Prop suggestions please

[atepoint2001]

I have a 2014 20 HP Mercury 4 stroke on a 16' Tracker Super Guide V16. I've only had it on the water twice so far and I can't seem to get it up on plane. The top speed I've gotten so far is 11 mph @ 4800 rpm. It has the stock mercury 3 blade aluminum prop (9.25 X 10"). WOT Range is 5400 - 6100 RPM. I am using it on a limited 20 HP lake. Maybe it's just not enough motor for the boat. Anyone have any suggestions on a prop to help me get some more speed? It also has a hydrofoil on it. I appreciate any help I can get. Thanks in advance, Todd.

 

[Sea Rider]

You can always maximize a prop if running under powered OB's. 4800 wot revs were achieved while lightly, medium or heavily loaded ? need that data. You are 1300 wot revs off, + 200 rpm gain per one less pitch decrease doesn't dial if lightly to medium loaded as could achieve somewhere between 300-500 + wot rpm with one less pitch.

Was weight evenly distributed on deck, was trim set to achieve OB remaining perpendicular (90 deg) while boat floats alone. Anticav plate & hydrofoil must ride parallel to water level when combo is on plane. If not, will achieve extra drag on lower leg which will slow down a bit.

Engine height is very important when maximizing props, do you have water splashes out or over transom at full plane and speed, prop aerates at close tight turns or at choppy water cond ? Which type of boating you like doing, fishing, cruising, speeding, family leisure?

Happy Boating

 

[atepoint2001]

Just the weight of the boat, myself (230 lbs), and an additional 75 lbs of gear. I would say weight was evenly distributed. Boat seems heavy though. Motor was tilted as tight to transom as possible due to bow running high out of water. No water splashing over transom. Boat is to be used mainly for fishing.

 

[steelespike]

What hp is the boat rated for? The boat is not planing so I think a 9" pitch may get it on plane.
Being stuck at 11 mph and 4800 I think that on plane will add more than 200 rpm per inch.
Remove the foil until we get an idea how it performs.
Don't worry about the mount holes.

 

[atepoint2001]

Rated up to 75 HP. 1,210 lbs dry weight.

 

[Sea Rider]

Could hull be waterlogged ? Move all weight towards bow if possible. Trim OB to sit at 90?on transon, remove doel fin if you like. Go for a wot tight close turn at speed on flat calm water cond, check if with prop aereation. Test is to determine if OB seats at its correct transom height.

A niner pitch will only pull wot revs tad more more than 4800, but not close to max top wot rpm. Better go for a 3 blade 8 pitch, should be closer to max wot revs. As this is not rocket science will need to be water tested with current load. At least will know how much wot revs you gained with a 2 pitch reduction, if still insufficient a 7 will make the trick. Check with prop dealer the posibility to test demo props before buying.

OB needs to run at near or full wot revs when in need to go full throtttle. Don't assume that will achieve a dragster speed, when running under powred OB's on heavier & larger boats better hole shot is preffered than aiming for max speed.

Check this vid, aim for water flow at speed to skim right under upper water deflector plate, that's the sweet OB/transom height for that 20 HP which is same rebadged Tohatsu. Move OB up or down to achieve that running cond. The OB seen on vid still needs to be lowered tag down for flow at speed to skims right under upper plate.

https://www.youtube.com/watch?v=oBeZjaA76VM


Happy Boating

 

[82rude]

Your grossly underpowered.You may never get that motor to plane out that boat.Having the motor tilted in all the way isn't helping either.Goodluck.

 

[Sea Rider]

You'll be surprised what a prop maximization, proper trim, correct OB height and deck balance can do for a under powered OB to perform nicely. If won't plane, at least will achieve a better fast displacement speed than before if you're not in a big hurry to reach your boating destination.

Happy Boating

 

[82rude]

I wish him well Sea Rider and if he,s on a smallish lake he will probably be ok but at the same time underpowered boats can be dangerous on larger bodies of water due to lack of power to get away from trouble (storms).IMHO that combo is way way under powered.

 

[atepoint2001]

I have water splashing over transom at full speed. What does that mean?

 

[Sea Rider]

Means that OB sits too low on transom, water flow that passes right under middle hull is banging over small water deflector plate, try adding wooden shims under OB start with 1/2 inch and test again. Need to balance deck weight evenly and trim OB at 90? for combo to ride parallel to water level when on plane. Test as suggested and report back. If back splashing over transon continues, need a slight taller shim than 1/2.

Happy Boating

 

[atepoint2001]

I installed a 9.25 X 8" prop and it put me right at 6100 RPM @ WOT but only gained me 1 MPH from 11 MPH to 12 MPH. I am still getting water splashing over the transom and still not on plane. I didn't raise the motor on the transom yet because I'm not sure if I want to drill a bunch more holes in the transom. I am trying to find a jack plate that will work with my Mercury F20ELPT Power Tilt with Steering (any suggestions on a brand/model)? There are clamps type bolts on the front side of the motor mount and they are 6" on center. Holes on back side of mount are 7 3/4" on center at the top and 7 1/2" on center at the bottom. There are 6 mounting holes (2 sets of 3) and a 3" slot on each side and the holes are spaced 2" to 12" down from where the mount wraps over the transom.

 

[atepoint2001]

Can I run it with just the clamps on the top of the mount tight or does there have to be bolts through the transom. Whoever mounted the motor initially put the bolt holes through the bottom hole on the mount so there is no upward adjustment without drilling new holes.

 

[Sea Rider]

If you add a jack plate will be offseting OB weight past transom, is it possible to post a pic showing transom to have an idea of what you currently have. If water splash is not canceled OB will not deliver it's full power as to go from there for a prop maximization as you're running a very under powered OB for that size boat. Horrible leg drag is what you have right now at back transom.

Never bolt my OB's to transom, just tight well clamps to transom, can place an individual rubber thin pad between clamp pad and transom for a better tight clamp adjustment. Does that boat have plates at both upper sides of transom, or it's plain alum, wooden or whatwever the boat is made of ?

Follow what's suggested on post # 6 to the letter and will be boating much happier than now.

Happy Boating

 

[atepoint2001]

No Title

 

[Sea Rider]

Some issues as pics are rather small to show full details.

Tracker shows a metal plate on transom, is it a external/internal sided single plate ? Your splash problem is : middle hull water flow at speed is banging on the upper round leg area *1. For that OB, water flow needs to skin right under small upper water deflector plate *2, for that will need to raise OB accordingly placing a wooden shim bracket's & transom width right under bracket.




The only way to check at which lower tail height is flow passing at speed is go for a wot spin on flat calm no wind water cond, with deck weight well balanced and trimmed at 90? for combo and doel fin to ride parallel to water level. Once there pull head out transom and check what's going on at lower leg. If combo and doel fin/anticav plate does not ride parallel to water level when on plane will achieve water drag there and slow down combo a bit.

How much can you rise OB for clamps to be well adjusted onto transom 1/2 inch ? if so, place a 1/2 inch wooden shim as suggested and go for another wot run and check if splash is gone, will only go when water flow skims right under greenish line *2.

This is the same issue boater used to have,

https://www.youtube.com/watch?v=oBeZjaA76VM

shimmed his OB as suggested and back splash is gone forever. To my particular taste he should have shimmed his OB less that 3/4 inch as for flow to skim right under upper plate. Your's is a rebagded same Tohatsu 20 OB.

Once there can go afterwords for a prop maximization. Report progress if wanting to go this way.

Happy Boating