Crestliner 20' pontoon nose dives.

[racerone]

Was asked about the reason a 20 ' Crestliner with 3 cylinder 35 HP nose dives.-----Apparently after 20 minutes or more of steady running it nose dives.------No water in pontoons.----Anybody ever heard of this ?

 

[HotTommy]

I've not heard of this, but I wonder if the bottom of the deck has been skinned. If so, I suppose it is possible it might fill with water over time. .... BTW, does trim have any effect?

 

[MRS]

How much weight you have on the front of the pontoon did you add something to the front?

 

[racerone]

Owner says they are just moving along steady state.-----Nobody on board moves.-----Suddenly it nose dives.------Never heard of it myself.------I imagine some folks on board might need new underwear after it happens.

 

[Scott Danforth]

did they hit something? did the motor quit running?

with no water in the logs, and running at a steady clip (nose up), and no-one moves to change weight, then it would be impossible to nosedive unless they hit something, or the motor suddenly dies throwing momentum forward.

 

[ahicks]

I think the owner may not be sensitive to the kind of details required for something like that to happen. In other words, we don't have the whole story here.....

If nothing is changing aboard the boat, then something else is changing, the size of the waves/wakes they are running into for instance.....

A boat floats or it doesn't. That's not going to change temporarily while underway.

 

[HotTommy]

I agree with the above comments. Something changed. Here's a hypothetical example. Driver trims motor up to push the stern down and the bow up. Everything is fine until a swell causes the raised prop to momentarily reach the surface and cavitate. Downward thrust on the stern is lost and the bow drops. ..... Yeah, we need more info.

 

[racerone]

I was hoping someone experienced this with a Crestliner pontoon.-----No further suggestion please.

 

[Scott Danforth]

Racer, suggest you go for a ride to witness first hand.

 

[Scott Danforth]

racerone reading similar posts on iBoats and other forums about nose-diving pontoons.

nose down attitude and bow heavy appear to be the prevailing underlying causes. waves and swells are what is the triggering event.

https://forums.iboats.com/forum/gen...0768-pontoon-boat-did-a-nose-dive-while-going

https://forums.iboats.com/forum/gen...s/579911-new-pontoon-owner-did-it-almost-sink

https://forums.iboats.com/forum/gen...pontoon-boat-nose-dives-in-semi-rough-weather

http://www.pontoonforums.com/viewtopic.php?t=22961

 

[Starcraft5834]

did they hit something? did the motor quit running?

with no water in the logs, and running at a steady clip (nose up), and no-one moves to change weight, then it would be impossible to nosedive unless they hit something, or the motor suddenly dies throwing momentum forward.

Agree with Scott.... physics being what it is........ this cant happen.. forward thrust of any marine vessel pushes the nose up... even water in the logs would go backwards... driving into a breaking wave?

 

[cc350]

Need to trim the motor up, If it's in the lowest position it will push the bow down.