Prop Ventilation Issue (air getting in prop causing spin out)

[Treedawg]

20 foot Sun Tracker Fishing Barge, 90hp Mercury four stroke CT, Stock Prop is Mercury Black Max 13(P)x16(D).

Ive had this boat 3 years now and have had Prop Ventilation (Slippage due to air getting into propeller) this occurs when I first engage the throttle if I dont do it nice and smooth and steady it will start to slip and I have to back off and repeat.. It will do this again once I hit about 4500 rpms if I have a 4 or 5 people with coolers and such..

With just 2 people in the boat and full of gas it will WOT at 5,500 RPMs and about 25 mph..

Which seems fine..

So this Spring I decided to change props to see if this would resolve the issue.. After talking with my mechanic we installed a 13(P)x 13.8(D) Nemesis Prop.. This prop is specifically made for pontoons and Mercury motors.. Got on the lake and I couldnt even get the boat up to enough speed to make a wake before the prop started Ventilation issues..

(slipping spinning do to air in the prop)

Ive put the stock prop back on and done as much research as possible..

I think the little V-Tab they put at the base of the fuel tank to protect the motor causes air be pushed down right into my prop causing all these issues.. Ive also heard that if I remove it the warranty could be voided..

Any ideas on the topic are much appreciated!

 

[racerone]

Motor is mounted too high.------Perhaps add an extension kit.

 

[Scott Danforth]

on pontoons, motor height is critical. too high, and you ventilate, too low and you plow/drag. of any boat that needs a hydraulic jack plate, its a pontoon. as you change your loading (by adding people or moving them around), you technically need to change the motor height.

 

[Treedawg]

I agree a hydrologic jack plate sounds like a super fix.. However I really don’t want to spend 2k fixing something that should have been designed better in the first place.. I hope Mercury / Tracker Boats has another fix unless they want to cover the cost!

Its already mounted as low as it will go on the normal plate.. Of course..

I have a picture of where the motor is mounted but I can’t get it to download here.. :/ I think I can load one but it looks giant on my phone.. Oh well I’ll give it a try..

Thanks for y’all’s input however.. It does make sense.. So frustrating.!!

 

[Treedawg]

 

[Treedawg]

https://share.icloud.com/photos/0Dnhohl3mt2GNGlgMoSHHJXvg

Think I got it! Lol

 

[Scott Danforth]

read the tutorial on uploading pics in the rules and guidelines forum. you have to reduce the size of your photo from multi gigabites down to about 400kb. most of us wont click on links

throw two coolers of beer in the back of the boat and the problem is solved until you drink the beer or move the coolers forward

all pontoons suffer this issue. its not a mercury issue as mercury has no idea what their motor is being used on. its not a tracker issue, as this is common with all pontoon boats.

its a rigging dealer issue if you bought the boat and the motor installed is not long enough to get the prop deep enough.

 

[Treedawg]

Thanks for the reply.. Yeah I bought it from bass pro, It was one of their recommended packages.. ..

However even if I put all the weight in the back of the boat it’s still happens with a fully loaded boat..

So you don’t think that V Tab part of the cause as well? Seems likely to me that little fella likely pushes a lot of air into the prop.. Seems it would be easier to remove the tab than drop the motor.. Cutting off the tab or lowering the motor should have the same results.. 1) Air shouldn’t get to the prop.. 2) the bad thing and why it’s there.. water could hammer the rear of the transom and cause other issues that would not be covered by the warranty because it was removed.. Geesh what a head ache ..!

 

[Treedawg]

Just figured out the problem.. “pretty sure anyway”.. The prop bore sleeve is missing.. Hopefully this $3 part gets me right.. I’ll let y’all know when I get it in place and test her out.! Thanks again for trying to help me out.. Much appreciated!

 

[racerone]

Funny.

 

[Treedawg]

About 10 hours of surfing the web trying to figure out my next step.. .. I’ll be floored if it doesn’t fix it though..!