Prop Selection - SR 19 HT Honda BF115D

[Fisherdv]

Just travel with the tide. You'll get the extra 2mph top speed you're looking for. 

[JDB]

Yeah, reduced performance characteristics... Insects/critters making a nest in the air intake passages, spark plug bad, fuel filter (including vst) clogged, fuel lines delaminated, air leak in fuel system, fuel pickup tube issue, anti-siphon valve broke....

[Tom C]

I'll give that a go tomorrow after coming back from fishing.

I don't think that's it since I was getting the same top speed before the transducer was installed.

Yes, good point, but still worth trying. Something is going on here. You're missing a ton of speed, and while the prop and motor height is not optimal, that can't be the whole problem.

[davidsea]

Everybody alway suggests the throttle cable. It's never the throttle cable on modern motors.

Who has performance reports for a 19HT? Can be any HP.

  Nanserbe's 19HT is likely a little heavier than mine, with a kicker, radar and fishing gear, but I have the full bulkhead , reefer, grill, etc.... it's 3050# with full fuel, 3800# on the trailer.  2018 Honda BF115, Honda/Solas HR Titan 3 - 14.75 X 16, with a bit of prop rework on the cupping.
  Perfect conditions - 42 MPH@6050 RPM, average 37-40mph, best econ. cruise 5.7-6 MPG@ 22-24 MPH.  See numbers below, on a 4-day cruise.


 

[Tom C]

So that's a pretty stark contrast, and it supports my estimate that Nanserbe's boat ought to do 38 MPH, not 28 MPH.

Something is really off with his boat motor.

[davidsea]

    Yeah, bottom paint can knock off some, but what else is helping to rob the MPH ????

[Fisherdv]

It's probably the 13 pitch prop, with large (15.5") diameter. Good power and thrust down low, not so good top end speed. Power down low is great for rough ocean conditions though, where there's more benefit vs top speed you'll rarely get to use.

Davidsea has a 16 pitch prop, and 14.75" diameter. I look at higher pitch as related to higher top end speed, BUT, the motor has to be able to turn that higher pitch prop up to proper (6000-6100 RPM) to be able to get that speed, which means the motor needs the power to get there, or a lighter loaded boat, smooth bottom, etc.

 If they make a 14x15p prop that fits his motor, or something in that size range, that may be the best he's gonna get on his particular boat, assuming there's no other issues going on.

Typical top speed for "most" ARIMAS is in the 28-32MPH range, most of the time, with a boat loaded up for fishing. My2c.

[Tom C]

It's probably the 13 pitch prop, with large (15.5") diameter. Good power and thrust down low, not so good top end speed. Power down low is great for rough ocean conditions though, where there's more benefit vs top speed you'll rarely get to use.

Davidsea has a 16 pitch prop, and 14.75" diameter. I look at higher pitch as related to higher top end speed, BUT, the motor has to be able to turn that higher pitch prop up to proper (6000-6100 RPM) to be able to get that speed, which means the motor needs the power to get there, or a lighter loaded boat, smooth bottom, etc.

 If they make a 14x15p prop that fits his motor, or something in that size range, that may be the best he's gonna get on his particular boat, assuming there's no other issues going on.

Typical top speed for "most" ARIMAS is in the 28-32MPH range, most of the time, with a boat loaded up for fishing. My2c.

No, none of that makes sense. We not talking about "most" Arimas, we're talking about a 19 with 115 HP. The larger gearcase has nothing, or little, to do with it.

Again, we are not talking about a marginal loss of speed, we are talking about a radical loss of speed.

[Fisherdv]

It's probably the 13 pitch prop, with large (15.5") diameter. Good power and thrust down low, not so good top end speed. Power down low is great for rough ocean conditions though, where there's more benefit vs top speed you'll rarely get to use.

Davidsea has a 16 pitch prop, and 14.75" diameter. I look at higher pitch as related to higher top end speed, BUT, the motor has to be able to turn that higher pitch prop up to proper (6000-6100 RPM) to be able to get that speed, which means the motor needs the power to get there, or a lighter loaded boat, smooth bottom, etc.

 If they make a 14x15p prop that fits his motor, or something in that size range, that may be the best he's gonna get on his particular boat, assuming there's no other issues going on.

Typical top speed for "most" ARIMAS is in the 28-32MPH range, most of the time, with a boat loaded up for fishing. My2c.

No, none of that makes sense. We not talking about "most" Arimas, we're talking about a 19 with 115 HP. The larger gearcase has nothing, or little, to do with it.

Again, we are not talking about a marginal loss of speed, we are talking about a radical loss of speed.

We are talking about a 19HT loaded for fishing with a 13p prop. It ain't winning no races.

[Tom C]

Yes, but the question is why it can't turn more than a 13" pitch prop.

You can't make a boat go faster simply by increasing the pitch. That won't create more power.

[Fisherdv]

Yes, but the question is why it can't turn more than a 13" pitch prop.

You can't make a boat go faster simply by increasing the pitch. That won't create more power.

See my above post again.

[Tom C]

Let me illustrate this another way.

Yes, more weight will slow a boat down. But for a 19' Arima with 115 HP than can go 38 MPH, you would have to add 2400 pounds to slow it down to only 28 MPH.

That's a lot of fishing gear.

[Fisherdv]

I agree he can probably do better. But even if everything else was perfect, turning a huge 15.5" diameter prop could be part of the problem. What is your opinion on a prop about 14" diameter with a 15 pitch? The smaller diameter may be able to wind it up enough for 15p.

[Tom C]

Propellers are not generic pieces of hardware described by just diameter and pitch. You have to consider the model of propeller, and its own characteristics.

There is nothing huge about a 15-1/2" diameter prop on a 19' Arima, and in fact, larger diameters are beneficial to this hull form.

Nanserbe's boat is new to him, so the fact it is fitted with the 13" pitch prop tells me the previous owner propped the boat to achieve appropriate WOT engine speed, but never addressed what is causing the loss of speed.

[Fisherdv]

Back to basic trouble shooting,
Check that the throttle cable is adjusted properly, and the throttle body butterfly fully opens.. Don't trust that the mechanic didn't get that perfect. Without verifying that, you will never get full throttle no matter what you do. Takes all of 5 minutes to check. See your service manual if unsure how to check it.

Next verify proper engine mounting height.

I know I already mentioned these two things already, but without starting with those two things and having those correct, it would never perform correctly.

[Tom C]

Yes, I agree, check everything. Could be the sum of many things, motor height among them.

A 19 Sea Chaser with an F225 pulled up outside my shop yesterday afternoon. I walked out to see how the motor was mounted. One hole up, which I would consider a bare minimum.

[Tom C]

Wait! now I'm looking at my own photo, I see they misdrilled the mounting holes; that motor is all the way down. Yet another motor that needs to go up...

[Fisherdv]

Agree, that motor looks too low.

If you get a chance to talk with the owner ask him about his top speed with that 225. That thing probably moves.

[Tom C]

Getting back to Nanserbe's boat, and it's low speed, we can look at it from another angle. If we use davidsea's boat as the comp, with goes 38 MPH with 115 HP, we can calculate that it would only take 62 HP for it to go 28 MPH.

That is a HUGE power loss.

[Mustard tiger]

I have a 2007 19 SR HT, 2024 Honda 115, 8hp Yamaha HT, dual batteries, trim tabs, 35 Gallons fuel, all fishing gear, 2 adults and one kid.
On the lake, light breeze small chop.  Definitely not a glass calm
5700RPM
3x15x15 Honda prop
33.7 mph max speed 

[Fisherdv]

Getting back to Nanserbe's boat, and it's low speed, we can look at it from another angle. If we use davidsea's boat as the comp, with goes 38 MPH with 115 HP, we can calculate that it would only take 62 HP for it to go 28 MPH.

That is a HUGE power loss.

No way a 19HT is going 28mph on 62HP. My 16SC barely goes 28mph with 60HP. 

[Tom C]

Oh, I bet it would, or close to it. My 17SR does 30 MPH with an F70

My point is that you cannot explain away a 10 MPH loss of speed by attributing it to rough bottom paint or low motor mounting height. I am increasingly puzzled by this one.

Once the simplest things are checked off, I'd have a mechanic verify it's firing on all four cylinders.

[Nanserbe]

Luckily for me, I'm pretty mechanically inclined.
I'll check the butterfly situation next, and I might even pull the plugs to ensure that they're all firing and good.
The engine only has 105hrs on it, but you never know. It absolutely throws you back in your seat if you jam on the throttle to get on step, so I feel like there's not a lack of power.

I did manage to get it to 6050rpm today with one other person on board, but this prop just REALLY REALLY likes to ventilate. After just a few seconds of trimming up it starts sucking air. It makes the RPMS increase, but not much in terms of speed.

My thoughts are that even with the A/V plate parrallel to the bottom of the transom the prop is partially out of the theoretical "water". Look at the prev photos with the tape measure. It seems like a lot to me but I'm not sure...

[Nanserbe]

Photos from earlier. Moving the transducer up helped a little with the spray but didn't change the overall speed. I used different trim tab bolts too without change.

[Nanserbe]

Short vid of the rear spraying attached.