Outboard tuning/ prop set-up

[bushwacker]

So I ended up pulling the trigger and re-powering my boat. The motor was slightly used with just 16.5 hours on it. It’s a 2018 Mercury 150 four stroke. It came with a prop which is a stainless power tech with a 19pitch and 14 1/2” diameter. I am pretty slow out of the hole and seems to struggle to get on plane with low rpms coming up. Boat is a 1995 hydrasport 21skiff it is 21.8’ and seems pretty heavy. Once on plan I am topping out at 4800 rpm’s and 37-38mph and the motor is rated at 5000-5800 WOT. I do have a jack plate and feel the motor is too low as I can’t trim out at all without the bow bouncing. Boat has self adjusting trim tabs as well with 80lb acurators. What are y’all a thoughts and who around the lake is good with setting up this. Thanks for all the help.

[johnr]

Interesting prop you have there. I am running a 14.5 x 21 on a 90, spinning it at 6200rpm and getting 38-42 depending on load. Roughly 2500lbs as it sits now. I say this because I would expect a 150 to have a larger diameter and maybe 23p as a good starting point. The fact that you arent over revving does indeed make me think you're set to low, but thats hard to know without seeing it. Also, powertechs are usually one of the better performing props.

My boat was slow when I got it. It was only turning 5500rpm and should have been around 6200. I raised my engine several inches and it was a night and day difference in all performance aspects. Much better across the board.

With a jackplate, I'd think you would have no problem tuning it with the current prop. Beyond raising it, swapping props is the only other real tuning to be done. There can be a huge difference in props, but you just never know until you test one.

Last spring I bought a brand new yamaha stainless prop and promptly destroyed it. I replaced it with an aluminum prop that I had rebuilt, and that rebuilt prop is a good 3mph faster than any of the new props ive had on it. So you never know.

[bushwacker]

This is just the prop that came with it and the boat the motor was on was an 18' CC. I spoke with Ken Reeves from propgods and Powertech they both suggested running a 4 blade in a 15" or 16" pitch. I think the motor needs to come up some but looking at it only a couple inches at most. I think I am going to try the 4 blade 16 pitch. My last motor had a 21 on it when I got it, which I think the owner put on and keep the lower pitch when he sold it to me. I was having a lot of the same issues. I switched it to a 17 pitch and gained my RPM's back and 3-4 mph on top. Boat is pretty heavy with all the gear and 35 gallon bait tank.

[bushwacker]

Ok so I tried the 4 blade and it was not much better maybe came up a little faster but still real sluggish and I lost 3-4 mph on the top end and still only made 4800rpm's. So back to Anglers Choice the boat went. I spoke with a couple mechanics around the lake and none really liked the idea of a 4 blade. So the 4 blade is off and going back for a refund. Angles took a 15p and a 17p 3 blade to philpott for a lake test. The results were much better. unloaded the with the 15P Anglers was seeing 6000rpm's and 38-39 mph and had a great hole shot.The 17P was making 5550rpm's and was a little longer to plane say 4-5 seconds, but was reaching 43mph. They left the 17p on and told me to try it out this past weekend to see how it would do loaded down tournament weight. My first test was Thursday eve unloadedish with an empty bait tank and just me and my son on the boat. The boat came up to plane pretty well, and I was turning 5300ish RPM's and seeing 42-43mph. Once loaded with 3 adult men and my son and a full tank of bait and all gear I was seeing 5000rpm's at 38-40mph. Couldn't trim out much loaded or the nose would bounce but the lake was pretty choppy as well. The prop tested this weekend is an entry level SS Mercury prop, called Vengeance. I need to purchase a prop now and am wondering if I should drop to a 16" pitch to get a few more overall RPM's or if a more performance prop will do the trick and I can stay with a 17P and keep that topend speed. I don't know a lot about the Performance Vent System props by Mercury but an enertia was suggested where you can put in different size exhaust plugs to achieve quicker performance but that is a pretty pricey prop as well. I do not mind spending the money if it is worth the money I just don't know a lot about the differences in what are concidered entry level/consumer props vs performance grade props. Thanks for any suggestions, What are you guys seeing on your Center console boats when your loaded up?

[drag4striper]

Chris, I have a SS Mercury Vengeance on my boat now
# 48 - 16988 , 18p.
You are welcome to try it out sometime.

[bushwacker]

May 6, 2019 8:32:19 GMT -5 drag4striper said:

Chris, I have a SS Mercury Vengeance on my boat now
# 48 - 16988 , 18p.
You are welcome to try it out sometime.

Thanks Rich I appreciate the offer. With the 17P loaded down I was in the lower end of my motors Wide open throttle range so I think any thing pitched higher than 17 is gonna kill it. I have a 19P that came on the engine and it was a dog getting up on plane and only produced 4800rpms.

[johnr]

I'd go with the smaller pitch just to have the available RPMs if needed.

[hotdog]

If the 15 pitch gets you 6000 rpms unloaded, you should be real close when loaded to fish. Do they have a 15 pitch with a slightly larger diameter?
I'd try that or go to the 16 pitch.
I'm no expert but I've always read your prop should let the engine run near max rpms at WOT with a normal load on the boat.
Good luck.

[bushwacker]

I never updated this post after I found the best prop for my set-up. I ended up going with a Mercury Enertia in 16 pitch. I am turning 5500 RPM's and it's pushing the boat at 42-43 Mph with a light load. It has a great hole shot. Loaded down it still comes out of the hole good and I still push 40-41 mph. I can back it down and cruise at 24-28mph with out the nose being in sky too much. The boat is very smooth all around with the new engine and I love the hydraulic steering. These SS props are very expensive but I was able to find one on Ebay for half price and hardly used. PROPS MAKE A HUGE DIFFERENCE and just a pitch can make a big difference. It was a little frustrating at first but well worth it in the end to make sure I found what my boat liked the best.

[greywalls]

Did you end up raising the Merc any, in connection with getting it dialed in?

[bushwacker]

Aug 23, 2019 8:50:52 GMT -5 greywalls said:

Did you end up raising the Merc any, in connection with getting it dialed in?

I did not need to raise the engine up any. I thought it may be too low are first but my trim calibration on my new digital gauge was way off. I thought I wasn't getting any trim before the noise would bounce but in fact I was trimmed too far up. Now when I am trimmed to my sweet spot the top of my cavitation plate is just above the water skimming.