with a mercury 60 four stroke. When in harbour at 6knts it sits nice and flat. Above this the nose sticks up ridiculously Like it’s trying to push under itself until it planes. Can anyone offer advice regarding engine position/trim/anything to improve this. If I try to pull a skier out the whole (heavy 95kg sods like me) the boat pitches nose up and struggles to get on the plane and acts more like a damn!

Engine height? Up or down? Would this help? All technical/practical advice appreciated.

[Iankristy]

Hydraulic or fixed trim?

[Jojosrib]

Originally Posted by cheeseboat

Can anyone help. I have a 4.2m rib with a mercury 60 four stroke. When in harbour at 6knts it sits nice and flat. Above this the nose sticks up ridiculously Like it’s trying to push under itself until it planes. Can anyone offer advice regarding engine position/trim/anything to improve this. If I try to pull a skier out the whole (heavy 95kg sods like me) the boat pitches nose up and struggles to get on the plane and acts more like a damn!

Engine height? Up or down? Would this help? All technical/practical advice appreciated.

I assume the engine isn’t too heavy......and the weight on the boat is at least central or preferably forward.....and the motor is trimmed in....if those basics are ok you may need to look at fitting some wedges for the engine mounts.... it’s also asking a lot for a 4.2 m boat to be comfortable in pulling out a95 kg skier..

[Last Tango]

Right leg length.....L, XL..? Prop set too deep ?.

[cheeseboat]

Originally Posted by Iankristy

Hydraulic or fixed trim?

Thanks for responding

It’s hydraulically trimmed. Trimmed full down.

[cheeseboat]

Originally Posted by Jojosrib

I assume the engine isn’t too heavy......and the weight on the boat is at least central or preferably forward.....and the motor is trimmed in....if those basics are ok you may need to look at fitting some wedges for the engine mounts.... it’s also asking a lot for a 4.2 m boat to be comfortable in pulling out a95 kg skier..

I think yes to those basics but need to check properly.

So would wedges to push the top of the engine back be worth a try?
I never need to trim up when planing.

[cheeseboat]

Originally Posted by cheeseboat

I think yes to those basics but need to check properly.

So would wedges to push the top of the engine back be worth a try?
I never need to trim up when planing.

And yes, I appreciate it’s asking a lot! I would loose weight but drinking and eating too much is for more inviting 🤣🤣🤣

[cheeseboat]

Originally Posted by Last Tango

Right leg length.....L, XL..? Prop set too deep ?.

The “ventilation” (I thinks that’s what it’s called) plate (the bottom flat fin) is roughly level wth the bottom of the transom.

[lakelandterrier]

The centre of gravity may be too far back I had same problem with my 4m Avon.with a 4stroke 40HP
On plane engine should be trimmed up c.halfway

I'd move what weight I can -batttery, fuel, etc. forward & see what effect that has.

Have you considered fitting Doelfins? - I found they made a huge difference.

Think about some ballast in bow as a further option

LT

[charliee]

very low powered engine to pull a 95Kg skier but it sounds like you have other issues at play to sort out first.

[cheeseboat]

Originally Posted by lakelandterrier

The centre of gravity may be too far back I had same problem with my 4m Avon.with a 4stroke 40HP
On plane engine should be trimmed up c.halfway

I'd move what weight I can -batttery, fuel, etc. forward & see what effect that has.

Have you considered fitting Doelfins? - I found they made a huge difference.

Think about some ballast in bow as a further option

LT

Thanks LT, really helpful. I’ll try all these tips.

[otilly]

I have the same problem with my little 330 rib, 15 hp. All I have to do is send the passenger forward and away it goes
So it's probably a weight problem.

[jeffstevens763@g]

not got water in the hull if thats the type of design, it should have a drain plug at the stern

[babbot1]

I would recommend "automatic" trim tabs, whatever brand you prefer. I have nauticus smarttabs on my rib and without them I can't get on plane with only me. It's too stern heavy.
They are spring loaded so they self retract when you get on plane. They have a chart on their website to fit the right spring strength.
You can also get a kit to manually retract them so they are not in the way for trailering. Sometimes I forget to put them down coming off the trailer and I instantly know whats wrong.

[Bremar]

I have a 4.2m zodiac pro with Yamaha 40hp 2 stroke. I weigh 85.3kg and the rib pulls me out with ease and that includes 3 adults on board. So not convinced there is a power issue. Like your rib when in harbour it rides very nose high and nose high before going on plane. In my case it’s definitely a weight distribution problem. Mine is back heavy and I bet yours with a 60hp 4 stroke will be too. Move bodies (weight) up front and this significantly reduces the nose up for me. Mine is a jockey seat with anchor spare fuel all up front. 40litres fuel and battery under seat. Still rear Heavy. Apart from adding permanent weight up front (or making people go up front (if they are on boar) until on the plane) the only other solutions/improvements I can see might be the use of the dolphin fins or the auto trim tabs mentioned by others and I haven’t tried either. I’m tempted tho. But your not alone. Good luck.
Bremar

[Poly]

Originally Posted by jeffstevens763@g

not got water in the hull if thats the type of design, it should have a drain plug at the stern

Definitely worth checking

[cheeseboat]

Originally Posted by Bremar

I have a 4.2m zodiac pro with Yamaha 40hp 2 stroke. I weigh 85.3kg and the rib pulls me out with ease and that includes 3 adults on board. So not convinced there is a power issue. Like your rib when in harbour it rides very nose high and nose high before going on plane. In my case it’s definitely a weight distribution problem. Mine is back heavy and I bet yours with a 60hp 4 stroke will be too. Move bodies (weight) up front and this significantly reduces the nose up for me. Mine is a jockey seat with anchor spare fuel all up front. 40litres fuel and battery under seat. Still rear Heavy. Apart from adding permanent weight up front (or making people go up front (if they are on boar) until on the plane) the only other solutions/improvements I can see might be the use of the dolphin fins or the auto trim tabs mentioned by others and I haven’t tried either. I’m tempted tho. But your not alone. Good luck.
Bremar

Thanks for replying. I understand and agree. The only thing on your side is the instant power of the 2 stroke. I’m going to try some weight shifting and also the wedges to see if I can use the engine to improve the stern lift. This should also give me some trim when I’m planing as I currently don’t have any need to. If that doesn’t work I’ll try the fins or tabs. I’ll report back so all who have offered help can read the results if your interested.
Thanks again
Cheeseboat.

[cheeseboat]

Originally Posted by babbot1

I would recommend "automatic" trim tabs, whatever brand you prefer. I have nauticus smarttabs on my rib and without them I can't get on plane with only me. It's too stern heavy.
They are spring loaded so they self retract when you get on plane. They have a chart on their website to fit the right spring strength.
You can also get a kit to manually retract them so they are not in the way for trailering. Sometimes I forget to put them down coming off the trailer and I instantly know whats wrong.

Thanks. I’ll try these if the wedges don’t do it.

[hesko]

Try a 4 blade prop that’s helped me. Now it just hops up onto the plane

[simonl]

Originally Posted by hesko

Try a 4 blade prop that’s helped me. Now it just hops up onto the plane

Same pitch?