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1990 MAV PLANNING ISSUE


Houston Maverick

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I have read a lot about the need for a Jack Plate. I have a 1990 with a 2019 Yamaha 115 SHO and a 2" Jack Plate. I have the jack plate on the lowest setting and no matter how I trim and tilt the motor I can't get on plane. I have seen Mav's with Jack Plates and I'm trying to understand what I am doing wrong. I can get up on plan after some time and speed. Meanwhile It feels like a tractor pull and then when I get the front down the boat will start bouncing. Please help. Any advice would be great. 

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Here are some photos. The front deck is recessed above the tank. I have trim tabs but the pump doesn't work so they are in the up position which is flat with the bottom of the boat. I have the jack plate attached to the lowest setting and motor mounted on the lowest hole for the plate to motor connection. What gets me is that when I throttle to go the back of the boat drops and its like a tractor pull.  

 

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4 hours ago, Houston Maverick said:

I have trim tabs but the pump doesn't work so they are in the up position which is flat with the bottom of the boat

100% your problem for sure.....the MA's are very sensitive to weight and tabs.

Forget the pump and just buy a set of Bennet Electrics...they are nearly plug and play.....I changed mine in about 2 hours.  The holes fit directly into the same holes and they are super fast.

dc

 

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I don't have this hull but it looks to me (Cant tell too well from the photo) like the engine could be mounted too high on transom. At least on my Hewes, (which also has a transom pocket) my anti-ventilation plate is about equal with the flat portion of the transom pocket and not the v of the hull. The boat really needs me to  trim the engine all the way down to come out onto plane or it'll porpoise like you mention. 

Hopefully someone with your hull can confirm where their anti vent plate is in reference to the transom to eliminate that as your possible problem. 

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On 11/24/2020 at 7:50 PM, Toeknee217 said:

I don't have this hull but it looks to me (Cant tell too well from the photo) like the engine could be mounted too high on transom. At least on my Hewes, (which also has a transom pocket) my anti-ventilation plate is about equal with the flat portion of the transom pocket and not the v of the hull. The boat really needs me to  trim the engine all the way down to come out onto plane or it'll porpoise like you mention. 

Hopefully someone with your hull can confirm where their anti vent plate is in reference to the transom to eliminate that as your possible problem. 

I agree.  Hard to tell from those pics but it does appear too high.  

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  • 1 month later...

Are you getting a lot of prop spin blow out when you hit the throttle? As others have said It appears the motor is at least a few inches too high. The anti cavitation plate should be at the same level as the hull's lowest level.  I have a 20ft  LT and it is set that way and I never have to use tabs to get up on a plane. I realized they are different hulls,but the concept is still the same.

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This is an old thread, so curious if the OP is still out there and if there is any update.   

Trim tabs are a bandaid here.   You shouldn't need them to simply get on plane.  Yes, they should help you get on plane flatter and faster, but if you need them to get on plane at all, something bigger needs to be addressed.

OP:   let us know if you are still dealing with this problem.   

 

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