Prop and engine height questions

[1970rs]

Hello everyone, new to the forum and new to boating. I purchased a 1991 Ebbtide Dynatrak 200ss fish/ski with a 1994 Johnson Venom 200 2 stroke outboard on it.

I used it a few times last year to fish. This year I want to fine tune a few things. Did a tune up, changed lower unit oil and also replaced the water pump.

When i I got the boat, it came with two props. A 4 blade 13 1/8 x 25 and a 3 blade Raker 14 1/2 x 24. I decided to try the raker as I wanted to try and get more speed. Was only running in the mid 40’s on the 4 blade. Everyone says I should be close to 60 in this boat.

Took it out with the raker and it did not like it. Got the 5800-6000 rpm out of it, but no speed, still around 45 and it kept wanting to blow out allot. Couldn’t seem to get the trim to where it liked it either. Talked to a few prop gurus and they recommend a 22 raker. I found one but haven’t installed yet. Not sure why it was blowing out or cavitatiing.

At any rate, I assumed maybe the motor was too high. Checked it tonight and the distance from the lowest part of the hull at the V and the center of the prop is 5”. I’m reading 3.5” is a better start. I can raise the engine 1 1/2 “ or lower 3/4 with the current setup. Is it too low now?

Any comments or or suggestion on where to go next? Just trying to get the best performance and speed out of it.

 

[1970rs]

Here is a pic of current height.

 

[jimmbo]

RAKER is a good prop, and it can function well at higher engine heights. But as always your Mileage may vary. I used aa Raker on an 18ft Glastron Runabout, with the engine about 1 3/4" higher than the transom, the boat had what effectively was a setback which put the gearcase about a foot back from where it would normally from the transom, and the even when mounted solid on the transom, the AV Plate was an 1 1/2 above the bottom of the Hull.
A picture, taken level(not looking up or down), from the side at the Height of the Hull Bottom would give a more accurate visual as to the height of the AV plate. No wide Angle Lens(less than 50mm on a 35mm/full size sensor, or equivalent(35mm on crop sensor DSL), Phones cameras, are always too wide and that induces Distortion, unless positioned exactly, and I mean Exactly, Height wise, regarding tilting and panning.

 

[1970rs]

The photo was reference. I did an actual measurement to determine the 5” from prop center to the bottom of the v.

 

[Sea Rider]

I have personal issues with AV plate being set at a given fixed height which BTW in not fixed, each motor brand has its own height parameters which doesn't mean a thing. When combo is on plane will not know at which lower leg height will water flow pass by. Must pass between both horizontal plates, both heights achieves different combo performance. I like under the upper plate, other towards the AV plate, as with food, to each his own taste. The issue is that nobody test both settings in all kinds of water conditions.

If you're willing to experiment how to take the max out of said motor try this : Distribute deck weight evenly, when on plane trim motor to ride parallel to water level, visually check at which lower leg is flow passing by. Ideal would be to raise or lower the motor accordingly for water flow to skim right under the upper plate or the closest possible.

Once done, test both props on flat calm water cond and report achieved max wot rpm as loaded to check if motor runs at least rmiddle to max wot rpm range factory stated.

Happy Boating

 

[Faztbullet]

The dealer I worked for was the nations largest Dynatrak dealer and your motor height is set correctly as the hull is stepped. That hull is a 60+ MPH hull in bass mode but on the F/S models the console was moved 10" forward and addition of windshields. The makes COG way forward and boat has hard time lifting nose. Those with a 200hp was rigged with a 25P Renegade and you have to use the blow out ring. Also your props may need a tune up as the Renegade needs the double cup. This should put you in the high 40's to low 50's if motor is in decent shape.

 

[QBhoy]

Hi. That set up should be running close to or at 60 all day.
With regards to the height. It’s not so much in relevance to the prop, more the cav or anti vent plate to the lower hull you need to be setting up.
Generally high performance set ups should see the lower most plate on the outboard 1-3” (3 being the extreme) above the lower line of the hull. Anything lower and you will see serious chine walk on a fast hull and over a certain speed.

With the rpm you say....you should be charging on at way more than you are. Haven’t checked but I’ll bet your prop slip is ridiculous high at those numbers and that pitch.

 

[Faztbullet]

The hull is fine it the top deck that kills it. The FS model rarely ran over 55MPH. The windshield acts like a elevator and holds bow down at higher speeds. The Hydrasport F/S model you could remove windshield and pick up 2-3 MPH!!!!

 

[Faztbullet]

If you're willing to experiment how to take the max out of said motor try this : Distribute deck weight evenly, when on plane trim motor to ride parallel to water level, visually check at which lower leg is flow passing by. Ideal would be to raise or lower the motor accordingly for water flow to skim right under the upper plate or the closest possible.​

That works OK on rubber duck and motors below 30hp....below vids prove that theory wrong.
https://www.youtube.com/watch?v=15QnJHiwkBw
This one works well because of prop design.. designed for tips to surface
https://www.youtube.com/watch?v=Y9lZ2Ry7bYw

 

[QBhoy]

That works OK on rubber duck and motors below 30hp....below vids prove that theory wrong.
https://www.youtube.com/watch?v=15QnJHiwkBw
This one works well because of prop design.. designed for tips to surface
https://www.youtube.com/watch?v=Y9lZ2Ry7bYw

Totally agree faztbullet. Proper fast set ups run with the prop tips surfacing and the AV plate at least 1” or more above the line of the hull. Fact !

 

[Sea Rider]

We should let the OP test different transom/engine heights and find for himself at which hole height motor achieves the best water performance, that's best prop thrust, no aeration whatsoever on rough water cond and at tighr close turns at speed.

Don't know if current motor is an old or newer one, as both have different lower leg distances from upper to lower plate. The oldies usually 1.5 to 2.0 inches, the newer ones around 4.0 inches. Whatever transom height seated to works top with oldies, will not work same with newer motors due to plates heights differences.

Both posted videos doesn't say much at least to me, each combo was tested at near flat water cond, don't see any one of them performing at tight close turns or riding on rough water cond. Any prop will be considered to perform top if can hanlde all 3 situations somultaneously with 0 issues. If you guys like boating at straight boring water courses with motors raised or overly trimmed be my guests.

Happy Boating

 

[1970rs]

Faztbullet that is interesting. The original prop that was on the engine is a 4 blade 25p. I installed the raker 22 today and was able to get on the water. No blow outs with it and I was able to get 6000 rpm out of it. Only seen about 43mph. Although the lake was super rough today. I took a video running at speed with the engine trimmed for most rpm. Looks like it may be a little low as the cavitation plate is below the surface. Any thoughts?

 

[Faztbullet]

Don't know if current motor is an old or newer one, as both have different lower leg distances from upper to lower plate​

You have no idea of what your talking about. The Johnson/Evinrude 3 cylinder/V-4/V-6 plate distance hasn't changed in over 25 years, I was raised in late 2000 with the HP Lighting and Magnum series. The smaller motors and Tohatsu's maybe but not the one poster is asking about.

 

[Faztbullet]

Looks like it may be a little low as the cavitation plate is below the surface. Any thoughts? ​

Are you just fishing or do you ski/tube also? If you combo leave it be.

 

[1970rs]

Fish and tube a little. Trying to load the video, but not having much luck.

 

[1970rs]

Here is a picture I pulled for the video.

 

[Fed]

Try it without the speedo pitot, I recall a time when I picked up a very small Y shaped stick that caught itself between the bullet & the AV plate. This stick was tiny, less than 6" long and 3/16" diameter and it killed the thrust by at least 25%.
Lesson learnt, props don't like bubbles.

 

[Faztbullet]

I can see the top of cavitation plate as that's where it should be for combo use. That the 4 blade to a prop shop and tell em you a lil extra cup

 

[1970rs]

I looked today. The 4 blade is a shooter. I also was able to raise the engine a little. I was able to go 2 holes up which is about 1.5”. We will see what that does for it.

 

[Sea Rider]

You have no idea of what your talking about.

Yep you're 101% right, that's why stated not knowing if having the shorter or longer plates distance. If hasn't changed in over 25 years must be the old height style, motors you like playing with.

To me last posted pic shows a water milkshake going on out lower leg wake, the middle wake should be flat with no water disturbances, motor could be sitting to low or too high on transom, visually check at which lower leg height is water flow passing by at speed as a reference...

Happy Boating