Setup - Prop, speed, RPM etc

[Captain Obvious]

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[EuropeanAM]

Let's narrow down to a few focus points for now:

1. Do you have a Smartcraft Instrument? If not, you need one for accurate RPM's.

2. Have you had the engine checked to make sure that DEMAND LINEAR is reaching 100% at WOT position?

[Captain Obvious]

2

[MichaelJ3]

I just came off the lake. I calibrated the trim sensor, so it works now. I do have smartcraft instruments. I currently have the rpm set for digital output so it’s pretty accurate I think.

I have not had demand linear checked. I stopped by my local dealer this afternoon. They are not willing to look at the boat until late September because I didn’t buy my boat there and their customers come first. It’s not like I bought it across town. We lived 19 hours away and bought local. Needless to say I’m not terribly happy with that answer.

is there any other option for checking demand linear? I’ll spend money for software or whatever. I figure the first pass at the dealer will be at least $1k so it’s easy to consider spending that for some diagnostic equipment.

running tonight with trim at zero I got 5100 rpm. 28 mph. Trim tops out at 9.4 at WOT. With trim at 9.4 I could get 5260 rpm at 28 mph. Just like before, I can get more rpm but no more speed from trimming.

thanks for the help.

JP

There is probably more than 1 Merc dealer in the Lexington area. Maybe try a different one who is a bit more customer friendly.

[Captain Obvious]

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[Captain Obvious]

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[EuropeanAM]

Factory Warranty ended 8/03/2021.

Service Bulletins Outstanding:

SB 2018-010
SB 2019-001

[Captain Obvious]

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[EuropeanAM]

Service Bulletins are publications for Dealers and Boatbuilders/Partners, and are normally not published. Mercury does send letters notifying registered owners in many cases.

2018-010 is related to the potential of abrasion to the Start Relay wire.

2019-001 is related to replacement of the Shift Actuator Assembly

Both of these are relatively critical.

[Captain Obvious]

6

[EuropeanAM]

You are looking at a data item that is not adjustable, it is PCM controlled. PCM retains a reserve for the ASC features of the engine.

You may be able to "sweeten" the number slightly by improving propping or other setup parameters such as engine height or trim angle, boat loading, etc. Other than this, you can't change the figure.

[Captain Obvious]

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[Captain Obvious]

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[Captain Obvious]

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[leonreno]

You need to focus on props, and not just the stated spec of diameter and pitch but the actual model also. Here is a test review of your boat with a 200 hp Verado (I6 model) with a 14 3/4” x 16p Enertia prop, it would do 6200 rpms at 40.5 mph.

Also probably need to verify motor is at the right height and not to deep.



try this link, the direct YouTube links aren’t working:
https://www.boats.com/reviews/sun-tr...o-boat-review/
The video is on this page

[EuropeanAM]

Back on the lake this morning. Ran it with both the 13p 15.6" 3 blade and the 19P 13.5P 4 blade. Same old 28 mph and 70% throttle with the three blade. 4 blade got up to 95% throttle one time and then would peak 85% and then hold 80% on full throttle runs. Interestingly enough it would only turn 4500 with the 4 blade but ran exactly 28 mph. This tells me I'm getting basically the same HP out of the engine with either prop, one at 70% throttle and about 5400 rpm and one with 80% throttle and 4500 rpm both at 28mph.

I'll find a 15 and 16P prop to try in the next few days.

In the meantime, anyone want a big black anchor?

Captain Obvious- we're here in these forums to provide HELPFUL, PRODUCTIVE information and assistance.

Let's keep it to that (only).

Respectfully- your software setup is viewing the return sensor data based on PCM commands to an Electronic Throttle Control. This system is functioning exactly as designed by the manufacturer to achieve correct HP output and emissions.

Proper propeller selection on these requires monitoring of several data items and interpreting said data until the best prop selection is found.

[Captain Obvious]

Leonreno. Thank you, seriously. I appreciate another data point. 200hp, ~40 mph, 6200rpm.

[Captain Obvious]

Sharing an update to be helpful to anyone that comes across this. My issue was a plugged pitot in the lower unit. I have a separate GPS and never cared about the built in speedo working. I chased an "engine performance" problem for quite a while. In the end, I cleared a substantial clog in the pitot hole and picked up 500+ rpm and 6 mph on top end. Now at 34 mph. Now I still ignore the built in speedo, but the computer is way happier and giving me more timing on top end and it picks up RPM/speed. Max throttle blade opening still at 70% on top end. Demand linear checks at 100%. Lesson learned for me. The computer was holding back even though engine guardian said 100% available. Also seems it was holding back timing and not throttle blade position.

The plan is to buy a GPS antenna that will feed into the smartcraft system in hopes that I don't have to maintain the pitot hole in the lower unit. I keep the boat in the water so its a chore to pull it for this purpose as our marina doesn't have a ramp.

Now on to changing prop to try to get closer to the speed performance I'm looking for.

[EuropeanAM]

Just an FYI: There had to be something else involved. Many of these engines are running with NO pitot sensor or input, whatsoever- and performing perfectly well.

The plugged port could definitely affect Smartcraft Speed display, though.

[Captain Obvious]

Yes the smartcraft speed display had been reading wonky for a while.

As to something else involved, I hope not. Because nothing else changed. I'm tempted to put a piece of duct tape over the pitot and run it to see if there's a difference. Because if there's not, I'm going to be right back at 5200 rpm at WOT again at some point and not know why. We just got a new slip on Lake Cumberland which is 60,000+ acres. I'll need all the speed I can get down there.

I'm getting ready to do engine oil change, lower unit oil change, fuel filter, strainer, water pump, etc this weekend. I'll go run it afterward at the nearby river with/without tape over the pitot and see if it makes a difference. If it doesn't, I'll be back to square one but now with an intermittent problem which is even worse. I've had it out 3 times on the river with different props since the pitot was cleaned out and its been more powerful, reaching 5600-5800 each time which it wouldn't do before, its was about ~5,250 max before.

On the prop front, I'm finding that it has to have a large 15+" diameter prop to keep slip under control (~15%). I can get to 34 mph at 5800 rpm with the 15.6 Enertia 13P but can also get to 33mph with a smaller diameter 17P at about 5,600 rpm, slip is just way higher with the smaller diameter prop. Same with a smaller diameter 15P. I bought 3 stainless props off old mercruiser drives just to play with. Since I thought I had the performance issue solved, I was just playing with props before I put $800 into the proper one. At this point I think the 15" 15P Enertia is likely the right prop. If I keep the slip number close to what I'm seeing with the 13P I should be around 38mph and I'll be fine there. That would be a 10mph improvement from where I started looking into this.

I'll report back on the duct tape test. Either way, I want that answered before I haul it over an hour away and pull the trailer home. Once its at the marina, its waaaaay farther from the toolbox.