Porpoise

[Dymonic]

Hello, new here and hope this helps me. I have an 18ft angler 180 and repowered it myself from a 90hp to a 150hp. The motor is 100 lbs heavier than my old 90hp and now it wont stop porpoising. I've filled the internal tank and moved all gear to the front besides the battery and oil tank.it get out of the hole great but no matter where I set the trim she still bounces. I've tried lowering the motor to the lowest on the transom and still the same result. Do I need a hydro foil? Trim tabs? Different prop? The prop I am running is a merc 14.5 ? 19p. Any help would be apreciated. Thanks

 

[fhhuber]

Prop too low will lift the nose. Need the anti-vent plate even with to a couple of inches ABOVE the lowest point of the transom.

You may need to shim the engine to allow the outboard to angle further "down". (low end forward / power head aft direction)

Fastest stable trim is from proposing, slowly use the down button of tilt/trim until the boat becomes smooth. a slight amount more down helps keep it from flipping nose over tail if you hit someone else's wake wrong.

 

[82rude]

Is this a glass boat?Whats the hp rating for her?Water logged?I had a problem boat years ago and nauticus smart tabs solved the bouncing right away .Upon closer inspection when i sent her to the dump i was carrying 800lbs of waterlogged foam!!!Weigh scales do not lie!

 

[Scott Danforth]

are you sure your not over powered. the 180 DC and 180 F are both rated at 140

they came with either a 90 or 115 yammy

however you should be using a stern lifting prop with your light boat

 

[Dymonic]

are you sure your not over powered. the 180 DC and 180 F are both rated at 140

they came with either a 90 or 115 yammy

however you should be using a stern lifting prop with your light boat

I do recall my 90 being shimmer. I'll look at it again though. I'm pretty sure I had to take the shim out for some reason. It could defiantly be raised and shimmed.

 

[Dymonic]

Is this a glass boat?Whats the hp rating for her?Water logged?I had a problem boat years ago and nauticus smart tabs solved the bouncing right away .Upon closer inspection when i sent her to the dump i was carrying 800lbs of waterlogged foam!!!Weigh scales do not lie!

Yes it is a glass center console and when I took off my old transducer I did notice water coming out of the transom. I think you a right about the water logged foam. That sucks. It would never dry would it?

 

[Dymonic]

are you sure your not over powered. the 180 DC and 180 F are both rated at 140

they came with either a 90 or 115 yammy

however you should be using a stern lifting prop with your light boat

Yep you are right it is over powered by 10hp but I don't think that should mater.

 

[Scott Danforth]

if you had water coming out of the transom, you probably have an extra 800# in the boat like 82rude mentioned. that water is rotting your stringers and transom.

in that case, the extra power doesnt matter, because if the transom is rotted, it will simply break off and sink the boat

 

[jimmbo]

That pic is a great way to explain why you don't back up with engine all the way down.

 

[Scott Danforth]

or what happens with a rotten transom in general. I like the obviously visible lack of wood in the transom with only wet mulch remaining

 

[Texasmark]

Prop too low will lift the nose. Need the anti-vent plate even with to a couple of inches ABOVE the lowest point of the transom.

You may need to shim the engine to allow the outboard to angle further "down". (low end forward / power head aft direction)

Fastest stable trim is from proposing, slowly use the down button of tilt/trim until the boat becomes smooth. a slight amount more down helps keep it from flipping nose over tail if you hit someone else's wake wrong.

I totally agree. Engine sitting too low. Get her up then set trim for sweet spot.

With the AV plate above the transom through wash, it is effectively out of the boat attitude loop whereas in it it has complete control and the problem as you have noticed is too much control. Once up above the through water, boat attitude is then controlled by thrust angle only. You get yer up and you'll be amazed at the difference in control.

 

[Sea Rider]

Post a pic of lower leg shot sideways exposing both horizontal plates to have a look..

Happy Boating

 

[Texasmark]

Hey Diamonic.......have you had your boat out yet with the upgrades????????