boat spped/prop questions

[jonnysteals]

I do not know if this was posted in the right section. I have a 2004 palm beach 205 with t-top and a suzuki df140. I bought the boat with a rusted motor mount. I replaced that myself after receiving a 3500 quote. Overall I replaced the engine moutn in 7 hours with the help of my father in law. That is not the problem. I have put around five hours on the boat and it seems to be a good runner. My issue is with the boats performance/speed.

The palm beach 205 weighs 2400 pounds according to the manufacture. It also holds 87 galloins of fuel and is currently full. I have a 2002 suzuki df140 which weighs anouther 450 pds. I had around 600-700 pounds of people/gear on board. At WOT(5500) rpms I can hit 27-28 mph. This is gps verified not by the spinning wheel. IS this reasonable for this engine boat combo. I woild prefer to be around 35 mph.

My prop is a three blade stainless piece. I have searched for the pitch and details but they are not printed on the prop anywhere visible to the outside. What prop should I be running for this boat/motor combo. If changing the prop effects my wholeshot I dont believe it is worth it. I believe getting on a plane is more important. I did some reasearch and it seems my redline is 6200. This means I can change my pitch by -2 and pick up 400 rpms. I do not know my current pitch so I am open to recommendations. Below are pictures for my boat/prop

BOAT

prop pic 1

prop pic 2

motor height

motor height 2 and I think my fish finder trnasducer is mounted too high as well

Any help suggestions for a prop would be great. I would love to do 35 mph WOT but I really dont want to sacrifice my holeshot too much.

 

[reddogg]

Re: boat spped/prop questions

I used to have a similar hull and a 150 on it. I got 40mph (gps) with a 15 x 15 stainless steel prop when I'd go out solo. With the added weight of fuel, gear and people what your getting dosen't seam unreasonable.

red

 

[jonnysteals]

Re: boat spped/prop questions

Yea I plan to only run around a half tank besides when I head offshore. The boat rides awesome but I got passed by much bigger boats. Does any one know the ideal prop for my boat weight. It's hard to find prop info for my Suzuki. All help is appreciated

 

[H20Rat]

Re: boat spped/prop questions

So you are under your redline by 400? That would indicate you should go to a slightly lower pitch. Given that you are just barely under, it isn't going to change your speed much if you do change to a lower pitch. Recommended operating rpm is usually about 400 or so less than max redline rpm anyway.

Honestly your setup looks fine, the motor is high but as long as it isn't cavitating that isn't a problem. Lowering it without reason will hurt your performance. You are simply pushing a lot of weight (4000 pounds give or take) with not a lot of engine and a hull that has a fairly deep V without much for lifting strakes.

 

[Chris1956]

Re: boat spped/prop questions

I have a 21 foot Bow rider with a Johnny 2 cycle 150HPV6. I can get just about 40MPH (GPS measured). My setup must weigh at least as much as yours, likely more. I therefore think you have a motor issue. I do not know the gear ratio of that Suz, or I could give better advice. I run a 19" pitch alum prop.

You might take a colpression and spark test on that motor and post results in the correct motor forum.

 

[Home Cookin']

Re: boat spped/prop questions

My 21' center console is very similar to yours; I have a 150 Yam 2 stroke. My top end is slightly over 40, but I seldom run it up there.

I also have a painted bottom like you do; I think that costs us about 4 mph. I do not have a T top; that will cost you a couple MPH (I haven't run the numbers but I feel it when the bimini is up). I also have 10 HP on you, so that has to be worth a few MPH. I have a feeling I might not be getting all my gas, as I have a dead zone at the top end of the throttle.

Even a light wind changes the MPH a few points. I also have trim tabs; looks like you don't.

You seem concerned about hole shot; not sure why unless you pull waterskiiers as a primary function, or need to hop up out of shallow water. The 2 second delay on getting on a plane is seldom as important as your cruising speeds/performance. Trim tabs will fix that and give you a great hole shot while keeping a good prop for the upper range.

Also, for general use, most open-water boaters don't run WOT/top speed regularly. Look at what your boat does at 3500-4500 since that is where you will likely be running. Teh top end numbers are typically to verify your set-up, but not for your optimal running speed.

I tried about 8 props this winter to replace my stock aluminum with a stainless. Diameter made a big difference. It did not work out as simply as an inch of pitch equally so many RPM, and there was a wide variety of performance in the mid range, which I focused on as much as top end. Also SS is heavier so it has a different effect that a matching aluminum.

You can't start prop shopping until you get your numbers off your prop. Look under the washer. Then find a prop shop that will let you try them and return them.

I think I ended up with a 17 but I have to check.

Hate to say it but your boat may be a little under powered; I sometimes wish I had a little more that 150, eventhough, as I said, a higher top speed is not big on my agenda. But I still like to cross the smooth water to my destination quickly, to have more time to fish, or to outrun a squall.

 

[jonnysteals]

Re: boat spped/prop questions

My 21' center console is very similar to yours; I have a 150 Yam 2 stroke. My top end is slightly over 40, but I seldom run it up there.

I also have a painted bottom like you do; I think that costs us about 4 mph. I do not have a T top; that will cost you a couple MPH (I haven't run the numbers but I feel it when the bimini is up). I also have 10 HP on you, so that has to be worth a few MPH. I have a feeling I might not be getting all my gas, as I have a dead zone at the top end of the throttle.

Even a light wind changes the MPH a few points. I also have trim tabs; looks like you don't.

You seem concerned about hole shot; not sure why unless you pull waterskiiers as a primary function, or need to hop up out of shallow water. The 2 second delay on getting on a plane is seldom as important as your cruising speeds/performance. Trim tabs will fix that and give you a great hole shot while keeping a good prop for the upper range.

Also, for general use, most open-water boaters don't run WOT/top speed regularly. Look at what your boat does at 3500-4500 since that is where you will likely be running. Teh top end numbers are typically to verify your set-up, but not for your optimal running speed.

I tried about 8 props this winter to replace my stock aluminum with a stainless. Diameter made a big difference. It did not work out as simply as an inch of pitch equally so many RPM, and there was a wide variety of performance in the mid range, which I focused on as much as top end. Also SS is heavier so it has a different effect that a matching aluminum.

You can't start prop shopping until you get your numbers off your prop. Look under the washer. Then find a prop shop that will let you try them and return them.

I think I ended up with a 17 but I have to check.

Hate to say it but your boat may be a little under powered; I sometimes wish I had a little more that 150, eventhough, as I said, a higher top speed is not big on my agenda. But I still like to cross the smooth water to my destination quickly, to have more time to fish, or to outrun a squall.

I will pull the prop this week and see the numbers. I do believe that my boat is a underpowered. I think that it truely needs around 200 horse power. My boat is just heavy. The heavy boat is something I wanted because I wanted to go out in the ocean with this boat. I can certainly live with my boats performance I was just hoping that I can improve its performance with the motor I have. I also bought this boat for a great deal. The previous owner told me the motor was blown because it kept stalling out. It had a bad engine mount and was chocking itself out on exhasut fumes. I have a spare evinrude ovean pro 150 two stroke as a back up just in case. I want to keep the four-stroke because they seem so much better on fuel

I am concerened about holeshot because this boat is my all-pupose boat. There is my one creek that I like to go to that you can only get to on a plane. Its right after a no-wake zone so you got to be able to hop up on a plane rather quickly. Overall I love this boat. I was able to drift the inlet and catch a few flounder yesterday and I generally did not get tossed around much.

I also do not think there is anything wrong with this boat. I dont remember compression numbers off the top of my head but they were fine. The thing runs fine and can idle all day when drifiting. This is my first four-stroke and I sometimes think it stalls out when its idling because its so quiet. WOT it is a little quiter than my two stroke the but the idling noise is quite drastic.

I have a stupid question is there any forumla to calculate what prop I need or is this sort of a guessing game. I mean I know my weight/and my motor details. It seems to me that there should be something I could plug my info into to tell me what prop would best suits my needs. I really dont want to be guessing with props costing over 100 bucks a pop for the aluminum ones.

 

[craze1cars]

Re: boat spped/prop questions

Not many stainless props out there that don't have a pitch number stamped on them...

Have you pulled the prop off your motor? Likely you'll find a pitch number stamped somewhere hidden...under the retaining nut/washer, below the housing, inside the hub...

Even if there are no markings, a good prop shop can identify the pitch for you. Keep in mind that a good propeller shop can also repitch a stainless prop up to 2 inches. My local shop does it for $10 per blade...and does a very nice job. I was able to fine-tune my boat by about 150 RPM by having 1 inch removed from a 4 blade 21 recently. Of course if you need or want to actually clean up nicks and repair some minor prop damage the price will go up substantailly....by maybe $100 or so. But that's still not bad, and you end up with a brand new stainless prop of a custom pitch for your boat. So before you spend money guessing on aluminum replacements, why not give your current stainless (which is better than aluminum anyway) prop to a local prop shop and see if they can take two inches of pitch out of whatever it is now? That will give you a few hundred RPMS if that's what you want, improve your holeshot, and just maybe help you a teeny tiny bit with to speed...shouldn't hurt anyway.

I found a reference that says your motor has an operating range of 5800 to 6200. I cannot guarantee this is accurate. But if it is, this generally means it is the range where the motor makes its peak 140 hp. So if you're spinning only 5500, you might only be making 130-ish hp...costing you top speed...lugging the motor a hair...and hurting your holeshot all at the same time.

Get those RPMS up a little bit by repitching your existing prop, and you might actually make the boat faster while also improving holeshot. That's the direction I'd go anyway if I had a nice looking stainless prop already in my hands....it probably would be your cheapest and most accurate option, especially if you are starting with an unknown pitch.

 

[jonnysteals]

Re: boat spped/prop questions

Not many stainless props out there that don't have a pitch number stamped on them...

Have you pulled the prop off your motor? Likely you'll find a pitch number stamped somewhere hidden...under the retaining nut/washer, below the housing, inside the hub...

Even if there are no markings, a good prop shop can identify the pitch for you. Keep in mind that a good propeller shop can also repitch a stainless prop up to 2 inches. My local shop does it for $10 per blade...and does a very nice job. I was able to fine-tune my boat by about 150 RPM by having 1 inch removed from a 4 blade 21 recently. Of course if you need or want to actually clean up nicks and repair some minor prop damage the price will go up substantailly....by maybe $100 or so. But that's still not bad, and you end up with a brand new stainless prop of a custom pitch for your boat. So before you spend money guessing on aluminum replacements, why not give your current stainless (which is better than aluminum anyway) prop to a local prop shop and see if they can take two inches of pitch out of whatever it is now? That will give you a few hundred RPMS if that's what you want, improve your holeshot, and just maybe help you a teeny tiny bit with to speed...shouldn't hurt anyway.

I found a reference that says your motor has an operating range of 5800 to 6200. I cannot guarantee this is accurate. But if it is, this generally means it is the range where the motor makes its peak 140 hp. So if you're spinning only 5500, you might only be making 130-ish hp...costing you top speed...lugging the motor a hair...and hurting your holeshot all at the same time.

Get those RPMS up a little bit by repitching your existing prop, and you might actually make the boat faster while also improving holeshot. That's the direction I'd go anyway if I had a nice looking stainless prop already in my hands....it probably would be your cheapest and most accurate option, especially if you are starting with an unknown pitch.

The rpm range is correct. The tricky part is that 6200 rpm is the readline. I have read that if you held over 6200 for over ten seconds it will cut the power and you have to go to neutral than back into gear. I do not want to push the rpm's too much. I would like to me around 5900-6000 max. I think that when I find my pitch if I adjust it by -2 that should give the rpm's I need.

I have not had the prop off yet. Thats about the only part I have not touched. I have pulled the lower unit throuh power head but thats about it. I will be playing with the boat this week hopefully.


One more question. Doesnt the transducer for my fish finder look to be mounted to high on the transom. I always though the transducer was supposed to hang below the bottom of the hull so that it gets unobstructed water. I can not cruise over 9mph and the fish finder read the bottom. I would like for it to read at all speeds. Will moving it lower rectify this problem. If so cna I seal the holes with 5200 when I relocate the fish finder? Sorry for the million question this is my first nicer boats I have owned and dont want to mess this one up.

 

[sschefer]

Re: boat spped/prop questions

Lowering the transducer may not be the answer your looking for. If you're looking for accurate sonar/depth readings at speed then a through-hull transducer is what you need. Depending on the head unit, you may be able to get a switch so you can go from stern for fish finding to through hull at speed. As a side note, we used to call them skimmers because at speed you want it just barely skimming the water. Looks like yours is probably setup a little high and you could lower it but it probably still won't give you very good readings at speed.

 

[jonnysteals]

Re: boat spped/prop questions

This fish finder is temporary. I will be ordereing a new one but my budget is blown this year. I was not planning on a new boat and well bought one. THanks for moving my post to its correct location. I dont know how I missed this spot. Any help is appreciated; lots to learn in the boating world

 

[jonnysteals]

Re: boat spped/prop questions

I havent pulled the prop yet. Lifes been crazy lately and I have been just using the boat ever night after work.
I also mispoke about the rpms. What I thought was 5500 rpms was only 5100-5200 rpms. When standing and driving your look at a downward angle and makes it look like 5500 rpms. If I look at it from directly in front of it is is only 5100-5200 rpms. I have found reports of a similiar boat with a 140 going 38 mph with 2 people and 35 mph of fuel. If I dont go fishign tonight I am going to pull the prop. I also put new fuel filters and spark plugs and it make no difference on the rpms. I di my external fuel filter and the low pressure fuel filter on the back of the motor. The dealer did not have the high pressure fuel filter in stock at the time. Motor has right around 600 hours on it.

 

[craze1cars]

Re: boat spped/prop questions

Well, given your new figures, now you're a full 1,000 rpms short of what you need. You're really lugging that motor. 1000 rpm gap is way beyond the reach of a repitch...so I now retract my previous recommendation that I wrote above.

Still need to know your current pitch in order to recommend anything...

But by the book, it seems you probably need to drop a solid 5 inches of pitch from whatever you're running now...

 

[jonnysteals]

Re: boat spped/prop questions

I removed my prop. Its a 14x18 suzuki 3 blade prop. This concerned me so I called the previous owner. He said that well the boat is just under powered. He said he would go around 28-33 according to the fish finder.He may get 35 mph by himself with not much gas and gear. I am getting 28 mph gps with a full tank and 600pounds of gear/people. I think I am just underpowered. IS there any help in switching props or am I as good as I am going to get with this prop. The motor seems to run great. Gets around 1 gallon per hour with me running at 5100 rpms 90 percent of the time. I filled up last time and it took 22 gqallons for 25 hours of run time. I have put an additional 12 hours on the motor since then. It starts and runs fine; just slow.

I think with my heavy boat and the deep v I am just under powered. Any recomendations. I do not have the money to repower this boat. I am going to keep using to keep this motor/boat combo for a few years.

 

[craze1cars]

Re: boat spped/prop questions

Seems to me that a lower pitch prop is certainly warranted for your setup...it should help your holeshot/planing, maybe get you a little more speed (or maybe not), and it will prevent you from continuing to lug the motor.

Now that we know you have an 18, I think maybe a 15 or a 13 pitch would be better all-around.

And Smart Tabs are a fanstastic band-aid for underpowered boats...

 

[jonnysteals]

Re: boat spped/prop questions

yea it takes around 8 seconds to currently get on to plane. What is driving me crazy is at my marina I see tons of similar sized boats with a 150 and they all seem to do high 30s. Is a 15 degree prop something I could find on the shelf or is a special order item. Thanks looking for all the help I can get

Would I benefit over a 4 blade prop vs the 3 blade I currently have?

 

[craze1cars]

Re: boat spped/prop questions

15's are common. (Just an FYI, a 15 pitch prop is measured in inches, not degrees).

4 blade sometimes sacrifice top speed a bit. As that seems to be a priority of yours, may not be a great idea. They do help with planing and sometimes feel smoother.

 

[jonnysteals]

Re: boat spped/prop questions

Would you recomend the 15 or 13 degree prop? I need to talk to my marina and see if I can do a trial run on one of these props. So smart tabs help out underpowered boats by pushing the front down and allowing it to plane faster. My quesdtion is once I get up to plane do I lift the trim tabs up? Sorry for teh thousand questions; I am trying to learn before I go throwing money at something that might not solve the problem.

 

[craze1cars]

Re: boat spped/prop questions

Smart Tabs lift the rear of the boat...effectively pushing down the front. Yes, it helps them plane faster because the rear doesn't dig and plow so deeply at slower speeds.

They are automatic, operated by spring/shock absorbers, so water pressure will cause them to lift up flat when you are at speed, assuming you have purchased the correct size. When you slow down, the springs/shocks push them back down to help keep the rear of the boat up. They generally do not impact top speed at all. Visit their website for more info.

I don't honestly know whether a 15 or 13 inch pitch prop would be better for you. You just need to try one out and see what your RPMS are. Something in my gut is telling me you should try the 15 first...that might just be indigestion, though....

 

[jonnysteals]

Re: boat spped/prop questions

Thanks for the help. I will have to look into the smart tabs. For right now I am trying to convince my local dealer to let me borrow a 15 inch prop to see how my boat spins it. So far they are hesitant and I even offered to pay for it first. I just want to be able to return it if it does not help. My goal is to do 35 mph WOT. I only hope one day I can achieve that with my 140.