Hinge Pin Angle - Progressive Mechanical "Power Trim"

[Brian Sorgente]

Hi guys,

I recently got into running outboards and I thought this might be a cool topic... Like everyone else, I’m always trying to learn how, when, or why to make adjustments to improve the boats handling / speed etc... Recently I've been thinking about adjusting the hinge pin angle to set the attitude of the boat when cornering verse on the straight.

As I’m sure many know, with the OS style lower, you’re able to adjust the prop shaft angle separately from the hinge pin angle. You can do this by shimming the hinge plate on the transom to a desired angle then set the prop shaft to its desired angle using the trim adjustment screws. Depending on the direction you angle the pin, this will alter the angle of the prop shaft as the lower unit is turned.

I've also seen others tip the pin side to side to get the same effect. I assume this is a much more aggressive way to go about getting the same result.

I was hoping to start a general discussion of why someone might angle the pin backward/ forward, side to side, or even both. Aside from trial and error are there any clues that might tell you to do one instead of the other? How much of an effect should you expect when making these adjustments?

Brian

 

[dion smith]

My gas ob leg works like this(camber leg) and it works well- rolls the hull into the turn a bit and allows a faster turn

 

[Travis Benjamin]

Great post I'm all ears.

 

[kesso2118]

I asked the question about the effect of Pin Angle changes a while back and found some of the answers seemed to to contradict each other, so I followed a valuable piece of advice I was given and tried it for myself

The problem I was trying to correct was what I called an "understeer". The boat was fine at slower speeds but at higher speeds the boat was drifting at the beginning of the turn. This was accentuated in glassy water, however, If there was some wind chop or even just a fine wind ripple on the water the boat would turn better. I tried a number of changes with props, weights, trim angle and prop height with varying success.

The most effective change was when I placed a .036" washer on each of the two lower mounting bolts between the bottom of the OS Hinge Pin Plate and the transom. The immediate effect was the nose of the boat was lowered as soon as any rudder was applied and this allowed the boat to begin to track much tighter into and around the turns

Another effect was any slight rudder adjustment while running down the straight tended to kill some speed because of the extra pressure on the nose of the boat. I relaxed some of the negative trim I had been using and it "softened" the effect, however, the most important thing I learned to minimise this effect, was to make sure that once the boat completed the turn I pointed it in the right direction and then just let it run. It's very satisfying watching it accelerating out of the turn and once you release the rudder you see the nose begin to come up and it starts to boogie B)

 

[Wayne Johnstone]

Is that the set up you had on Ronald last time we were at the pond?

 

[kesso2118]

No Wayne, Ronald has always been a sweet turning boat, however, with the set up you saw running last time at the pond it was getting a little bit light at the beginning of the turn and when running over another boat's wake it was slipping sideways a little bit

 

[ozbryan]

In which direction Greg?

 

[kesso2118]

That's interesting Greg, I assume that would make the boat run heavier on the right hand sponson? Do you feel that this allows the boat to get a better bite from the inside edge of the right hand sponson through the turn?

 

[ozbryan]

Interesting!

 

[kesso2118]

How did you find it running in a straight line, did it lean to the right hand side??

 

[kesso2118]

Just wondering if anybody has any other comments to add to this thread about the effects of steering pin angle changes?

I thought this was a good question when the thread was started but it seems to have had little response from people who are experienced Outboard Tunnel Tuners so I thought I would try and get it back on the "front page".

 

[Brian Sorgente]

Greg- Our of curiosity why delete your posts? I guess I'm still setup to get notifications on this and was surprised to see some action.

Anyway, maybe there are some others that could get this conversation going again.

At the end of last year I tried to get a feel for what this adjustment would do by really throwing a lot of angle at it. I pretty much left with more questions than answers. I shimmed the top of the hinge plate probably 3/8" or more (basically as much as I could get in without worry of hurting the transom) hoping to lift the nose in the corner. I figured shimming it that much I would see something pretty noticeable but it didn't really do much. Thinking back on it now I think it may have just been the boat I was testing at the time...

I did notice a difference this past summer playing with tipping the hinge pin from side to side to tighten the boat up in the corner.

Brian

 

[Brian Sorgente]

Well good luck... Lol you only have about 2700...

 

[RonShaw]

Whats up Greg? You add a lot to the topics on IW. Everything ok?

 

[dave roach]

Delete

 

[RonShaw]

Whats up Greg? You add a lot to the topics on IW. Everything ok?

Im done here

Oh no. What the heck? PM me!!!

 

[Carl Van Houten]

It does affect the trim going into the turns. It doesn't help every boat. It depends on what your boat is needing. If your boat already has the tendency to tighten up through the turns, this is something you would want to stay away from. I have used the technique for years but I only do it when needed. It just depends on the overall nature of the design. The Lynx has made use of this feature for fifteen years or more.

-Carl

 

[Tim_Duggan]

Well said Carl, and a question if I may? What is a good way to overcome the " If your boat already has the tendency to tighten up through the turns" ?

Tim

 

[Carl Van Houten]

That is where you will need to do a lot of testing. To point you in the right direction, if the steering is a bit tight I would start by looking at the dead-rise in your sponson bottoms. Although there are many other things that come into play when carving out the perfect turn, the dead-rise would be the first thing to start playing with in order to get your model closer to the desired amount of bite. You will see a one degree change so don't over do it. It usually requires a combination of features that work together to carry the model from initial set through to the exit of the turn.

-Carl

 

[Steve P]

Carl

Can you give an explanation or drawing of what dead-rise is?......I have heard this term used before just want to make sure I understand it.

Steve