Propper Props???

[LV2FISH4CATS]

ok... going to try and make this easy to read.

i have a evinrude 140 hp outboard motor. looking to change props. i am running

a 13.75" X 15 now. Looking to gain top end and help plane out better. I do not

know a lot about props and the changes that a new prop will make. Can anyone

please give any info on how to pick a prop and what would a 13" X 19 do compared

to the old prop I am running?

Thanks for any help
Larry

 

[JB]

Re: Propper Props???

Trying to read your post made my brain hurt. I think you have an engine problem of some sort, but I am not going to try to dig it out.

Please fix your post so it is readable.

 

[tashasdaddy]

Re: Propper Props???

loose the caps, hard to read. edit your post.

 

[LV2FISH4CATS]

Re: Propper Props???

Changed post to help make it easier to read... reduced the amount of info.

hope this helps.

 

[Silvertip]

Re: Propper Props???

What makes you think you can simply slap a 19P prop on your engine and gain speed. Don't you think the engine must have sufficient power to actually twist that prop. If that reasoning was true, every engine from a 2 HP to 500 HP would be using a 30P prop. So here is what you need to do. Go to the Prop Forum which is where this should have been posted. Then look at the stickies at the very top of the forum. You will find one titled READ THIS FIRST. With the information you've provided we don't have a clue what to tell you and besides, you may already have the best prop for your boat.

 

[JB]

Re: Propper Props???

This really is a prop question. Moving it to the Prop Forum.

 

[LV2FISH4CATS]

Re: Propper Props???

What makes you think you can simply slap a 19P prop on your engine and gain speed. Don't you think the engine must have sufficient power to actually twist that prop. If that reasoning was true, every engine from a 2 HP to 500 HP would be using a 30P prop. So here is what you need to do. Go to the Prop Forum which is where this should have been posted. Then look at the stickies at the very top of the forum. You will find one titled READ THIS FIRST. With the information you've provided we don't have a clue what to tell you and besides, you may already have the best prop for your boat.

Hey Silvertip. Sorry I am NOT as informed as you. If you would have tried to read my post you would have seen that I ASK for help and SAID I did not know anything about props. that is why I am on this post. I just found this site last night and thought it would be a good place to start and find fellow boaters who know more than I do so i could pick there brains and get good info. But from the answers I have got all I can say is I am glad I have never run into your type of help out on the lake. Again I am new to this and was looking for help. But found NONE. Just a few smart #$$ guys not willing to provide any help just an attitude for not posting something in the right spot or for those who seem to be challenged in retaining what they read so much so it gives them a headache. I will not recomend this site to anyone who needs help or needs info.

Sorry I took up so much of your time.

 

[JerrfyLube]

Re: Propper Props???

But from the answers I have got all I can say is I am glad I have never run into your type of help out on the lake. Again I am new to this and was looking for help. But found NONE. Just a few smart #$$ guys not willing to provide any help just an attitude for not posting something in the right spot or for those who seem to be challenged in retaining what they read so much so it gives them a headache.

You'll find LOTS of that on this forum...

 

[Bondo]

Re: Propper Props???

Quote:
Originally Posted by LV2FISH4CATS
But from the answers I have got all I can say is I am glad I have never run into your type of help out on the lake. Again I am new to this and was looking for help. But found NONE. Just a few smart #$$ guys not willing to provide any help just an attitude for not posting something in the right spot or for those who seem to be challenged in retaining what they read so much so it gives them a headache.
_________________________________________________________________

You'll find LOTS of that on this forum...

Ayuh,...

I guess you fellas expect Miracles,....

You provide absolutely No pertinent Information,+ expect an Answer,..??..??

That's Why there's a "Read This First" sticky....

 

[LV2FISH4CATS]

Re: Propper Props???

I Posted All The Info Needed The First Time I Posted. Boat Type, Length, Motor, Hp, Dia And Pitch Of Prop Now Being Used, And The Problem I Was Having. I Was Asked To Repost So The Could Read It...seems I Am Not The One Who Has Had The Same Issue With Smart #$$ People On This Site

 

[steelespike]

Re: Propper Props???

We come here to help; some of us don't have as much patience as others.
Please don't take iboats forums badly in the end we want to get you going.
As far as props there are stickies at the top of the page. Basically we need all the info on your present setup to be able to tell what you need.Motor brand,year and hp.,max rated rpm if you know, Boat type(brand and design)present prop size,max rpm and speed.Your typical load and activities.Your motor must be able operate near the top of its recommended rpm range.Selecting a prop is like picking a single gear in a car to do everything there has to be comprimises.Please get us the info and we'll all do our best to get you setup.

 

[steelespike]

Re: Propper Props???

Great guys, way to make a new guy feel welcome.You know some of us can't compose a message as smoothly as others and PATIENCE with a newcomer is a must. Think back to your first time on I bet you were a little awkward and un informed.You may have even posted in the wrong section etc. etc.
I'm ashamed the way lv@fishforcats was welcomed and I appologize.

 

[bowman316]

Re: Propper Props???

You never said what type of boat you have?
Is it a pontoon? Because a 15 inch pitch is very little pitch for a 140 HP engine. I use a 15 pitch on my 70 HP engine, and that is almost not enough pitch for it, i just use it for water skiing.

Do you get on plane really easy now, high RPM's? I think a 19 may be a good idea, and if you can't turn a 19, something is wrong with your engine.

I am assuming that you don't have a pontoon, because they are different.

 

[boat1010]

Re: Propper Props???

Don't lose faith in the forum. There are people out there that can help ya. The pitch of a prop is a very hard thing to decide. The best way is to test. It you are running a 15p now and are running close to the manufactures RPM at WOT (wide open throttle) then there isn't much you can do but increase your HP. It depende on how much weight is in your boat. (do ya cary lots of people whe you ski) Do you have lots of gear in your boat?
The pitch of a prop is basicly how far it will move the boat in one revalution. a 13p under perfict conditions will move the boat 13 inches and so on and so forth. So if you would go to a 19p does your motor have the HP to push it? If you have too high a pitch prop it will never be able to get up to the higher RPM. Kind of like trying to start your car in 4th gear. Hope this helped ya a little. Hang in there.

 

[LV2FISH4CATS]

Re: Propper Props???

Thanks Steelespike for understanding a new comer.
I will try again to explain what I was trying to ask. If I say something that is not correct or you need more info just ask.

I have a 1976 Lund Tyee 20' I do not know the weight of the boat as the tag is worn off. It has a 1977 Evinrude 140 V4 Motor with a OEM aluminum 13.75 X 15 pitch prop. The boat runs out ok but has a hard time getting to plane and does not reach max RPM. Maybe it is a motor propblem and not a prop??It will run about 23 MPH with 3 guys.. say (600lbs) plus fishing gear. with only me in the boat it will run 30 MPH @ 3800 WOT. It is not that I want to go faster... I would just like it to plane out better. I trim the boat and it planes ok after a bit of distance. How much does the pitch of a prop effect the RPM?? I was wondering if a change in prop would make a difference and if I went to the 13.75 X 17Pitch prop. What would that do? Or what if I used a 14'X11 pitch?? I am learning and trying to understand how all this works..

AND.. It does use a lot of fuel.. Maybe I have carb issues and not a prop issue. I am learning and looking for and help.

Thanks for any helpful info.
Larry

 

[Tacklewasher]

Re: Propper Props???

Gonna ramble a bit here.

I think you have a motor problem.

I took a look at the Lund site and looked at the current Tyee. I think my situation is close enough for comparison.

For reference, I have an 1980 Evin 115. With a 15p prop I turn 5800 rpm and almost hit 40 mph on a 18' Starcraft aluminum boat. You are only getting to 3800 rpm. My setup is likely lighter than yours but for you to get to the same rpm would be a huge drop in pitch. The math would say to go down 10p to gain 2000 rpm, which is a stupid answer.

As a rule of thumb, a 1p change in prop pitch will change your rpm by 200. The higher the pitch, the lower the rpm. So a 17 would drop you to 3400 while an 11 would increase you to 4600.

But you really don't seem to be in the right area to start with.

Your motor is rated to run between 4500 and 5500 rpm and, the brighter guys than me here will recommend 5500 to 6000 with modern fuel to prevent coking problems (ask that in the Evinrude/Johnson forum).

Now, the number you give can't be right. You can't be seeing 30 mph with a 15p on that motor at 3800 rpm.

Using this tool, http://www.go-fast.com/Prop_Slip_Calculator.htm

Your gear ratio is 2. Put that in plus the 3800 rpm and 15p prop and, before any slip is taken into account, you would max out at 27 mph. Assuming 10% slip (common), you would be doing 24 mph.

Either your tach is off or you aren't going near 30. Is the 30 based on a gps or a speedo that came with the boat?

But, when all is said and done, I would think a 140 turning a 15p prop should be pretty responsive out of the hole on that boat.

I don't know how comfy you feel about testing a motor but there are some basics you can do easily (compression check, decarb) that may make a difference and some bigger things that you may not be comfortable with (carb rebuild, link-n-sync).

I'm thinking you need to make a post in the Johnson/Evinrude forum but be warned. The first comment will be to buy an OEM manual for your motor.

Before you go much further, you will want to be sure your tach is working right and that you know what speed you are doing by gps (the speedo's that come with boats are junk in my opinion).

And welcome.

 

[steelespike]

Re: Propper Props???

The Tyee appears to be fairly light at a about 1100 lbs.A 140 should easily push it to 40+ And get smartly on plane. I would guess the right prop size at 17 to19" the 2 most common causes of poor performance is motor problems.And excessive weight in the form of water absorbed into the flotation foam under the floor.Start with the motor first.See if its firing on all cylinders.See if any of the plugs are wet or fouled.Make note of each plugs condition.While your at it check the compression.Be sure the throttle is opening all the way.Is the idle speed at about 750 rpm?
If you have the boat on a trailer you might weigh it with nothing extra in it.
Boat dry about 1100, motor about 220,Don't forget battery and gas.
Let us know what you find.

 

[LV2FISH4CATS]

Re: Propper Props???

Thanks for all the info,
I will look into everything listed and try the motor problems first. I do have and OEM shop manual made by clymer. I will look inot the plugs and carbs... I will read more on the link and sync. It is nice to get info on where one might start.

The speed i was reading was from the GPS on my locator. I will check and probably replace the tack. It is factory and 33 years old.

Will give reports on what I find.
Thanks

 

[Tacklewasher]

Re: Propper Props???

Thanks for all the info,
I will look into everything listed and try the motor problems first. I do have and OEM shop manual made by clymer. I will look inot the plugs and carbs... I will read more on the link and sync. It is nice to get info on where one might start.

The speed i was reading was from the GPS on my locator. I will check and probably replace the tack. It is factory and 33 years old.

Will give reports on what I find.
Thanks

By OEM I meant OMC. The Clymers are not that good as they try to cover too many motors. But I do think they go through the link-n-sync procedure fine.

On the tach. See if there is a "pole" setting on the back. It should be set to 6. Sometimes people think it should be set to the number of cylinders and switch the setting, but it needs to be on 6 for these motors.

I can tell by listening if I'm on 3 or 4 cylinders as I had one coil that kept giving me trouble. My old hood was deformed and if I wasn't real careful putting it on, it would pull off the plug wire. Replaced the hood to solve that one. With the motor idling (on muffs, always on muffs) pull one wire off at a time. If the motor loses rpm, put the wire back and move on. If it doesn't lose rpm, you found a dead cylinder.

Then I would do a compression check. Not to worried about the numbers, just that all 4 are close to each other. Mine are all around 100 psi, but the actual number can vary by the tester.

Assuming compression is good, I'd look into the carbs. I rebuilt mine and it made a bit of a difference, but I'd walk through the link-n-sync first to be sure your timing and carbs are set up right. There is a procedure around here somewhere on how to set the timing so it is close without being on a lake.

Think that's enough to keep you busy.

 

[Tacklewasher]

Re: Propper Props???

The Tyee appears to be fairly light at a about 1100 lbs.A 140 should easily push it to 40+ And get smartly on plane. I would guess the right prop size at 17 to19"

So would I.