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More power for a AQ125A

tjmxer

New member
"I recently purchased a Baylin

"I recently purchased a Bayliner Trophy Fisherman 2060 with a Volvo Penta AQ125A and 270D outdrive. It runs great, starts right up, idles, etc. The problem is, its very hard to get the boat on plane and to keep it there without the trim tabs all the way down. I just installed a Stingray Hydrofoil and it seemed to help, although, with more than three people on board I can not keep it on plane without the tabs all the way down. Also, in that configuration, rpm's at WOT are 4000. With only one ot two people on board, I can take the trim off the tabs, only once its on plane and only after the speed gets to over 26 or 27 mph. Still seems like the rpm's are low compared to what other posts are saying is ideal. I cant find a pitch number on the prop but I did find what looks like a part number. C854997 and another number, P388. Any suggestions on how to improve performance of my boat? In addition to changing the prop, if needed. I'm not looking to pull wakeboarders or anything, but it would be nice to get on plane quickly and run 35 mph. Any suggestions will be greatly appreciated."
 
"Whoah, that's a 20 foot b

"Whoah, that's a 20 foot boat? Your motor is only rated at about 120HP, I'd be very very surprised if you can get it up over 30 MPH under any conditions with that motor.

A quick Google search shows a 0854997 is a 15x17 prop. Your WOT should be somewhere up around 4800 or 5000 so you might try a 15x15 for a better hole shot, if that's not enough, maybe a 15x13.

Just for comparison, I have a AQ131A (120hp) on a 16 foot Capri and I run a 15x17 at about 5000ft altitude and it's about perfect. WOT fully loaded is about 4800. My speedo's busted but I had a GPS out last year and seem to remember being able to run 32 or 33 mph wide open. Cruising at a more sensible RPM was under 30 MPH, if I remember correctly.

If I can't run 35 in a 16 foot open-bow boat, no way are you going to do it in a cuddy cabin 20 footer. But try switching that prop, it might pop you up on the plane a little faster."
 
"This past week on vacation I

"This past week on vacation I had it 31 mph(fishfinder speedo) with three people on board, but it took awhile, and I still needed the trim tabs to get on plane. Engine speed was around 4300-4400 at that speed, if I remember correctly."
 
I have the same boat and motor

I have the same boat and motor running a 15 X 17 stainless prop. My top speed is 30 mph at 4700 rpm with 4 people in the boat. I have a Whales Tail on the outdrive and trim tabs which are needed to get it on plane quick.

Keep in mind that these boats where built for fishing and fuel economy during the 80's gas crisis. They were never intended for high speed. They are good strong boats with great engines and outdrives. They will take you offshore to the fishing grounds and bring you back. If you want something that goes fast for tubes and ski's you bought the wrong boat.
 
"Thats incredable.I have a AQ1

"Thats incredable.I have a AQ145a - 16ft boat,138hp and I can only get 22 Mph with 2 people on board.I run a 15 x 17 prop.How do you do it."
 
"tim,

That's pretty dar


"tim,

That's pretty darn good for a boat that size!!

Mine is an 88 Volvo AQ151B 150 HP in an 18 ft bowrider and i can get around 47 mph at top end.

I run a 15 x 21 pitch prop that i put on,it came with a 15 X 19 pitch but topped out too quick for me.

Takes a minute to get on plane,stands straight up for about 20 seconds,but get much better top end with the 21 pitch prop...we like to use it for tubing and ski.

Thats a big boat Tim,but i would experiment with different pitch prop's. You should be able to get right or left props cheaply on Ebay, i carry a couple extra's with me.

Thats whats nice about Volvo's, You can run R or L props by unscrewing the gearcase cover and swapping the rod the other way.
---------------------------------------------
Stan, you should try a 15 x 19 pitch that boat should do an easy 40 mph!"
 
"Tim, you won't be able to

"Tim, you won't be able to run at 35 mph with your engine and boat. If you were to run your engine at 5000 RPM (I wouldn't), with a 15x17 prop and with a 2.15:1 gear ratio in your outdrive, your boat would get a theoretical speed of 32.5 knots, and if you factor about 15% slippage, the real speed would be about 27.6 knots.

Brian, with a 15x19 prop and at 5000 RPM, you would get a theoretical speed of 36.3 knots, and a real speed of just below 31 knots. IMO, 40 MPH is just out of the picture unless you get a strong wind by the stern and a 7-10 knots current in your favour."
 
"El,

Here we go again....I&


"El,

Here we go again....I'm starting to think you just like to argue?

Do you base all your life off of theory,or are you here with the rest of us?

EVERY SINGLE 140 HP 16 to 18 ft boat i service at the marina can achieve a minimum of 38-40 mph....so i have no idea what you're talking about El?

here's a 17.5 + ft boat shootout, the Bayliner 17.5 ft 135 hp boat has a horsepower of 135 and will do 44.5 Mph.....In reality,...not theory.

http://www.boatingmag.com/article.asp?section_id=4&article_id=1356

All 4 boats get over 40 mph and all boats are 17 foot plus+, yes..even the Volvo 135 hp 4cyl.

End of discussion."
 
"Brian,

The boats in your


"Brian,

The boats in your link could only achieve the 40 miles if equipped with a larger propeller than a 19" and by running the engine at higher RPM.

I will make it simple for you. A VP OHC 4 cyl engine running at 5000 RPM (few 4 bangers keep that speed) will give in a 2.15:1 gear ratio outdrive 2325.6 shaft RPM. A propeller with 19" pitch would push the boat a total of 44186 inches per minute, or 2651162 inches per hour, which means about 41.8 land miles per hour (divide by 1.15 to obtain nautical miles per hour or knots). Factor in at least a 10% or more slip and you fall a few miles short.

Like it or not, everything you are dealing with (engines, boats, propellers, etc) have been calculated mathematically by someone. That your math does not seem to be the greatest is a poor argument to disregard math and physics applied to boating."
 
"In my opinion Mr. El Pescador

"In my opinion Mr. El Pescador is correct. It is called math and physics, which is the basis for all things mechanical and how fast or how high we can go. If you argue with the math you are going to lose."
 
"Ok, ok, relax guys! I checked

"Ok, ok, relax guys! I checked that speed with a GPS also and got the same result, +/- 1 mph. And that was at only roughly 4200 rpm. I realize my boat is huge for the little Volvo 1 barrel 4 cyl. I've had a 20 ft. Penn Yan with a 3.8 V6, a 21 ft. Cruiser cuddy cabin with a Mercruiser in-line 6 and a 25 ft. Sea Ray with a fly bridge and 9 1/2 ft beam and 330 hp mercruiser. All of these boats topped out at 30 mph other than the Cruiser, that would do 35. All I'm saying is that it seems like the little Volvo is very sluggish and will not stay on plane with more than 3 people on board, which was probably 22-25 mph with the trim tabs fully lowered. I got 31 mph with 2 people, no trim, only after it was on plane for a few minutes. And that was approx. 4500 rpm. With a different prop pitch, for more power and less speed, keep the boat on plane? Since now at 25 mph the ass sinks like a stone without the tabs? Can I lift the outdrive with the power trim while at full power to see if the outdrive angle would make a difference in plaining? I have a 270D outdrive. Right now i have the outdrive pin set in the middle position."
 
"My only comment to Brian King

"My only comment to Brian King is... How does the guy on the slalom ski feel while the boat is standing straight up for 20 seconds, waiting to pop up out of the water?
lame.gif
"
 
"Tim, I suggest that 4000-4300

"Tim, I suggest that 4000-4300 RPM at WOT is too low and that will overload the engine. You may want to consider trying a 15x15.

I just looked at Casey P's figures (4700 RPM, 17" pitch, 30 miles), which gives a propeller speed of 35.1 mph and a propeller slip of roughly 15%. I would expect the propeller slippage in yours to be similar or even slightly worse if you use an uncupped aluminum propeller."
 
"Bob.
I didn't say it did


"Bob.
I didn't say it didn't move forward.
light_bulb.gif


Casey,
you know what they say about opinions?
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El,
Will you be my teacher?
lol.gif

I'll make it simple for you....bigger faster,smaller slower,lefty loosy,righty tighty.

Jesus your a trip man...you really make me smile!
Can i borrow your pocket protector?"
 
"Brian,

So that you know, I


"Brian,

So that you know, I have too many things to do, but I still manage to find some time to try to help (to the best of my abilities) other boaters who do not have the resources to pay a mechanic to fix their boats. I do this as a hobby (I do not get paid for it), and the last thing I want to do is to waste my time engaging in pissing matches with people who behave like grade 5ers. If this is what you are looking for, I suggest you better look in another forum that better suits your personality.

If, on the other hand, you came here to learn something (not just from me but from others as well) or to try to help others, then I strongly suggest you start by leaving your ego aside and behave like an adult. That is, in the event you are actually an adult and not an 11 year-old.

Thank you."
 
"El, I am grateful for the hel

"El, I am grateful for the help you have given me in the past, and it was right on the money. Advice is like many other things in this world. If you don`t like it, DON`T USE IT."
 
"El,

Come on man, I'm j


"El,

Come on man, I'm just razzing you. I too am here to help people and share my knowledge. But when you poke at me expect to get poked back.

I can act like an adult...though my girl may argue the contrary.
lol.gif


I do work as a marine technician for a living and have worked on internal combustion engines most of my adult life. And if what I say doesn't agree with your thoughts,know that i make my statement based off my experience...in an effort to help. I'm not always right because whenever you think that....you'll be taught another lesson...the hard way.

I apologize if I offend, now can we get back to whats at hand...helping tim?"
 
"I looked back at some of what

"I looked back at some of what El wrote and
I dont know what to say about what he said about my boat not being able to go 35 mph without turning 5000 rpm. I just had it 31 mph at 4200 rpm and it was confirmed with both a gps and my very expensive, Bottom Line fish finder. Would it be possible I have a different ratio in the gearbox? And any comments on what I wrote about raising the outdrive with the the power trim to change the outdrive angle to help keep the boat on plane?"
 
"Tim, you can always try to ch

"Tim, you can always try to change the trim pin and see where the boat behaves best. Now, if you want to use the lifting device to change the trim, make sure your boat has power trim (hydraulic) and not power tilt (electrical). You cannot use power tilt for that purpose, unless at very slow speeds."
 
"How can I tell the difference

"How can I tell the difference? If its hydraulic, doesn't an electric motor operate it? I have a trim toggle switch on the dash with a red light that goes out when its fully lowered. What pin position will help keep the nose down? Its in the middle now. Ran it in the lower/forward hole for a bit and didnt seem to help, maybe made it a little worse. Didn't get a chance to try it in the rear/upper holes."
 
"tim,

I don't think you


"tim,

I don't think you will need to change any pins, can't you just toggle the angle as you drive?

Raising and lowering the stern-drive trim will have a big effect on planing and speed of your boat."
 
"Tim, please do not pay attent

"Tim, please do not pay attention to King Brian. He does not seem to understand that on a Volvo Penta AQ engine the angle of the drive cannot be changed "as you drive" (wow, that's a very "marine" expression!!!) if you have power tilt. Power tilt is a mechanical device meant only to raise the outdrive, but not to withstand thrust from the propeller.

How to tell the difference? Look at the port (left) side of the transom shield from the inside of the boat. If the lifting mechanism is like the one on the picture, you have power tilt, and you cannot use it the way you suggested.

http://image8.usedvictoria.com/YYJ9580989.1.jpg"

The pin closest to the transom shield will help you to keep the bow down, but it may make the ride too hard and sluggish at high speed. That is why you have to experiment and see which of the three positions of the trim pin work best for you."
 
Brian:
Time you learn the dif


Brian:
Time you learn the difference between trim and tilt.
(power)trim you may use at any speed.
(Power)tilt you may at the worst only use at low idle!
 
If you use "Tilt" at h

If you use "Tilt" at high speed to try and trim your boat you will as a minimum damage your tilt mechanisim. i.e. bend or break the vise rod in it. You would also risk breaking the housing which is part of your transom shield. Now your talking about major $$$$$ to repair.
 
"Just to add.
In (electro


"Just to add.
In (electro) hydraulic system you have both. A 'trim' area and then a 'tilt' area. If running the engine in the tilt area, you may risk both to damage the u-joint and perhaps even worse, rip apart the bellow! That is why I said 'in worst case' above."
 
The original post said this wa

The original post said this was a 270D drive.
VP270s (despite the "course" link provided...which states "many" not ALL drives) only came with power tilt.
 
"Yep, your right guys. Power t

"Yep, your right guys. Power tilt only. Now back to my latest question. El stated that there was no way i could get that speed out of my boat with the ratio that "should" be in the lower unit, prop and rpm. Could it be possible that there is a ratio other than 2.15:1 causing such a low rpm with 30 mph and the prop I currently have? How can I tell exactly what the ratio is? Also any suggestions, after reading all of the above posts, on what size prop I should get that will improve my boats performance to an acceptable level(get and stay on plane in a reasonable amount of time and run @ 25 mph, at least)?"
 
"Tim, to know the ratio, move

"Tim, to know the ratio, move the propeller so that one of the blades points toward the exhaust in the outdrive, then make a reference mark on that blade and another one on the outdrive (both marks have to line-up). Put the outdrive into gear and turn the engine slowly with a socket and a ratchet while you have someone watching the marks and stop when the marks do line-up again. If you turned the engine 2.15 times for one complete revolution of the prop, then the gear ratio is correct for your engine. If you turned the engine 1.61 or 1.89 times, then the gear ratio is for a V6/V8, or for a 6 cylinders inline, respectively.

Another possibility is that your tachometer may be faulty or wrongly set, or it has a faulty connection.

Keep in mind that it is not impossible to do more speed in practice than in theory, but in those cases the boat is getting an extra push from either currents or wind.

When it comes to propellers, a rough rule of thumb is that a decrease of 2" in pitch will result in about 400 RPM increase of engine speed, and the other way around if you increase the pitch. Therefore, you may want to try a 15x15.

If you are curious about propellers, I suggest you take the time to download and read this document, it will answer some of your questions.

http://www.michigan-europe.com/images/pdfs/propeller-basics.pdf"
 
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