Outboard height

[1959canadawood]

Outboard height with a step hull
See photo,I have a 2001 coral viper with a 150hp on it.
The engine seems to sit low in the water,should the outboard be raised
Thanks

 

[89retta]

It looks good to me

 

[ondarvr]

There is only one way to know, raise it and run it, then you'll know. The fin may allow you to raise it slightly higher than with out it.

 

[Sea Rider]

A pic says nothing, it all comes down to when boat is out of the hole and water flow passes at speed through lower leg. Check at speed on calm water cond pullig head over transom if there's back/over transom water splashes. If so raise OB a bit till disappear, if too much is raised, OB could achieve prop aeration issues at close turns at speed.

Happy Boating

 

[1959canadawood]

The reason I think it might be to low is
When I take off I need to have the outboard completely tilted down as low as it can then the nose comes up quickly then I need to trim it up as far as it will go up to get the most speed

 

[Sea Rider]

In reality, if weight is evenly distributed on deck, OB and prop are 101% healthy and OB sits at the "sweet transom height" no need to play excesively with trim, With neutral trim and OB sitting at 90?will plane near instantly if OB happens to run at its max wot rpm range as loaded.

The only possible way to look what's going on at back transom is having a visual look, installling a go pro camera at transom's side or flying at drone at back of lower leg., then will know what to do in order for OB to dial the sweet height.

Tomarrow will post a modified pic showing where must water flow pass by at speed, will improve your hole shot..

Happy Boating

 

[ondarvr]

In reality, if weight is evenly distributed on deck, OB and prop are 101% healthy and OB sits at the "sweet transom height" no need to play excesively with trim, With neutral trim and OB sitting at 90?will plane near instantly if OB happens to run at its max wot rpm range as loaded.


Happy Boating

,

​This is not even close to being true for best performance at speed. Some boats respond far better to trim adjustments, and the higher the performance of the combination (boat/motor), the more effect trim will have, both during hole shot and top speed. 90* might be adequate for mediocre performance on a lower performance boat, and many people do just set the trim in one place an forget about it, but this doesn't means it works well left in one position.

 

[Sea Rider]

You're seeing just one side of the coin. What about boats that hangs manual trim OB's would you say that you will need to modify trim when going out of the hole, once combo is on plane. Proper OB height & deck weight distribution are matters that very few considers for top boating, doesn't relly matter if iOB counts with a manual or electric trim. This isue could be discussed endlessly with pro and con answers as well. Each with their own theme..

Happy Boating

 

[ondarvr]

This is a 150hp motor on a hull with a transom step, it's not a 9.8 with manual trim on an inflatable.

 

[Sea Rider]

Happen to know those boats, If you preffer to play with trim and forget all about dialing proper OB height because it tires you too much, it's your problem. All boats needs to some extend some kind of fine tunning to better their water performance, doesn't matter boat type nor HP siting on transo, all floats and rides on water. Trim is just a small part of the equation.

BTW, those kind of answers will make OP to remain boating in Limbo Land forever.. and don't play clown making fun out with derogatory answers as well...

Happy Boating

 

[Sea Rider]

OK, let's provide a good technical solution to OP's boating problem, that's what this nice forum is all about..

Is your boat is something like this ? aft hull doesn't meet transom at 90? like standard boats ?



Happy Boating

 

[1959canadawood]

I did post a picture at the beginning

 

[Sea Rider]

You haven't answered my question about lower hull end shape, read again....

Happy Boating

 

[ondarvr]

Back to the real world.

​I've found it can be a little tricky with the step, well, at least frequently you can go higher than expected, looking at it doesn't normally give you a good answer.

​Raise the motor one hole and see how it works, you can test it with the fin on and off, I've found I can go one hole higher and get a couple more MPH with the fin on, but it's very specific to each boat/motor combo. Different props will allow different heights too.

​Most of the time when mounted new they go conservative and mount it lower than needed.

 

[Fed]

Back to the real world.

You made me snort my coffee. :lol:

 

[Faztbullet]

If you ski/tube height is perfect...if you ride/fish dump the fin and raise 1 hole. What you posted about trimmed all in to plane and trim out for max speed is 100% normal

 

[1959canadawood]

I'm going to try raising it and see want happens, were I live nobody stock a lift ring for lifting a 2001 mercury 150hp xr6
I thought I would make one does anyone know the size and thread that would screw into the top of the engine for lifting
Thanks

 

[Sea Rider]

Before venturing unbolting and moving OB up, need to determine by visual inspection where is water flow passing by through lower leg. With weight evenly distributed, trim OB well for hull to run parallel to water level at speed. If not it's a wild guess playing moving OB blindly, those OB's are quite heavy, without a lift or extra hands you're done...




Ideal max prop thrust is achieved when water flow at speed skims right under small upper water defector plate (dotted yellow line) and through sharp edge angle of attack , don't go over or under marked red X's. Report at which height was flow passing by ?



Just dial water flow at speed to skim as indicated, forget all about if middle water flow exiting middle hull is round, square, flat or whatever shape is it. Middle hull matters, side doesn't matter.

Happy Boating

 

[Texasmark]

Offset hull means higher engine height for best response. Reason why is that you want the AV plate as high as you can get it at WOT in the roughest water you run WOT in and still have the prop bite without blowing out. That is your highest speed. You are ok on height for a general answer. Question is where is the water passing the LU at WOT trimmed for the sweet spot. If passing over the AV plate come on up like you are suggestion. If even , ok sorta. If below definitely lift it.

Getting the AV plate higher will help the hole shot too as it cuts down on the tendency of the front of the AV plate to plow if too low.....that's the reason for your comment that you have to tuck all the way in.....that right there is telling me that you are too low. You have to tuck in to get the front of the AV plate to quit plowing.

Additionally on hole shot: From your comment about trimming all the way in to get a hole shot smells of too stern heavy with your what appears to be reasonable looking 20 degree(?) dead rise. The higher the dead rise the harder it is to lift the stern and get the bow down for the hole shot.

You have to get lots of power to the prop shaft to get the necessary thrust too. That means getting the rpms up fast. That to me translates to a ported prop like a Merc Laser II with the ports open all the way for a guess. Ports unload the blades of the prop by decreasing the density of the water flowing across them. Decreasing the load allows the engine to rev faster. Since HP drives the prop shaft which turns the prop which develops the thrust to move the boat, and HP = (rpms x torque)/5252 the faster you get the rpms up the faster you up the HP and spin the prop. Once up on plane the holes seal off and get out of the picture.

As you increase speed you normally trim out slowly because if you increase trim (push her out) too fast, you porpoise (somewhat on a deep V) until the boat speed catches up with the thrust angle whereby she settles down. Having to "jump" or "immediately" go from full tuck to full out is confusing to me. Never heard of such a thing being required. More pictures of your boat would help. You didn't identify it enough for me to look it up.

 

[ahicks]

Since we're sharing opinions....

It looks high already from where I'm sitting - but that's because I would take solid low and mid range performance in preference to getting the last mile per hour available from it.

The engine location is a compromise. You need to decide priorities to proceed in my opinion. The reason it requires all the messing around with trim is because it's mounted so high. If those needs are an issue, lower it! If the last mile an hour is the priority, raise it and see what happens!