Motor height - Merc 150 seapro

[Macdeep]

Your mounting height looks better than I imagined. I think that your height might be in the right range as-is. The other thing I noticed in your original pics is that you're running the motor trimmed very far down. I think that once you trim the motor a bit more neutral you'll see the anti-ventilation plate visible when running (considered ideal).

That looks like a basic aluminum prop. I think you will see better performance with a good quality stainless prop. Do you know the exact brand/model/specs of the prop you have now?

Ya, it is trimmed all the way under when running without the foil because otherwise I get porpoising if I release the trim angle to get more speed etc. If I release the trim angle on the outboard, I have to use the trim tabs to fight the porpoising which adds drag and is counter productive...

 

[Macdeep]

Your mounting height looks better than I imagined. I think that your height might be in the right range as-is. The other thing I noticed in your original pics is that you're running the motor trimmed very far down. I think that once you trim the motor a bit more neutral you'll see the anti-ventilation plate visible when running (considered ideal).

That looks like a basic aluminum prop. I think you will see better performance with a good quality stainless prop. Do you know the exact brand/model/specs of the prop you have now?

Yes, the model and specs of the prop are already posted above. Not interested in a SS prop. too $$. But would consider a 4 blade aluminum.

 

[Macdeep]

Do you have a 4-blade you can try? Adds lift at the stern. I do hope you get 90% there without the foil or 4-blade, and then they make it perfect.

Ya, I just have the one prop, but am in the market for a 4 blade ~14x19 or ~14x17. Already contacted NI props in Campbell, just waiting to see what they think for propping. But if there's a used one kicking about on the North half of VI, I'm back and forth between McNeill and Comox, Parksville and Qualicum regularly enough to make something work.

 

[SpringVelocity]

Ya, it is trimmed all the way under when running without the foil because otherwise I get porpoising if I release the trim angle to get more speed etc. If I release the trim angle on the outboard, I have to use the trim tabs to fight the porpoising which adds drag and is counter productive...

That isn't normal. Have you moved some of your weight forward. I am tending to think that extra 100 lbs is screwing you a bit.

On mine I moved my hali anchor...dr balls in the cuddy center in that cubby hole.

Also moved my batteries in back closer in towards centerline.

 

[SpringVelocity]

what is your leg gear ratio compared to his?

Mine 2.50:1

Seapro 1.92:1

 

[Pineapple Express]

Mine 2.50:1

Seapro 1.92:1

Nope. @Macdeep has posted a pic of his motor and the lower unit ratio is 2.08:1

 

[SpringVelocity]

I just grabbed if off website. Sorry didn't see that.

 

[Pineapple Express]

Ya, it is trimmed all the way under when running without the foil because otherwise I get porpoising if I release the trim angle to get more speed etc. If I release the trim angle on the outboard, I have to use the trim tabs to fight the porpoising which adds drag and is counter productive...

That is not normal. I think your mounting height may be close once you can trim the motor in a neutral position.

You've gotta address the weight issue. Shift weight forward. Look at lighter batteries. You can also experiment with ballast just to test how the boat responds to different centre of gravity.

Regarding the prop you're giving up a lot of performance by sticking with an aluminum prop. Mercury does make an aluminum 4-blade prop but the diameter is only 14" so you're giving up a lot of blade area with it being such a small diameter which defeats the purpose of going to a 4-blade prop.

 

[Max123]

Not to hijack, but I've been battling a similar issue in my boat. I've pretty much arrived at the conclusion I need to move my motor up to the top hole (its on the 3rd now). Here is a photo to compare - that is not the cav plate that is visible there, it's the one above it.

This is the 3rd prop and otherwise the best performer - a Solas 4 blade.
Honda 100hp on a Arima 17', that sits stern heavy due to main, kicker, fuel tank, and dual batteries all at the stern. Common downside to these hulls. I run with my front freshwater tank full for ballast, and keep all my rigger balls, anchor and other gear up in the cuddy.

@chille51 - you are minimum 1 - 2. Don't bother to try new props until you get the mounting height right because that will change your prop pitch again. When you are mounted too low, you are dragging the lower unit through the water. Once the drag is eliminated, you can typically gain 1-2" of pitch.

Its an easy change if you have access to the mounting bolts. When you have the boat on the trailer, lower the unit all the way down and shim blocks of lumber underneath till the skeg is supported. Then go to the front of the trailer and raise the jack so the hitch rises, and the back drops a bit. Once the skeg is fully in contact with the block, go back and look at the mounting bolts. You should have 4 bolts, and the upper mounts should be individually drilled holes, and the lower holes should be a slot (or the other way around). Take out the bolts two bolts in the holes, then loosen the two in slots - have a buddy hold the engine steady. Then go to the jack and crank it up - this will raise drop the stern of the boat so you can get in line with the upper mounting bolts. reinstall the top two bolts at desired height, tighten bottom two bolts. Done

 

[Macdeep]

That is not normal. I think your mounting height may be close once you can trim the motor in a neutral position.

You've gotta address the weight issue. Shift weight forward. Look at lighter batteries. You can also experiment with ballast just to test how the boat responds to different centre of gravity.

Regarding the prop you're giving up a lot of performance by sticking with an aluminum prop. Mercury does make an aluminum 4-blade prop but the diameter is only 14" so you're giving up a lot of blade area with it being such a small diameter which defeats the purpose of going to a 4-blade prop.

View attachment 125602

Roger - sounds like I should try to re-balance the weight distribution before moving the motor up any further or getting into a new prop. Though I do need a second prop any way. Was hoping to get a 4 blade to run as my main and keep this 3 blade as my spare.

Will get all my jigs and Hali lead in the cuddy as well as my spare cannon balls.

My concern is that any re-balancing now will be a net zero once I put the downriggers on, unless I add another 100 or so pounds in addition to rebalancing. Moving the batteries doesn't seem like a feasible idea - there's no where for them to go unless I do some re-modeling and substantial plywood and glass work, as well as rewiring which will be a costly project.

The quickest way is for me to make a substantial rebalance is to ditch my 9.9 kicker, but then I'd have to get down to a 17 pitch prop to be able to troll. With the 19p, idle is already pushing me at 2.5 knots. And to troll effectively, I'd probably want the fancy digital mercury smart craft controls which is a couple G$s installed... so ya, stuck between options that might not work and ones that definitely cost more than I'm prepared to spend.

I guess this is where I'm at before I shell out another grand lol

Step 1: move the transducer, keep the foil off for now.
Step 2: rebalance the weight as best I can, and re-test with down riggers etc so I'm at my final fishing weight and distribution.
Step 3: get the second prop that I'm going to get any way, but get one that offers good stern lift - ie. 4 blade in a decent diameter to max lift.

Then if none of that makes enough improvement

Step 4: move the motor up one last notch...

Has anyone seen ideas about putting a flexible rubber or plastic splash guard off the back? Would a 4-6" splash guard help? Or is that just a silly idea?