At my wits end...

J

Jer_H

Cadet
Joined
Aug 5, 2010
Messages
16
Hi all,
Im seeking the advice of the prop gurus. I own a 2010 Sylvan Expedition with a 115-hp 4stroke. This makes for a very stern heavy ride. The boat is an aluminum semi deep v which i swear was NOT meant to hold the extra weight of a 4stroke. The boat wont stop porpoising.
Im currently running the Solas Amita 4blade 19" prop WOT is right about 6300rpm and 43mph GPS
Ive had the outboard raised to the 2nd highest setting and blow out on sharp turns or rough water. It cant go any higher.
Ive installed smart tabs but the boat is still porpoising. Even added 100lbs in weight plates to the bow. With the slightest bit of trim the porpoising starts.
Im Forced to plow water always trimmed down.
Im wondering if there is a ss 4-blade which could provide enough stern lift to resolve this prob once and for all

Suggestion? I keep reading about the merc rev4 but they dont seem to make one for my outboard
 
S

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: At my wits end...

Near as I can tell todays Merc. 2 stroke 115 and a 4 stroke weight difference is less than 30 lbs.
Take a 3 or 4ft straight edge and check for rocker in front of the transom.
 
QC

QC

Supreme Mariner
Joined
Mar 22, 2005
Messages
22,783
Re: At my wits end...

This sounds too severe to be solved with props. I'm with 'spike, check for rocker in the hull. Also consider higher rated actuators for the Smart Tabs, or the ultimate solution might be helm adjustable tabs. I had a seriously bad porpoise in one of my boats. Was never right, but helm adjustable tabs fixed it. Made it very usable despite the fact the weigh balance was still not right if you ask me.
 
Tail_Gunner

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: At my wits end...

Jer_H said:
Hi all,
Im seeking the advice of the prop gurus. I own a 2010 Sylvan Expedition with a 115-hp 4stroke. This makes for a very stern heavy ride. The boat is an aluminum semi deep v which i swear was NOT meant to hold the extra weight of a 4stroke. The boat wont stop porpoising.
Im currently running the Solas Amita 4blade 19" prop WOT is right about 6300rpm and 43mph GPS
Ive had the outboard raised to the 2nd highest setting and blow out on sharp turns or rough water. It cant go any higher.
Ive installed smart tabs but the boat is still porpoising. Even added 100lbs in weight plates to the bow. With the slightest bit of trim the porpoising starts.
Im Forced to plow water always trimmed down.
Im wondering if there is a ss 4-blade which could provide enough stern lift to resolve this prob once and for all

Suggestion? I keep reading about the merc rev4 but they dont seem to make one for my outboard
Click to expand...

Well two things are going on..maybe more. OK first is the four blade they are stern lifter's and you have lifted the engine up a bit much... aka blowing out . So what is going on is your skipping that shallow v hull across the pond and the porpiseing is the result..aka your hull cant handle that much speed or lift. Here post a pic of your engine leg straight down...lets see where your cav plate is relation to the keel Stay calm this should be easy..115 hp motor 43 gps is fast how long is the boat

Little side note.. i luv four blades on a hot boat..nothing quite like lift and speed but there is a price to pay. Any time i go for a long river run its back down to a 3 blade or i am going to to get a very sore back that day.
 
J

Jer_H

Cadet
Joined
Aug 5, 2010
Messages
16
Re: At my wits end...

Thanks for the replies. I'm going to have the boat out of the water this weekend so hopefully I can get some pics with the motor lowered. Prior to having it raised, I couldn't lower it all the way without driving the skeg into the ground, even with the trailer tongue dropped.

I have the 60lb actuators on the smart tabs and am also going to try and drop them another notch, and check for rocker in the hull. I will post my results.
 
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