please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinrude)

[Can'tFishEnough]

I'm pretty new to boats - other than going with others to fish/ski/tube etc... but now that i have a little fishing boat - 14ft texas maid with 1992 15hp Evinrude I'm trying to learn what options might give best performance increase for lowest cost and least amount of "hole drilling", time, or $. (sorry in advance for a long post that may still be missing critical info... but I've tried to be as specific as possible for my situation).

Background setup:
The boat is what I guess you would call a semi-V bottom - it has a deep V at the bow and is nearly flat or just slightly rounded at the stern. The transom is 16inches tall.

The motor seems to have originally been a Long shaft motor indicated by the L in the model # but it when measured it is 17in from the clamp at the top of the transom to the AV plate. It has manual trim (the type with the 5 holes and a pin to adjust it) The prop is marked as 9.3x9.

I have raised the motor up 3/4 of an inch with a small wood spacer under the screw clamp brackets and seem to have better performance under my typical load (about 245-260 # toward stern - me, 6 gal gas tank usually about 1/2 to 3/4 full as far forward as hose will go, and some gear -not including motor or trolling motor... and another person usually my wife + trolling battery anchor/small cooler maybe a few other items at the bow that are probably around 220-235). we cruise at about 18 mph on the gps with the motor on the middle trim hole. (before raising 3/4 inch were cruising around 17 mph). Problem is that when I add a heavier guy in the front maybe
someone around 250 or so plus the 60-70 lbs of battery and anchor etc we just plow through the water... at maybe 12 mph or very best with the wind at our back 14 mph in flat water.

What I am sure of is that I can't afford a 20 or 25 hp motor this season... maybe in the fall I can find a good used one on craigslist or something... but it's not in the cards for now.
(Will be ordering a tiny tach I may be able to get it in this weekend.)

SO here is what I'm unsure of at this time:

-- should I investigate trim tabs as a possible way to stabilize the boat and add some lift to the back?

-- Do I look in to new props? I've seen some SOLAS AMITA 3 on ebay with all the different pitch sizes that would probably be in the budget.

-- have current prop modified: I talked with one prop shop today that said he could cup the blades on the prop I have and that would probably fix the problem ( a little more top end speed and less ventilation or cavitation / he said it would be about $25 - my cheapest option: BUT would it really help???).

-- should I look into hydrofoils (like the permatrim) that might not cause too much extra drag to decrease top end but keep water actual around the prop so it doesn't cavitate and start slipping whereby possibly increasing top end a bit...

Please be gentle on the replies - I'm trying to learn here & make a wise decision, but with all the different options and opinions, I'm unclear what I should try first.

 

[rallyart]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

You describe the boat as working well and getting on plane with you and your wife. When you add another 300# or so it no longer gets on plane.
That sounds like you are just underpowered with the heavy load and push too much water to get up to speed. Tabs or a foil won't help get the boat our of the water further. If the prop is cavitating a change to it might fix it some. You'll hear if the prop is cavitating when your load is high.

 

[Can'tFishEnough]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

ok, yeah I agree it's probably under powered... but I'm not totally sure I'm getting on plane with just two people (me and wife), but I think that it is close... (not really enough experience to know exactly how it's supposed to act and feel and all that). BUT what I meant was not adding a third person but exchanging her for a guy who may weigh 100-120# more (so still 2 adults maybe a 40# kid in the middle either way but that doesn't seem to make much of a difference speed wise). Just trying to find out options, opinions on what might help before spending a lot of money and finding out that it just needs a bigger motor plain and simple... I believe that it is rated for 30 hp but would not swear to that being that it was built in 1958 (before the plates were put in that said the ratings). I hear the prop cavitating a lot especially when making turns that are very sharp. with the motor raised 3/4 inch or not it's about the same - I would just like to get a little more top end speed - it may be that I need put the battery in the middle or back when persons over 200# are in the front - I haven't tried that yet...

So far I have not run it with 3 adults in the boat in any configuration -so no numbers on that- I think at that point I'd just have to have them holding helium balloons or something... but I may do that in the future but mostly for some trolling type fishing on some small waters - or where we can launch close to where we want to fish.


I guess one of my main questions is if the prop is cavitating a lot does it need to be higher pitch to push better without spinning so fast, or lower pitch - but then I worry it will just over rev without getting anywhere... is my thinking off? (it's likely I have it backwards which is why I'm trying to ask before shelling out $).

Thanks

 

[Home Cookin']

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

I think you are overthinking it. A 15 on a 14' tinnie is about right. The discussions around here are for bigger rigs.

If you are frequently carrying loads and don't mind too much speed when alone, go up to a 25. but foils are a waste, trim tabs are for bigger boats, props may make some difference but factor in the cost, it may not be worth it.

3 people in a 14' boat is not likely to do much planing. One trick to help get up on a plane is to run over shallow water. Play with shifting your passengers around, too.

Enjoy what you have.

 

[steelespike]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

When you get your tach you need to empty the boat except for required equipment safety,gas etc.
Remind us of the prop size,and do some test runs with just you.With careful trim and weight placement a healthy 15 should be capable of speeds approaching 25 mph.on your 14.
Your hole shot and max rpm and speed will help us evaluate your setup and motor.
Anothewr way to go to improve load performance is a bigger boat another bare bones big 15 or 16 ft utility.at least 15ft or 16ft centerline length nice and wide.This will get a load up better.
And will feel like the Queen Mary compared to your 14.

 

[SparkieBoat]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

a 15 on a 14 alum is ok but I have found it to be a little slow for my taste even with a light load. a 25 is what I prefer. I can get on a plane and cruise 25 MPH fully loaded easily.

 

[steelespike]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

I agree the 25 will do a nice job.We had an old 25 gale on our 18ft Crestliner bare bones utility
and it planed easily with 6 aboard.With no special setup or prop selection.
Unfortunately the 25 isn't in his imeadiate future.If he does go to a 25 on the 14 he will still have a smallish boat that will struggle with a load and feel cramped on trhe water.
I don't know how a used 25 price compares to used full sized 15 or 16 base utility.But I think a good healthy 15 will serve well on a bigger utility.

 

[Can'tFishEnough]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

thanks for the thoughts... I have a tach on now and will be going out on a little fishing excursion in the morning. So at least I'll have an idea of what the engine is doing (will have to wait on the "empty" boat test... as I just haven't had time to go do that --- I'm a little confused as to why I wouldn't test it "loaded in the most typical fashion"??
Wouldn't I want to set it for best performance as it is most normally used?

Well either way this one will be me and 2 kids up front (sitting on the bench behind the battery), but I should be able to at least get some tach #s and trim settings (something else I'm not always intuitive on for different loads (remember it's a manual trim - I usually start in the middle - go down one if worse go up one - and usually end up back in the middle or one up - only with a heavy front seat passenger have i ever went one down and that was mostly just to not get so wet in the chop that day - it was a bit smoother, but I think we were going slower too (didn't have the gps with me that day).)

I would LOVE to upgrade boats and motors - I think there is no question about that, but for now - $ and wife say you got this one... be happy - SOOO, I was just hoping that for less than $100 or so I could get a little better performance out of it with a prop (foil, etc. as stated in original post).

For now going from a 12ft flat bottom with a squirly 4hp that was older than I am... this boat does feel pretty big... it gets 2 adults and 2 kids out on the water and away from the computer/video/etc. and sometimes we catch some fish in the process
Will try to take good notes and report back in a day or so.

HAPPY 4th!!! hope you're all out on the water in the morning too (but if you are reading this - thanks for your comments and help).

(oh I may have a line on a 20 hp from craigslist that "needs some minor work" (you know how that can go) but if it works out I may be able to upgrade that way... just need to "actually see" the thing and get some numbers to search online for cost of said needed parts/ find out what year/ and see if s/n shows up in state database, etc. before spending $ and time on it and finding out i got snowed...)

would 20hp really be that much better than 15? I was originally trying to stalk a good deal on a running 25 hp but most of them now in my area are only being sold with the boats attached

 

[Can'tFishEnough]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

Your hole shot and max rpm and speed will help us evaluate your setup and motor.

I'm not exactly sure how to measure the holeshot...
RPM I can do now, and top speed is possible with gps...

In case it actually makes a difference I'll add this... with normal load (fuel battery, trolling motor, outboard, a few safety things and a small bit of fishing gear and just me I was getting about 21mph on the gps after moving the motor up the 3/4 inch, but when I turned a little too sharp I just lost all power until I went to idle for a bit and then it slowly climbed back up... I thought I fried it... but now after reading a bit more I think it was cavitation/ventilation and I had to let the bubbles all get out of the way before it would grab again. (before raising motor I had never gotten above 19 on gps but only was out alone once or twice and I don't really remember wind/water condition etc... just knew that I was "maxed on the gps trip gauge" over where it had ever been before).

 

[steelespike]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

21 is a respectable speed considering no special setup has been done yet.If your prop is a little worn and or dinged up it may be sensitive to venting a little.With your tach you can get an idea where your rpm is with that load. At 21 the boat is planed pretty good anything slower it is more difficult to select a prop because the boat hasn't planed comepletely and the rpm would be artificially low.I think you can see that a lightly loaded boat will give a more accurate indication of the setup and actual rpm.We'll help figure the prop its a little different with smaller motors but still the same idea.
Problem is when your lighter you may over rev so you need to be aware and
control the rpm.Motor is rated at 7,000.
It would be interesting to know the centerline length of your boat and the widest part.

 

[Can'tFishEnough]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

Thanks for the comments: I just thought I would chime in again and give a quick update.

I went ahead and sold the hydrofoils I bought as they wouldn't really fit the cavitation plate on my motor without some modifications anyway (like moving the anode). Anyway, I took the prop off and took it to a prop shop and asked them for advice. They informed me that the prop was indeed stainless and it would be better to just cup the edges rather than replace it & so that it could ride higher in the water (for less drag & for less cavitation-- though probably more likely ventilation problems). I couldn't tell you exactly the amount of cupping they put in but it may be about 1/4 inch of turn at an inch and a half or so radius.

After having the prop cupped I was able to raise the motor about 1.5 inches. Now it seems that for minimal loads (one adult + gear) I get a lot better performance. At most of the middle trim settings I couldn't even tell a difference - I think it topped out about 22 mph after getting going. Not much increase in speed, but it does have a lot better performance in choppy water and when turning.

Holeshot is still pretty much non-existent - but I have no need to throw everyone out when throttling up anyway . It seems to hold it's own with me and one other (self, wife, 2 kids) or even me and two lighter adults (with wife & sister-in-law) and a kid or two. The trim settings don't seem to change things much at that point either. So I just put it in the middle and we go.
With 3 adults (all 3 guys) and a kid it's pretty much a barge... but that's to be expected I guess with only 15 hp.

at the medium load (or normal for me - 2 adults and a kid or two) i get RPMs right around 5000 going full out. I don't know if the cheep tach or engine flucuiates but it tends to read between 4600 and 5500 as we're crusing along. Obviously lower for more weight. It was maxing out at about 5000-5200 with 3 guys this last weekend. It's been awhile now, but I think with just me it was running around 5500 or a little more, but at that point the sensor was picking up both spark plugs and I was having to divide in half. (I thought I had it set for 4 cycle engine but figured out the two plug wires were just too close together).

Oh, and in response to some earlier questions, length is nearly exactly 14ft from stern to tip or bow, and width (Beam I guess) is around 58-60 inches at the widest part (it's been a bit since I measured) and tails off to a bit thinner in the stern - maybe 45-50 inches. Transom is 16 inches and bow probably sits about 3 feet from bottom of V when on the trailer.

Anyway, thanks again (even thought it's been a while).
I had prop done soon after this tread was started, but wasn't able to use boat much for the last year or so. Now I've been able to start getting it back out on the water, it reminded me that I should give an update. (still hoping to find a decent 20 or 25 hp engine to put on, but have to save up some more pennies for that... )

 

[dazk14]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

1st- That's way to much reading. Your engine isn't developing full power at 5000 rpm. It needs to run up to 6250 to get all 15hp. You're probably getting ~12 at 5000.

As I recall, the full throttle RPM range is 5500-7000, so it needs to rev to get it's full power. That's good news for you.

Get a price to remove some pitch from that prop. Leave the cup. an 1" decrease in pitch will gain quite a bit of rpm's, but I need to see some data. Ask them if the prop now has single or double cupping, although that's not an exact numerical term.

Post a grid of approximate weight, speed, and rpm.

Do you have any "before cupping" speed, rpm, load data.

Properly setup, that 15 should be suitable for your needs. We just need to get all the power to water. Those are very nice motors, with tons of used parts available and very good resale value. Up to $750 for a nice one.

Edit: a more accurate word than "suitable", is probably "functional", but again there was so much written, let's see the Cliff Notes version.

 

[steelespike]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

From your dimensions I'm guessing your boat capacity is probably 700-800 lbs I couldn't make head or tail how
much total weight you have aboard. Assuming trolling motor and battery,yourself 240 motor 80 lbs Boat 200, 6 gallons of gas and tank 40lbs. I figure your around 700 lbs. Have you made any additions to the boat?like a floor or casting deck live well?
I think we can see not much room for brilliant performance.
If you were to do a test run; you alone and no gear we may be able to tell better how well your setup works.
Remind us of your light load weight.
On the tach you need to use the bottom plug wire and get the wire outside the cowl as soon as possible.

 

[Can'tFishEnough]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

From your dimensions I'm guessing your boat capacity is probably 700-800 lbs I couldn't make head or tail how
much total weight you have aboard. Assuming trolling motor and battery,yourself 240 motor 80 lbs Boat 200, 6 gallons of gas and tank 40lbs. I figure your around 700 lbs. Have you made any additions to the boat?like a floor or casting deck live well?
I think we can see not much room for brilliant performance.
If you were to do a test run; you alone and no gear we may be able to tell better how well your setup works.
Remind us of your light load weight.
On the tach you need to use the bottom plug wire and get the wire outside the cowl as soon as possible.

I know, I'm not expecting "brilliant performance" but do appreciate you all helping me get what I can out of what I have - Thanks for that!!!

From what I found online a while back (some old scans of Texas Maid boat data years '58-'61), it looks like the Standard/Utility model is rated for 1000 lbs of passenger load and boat itself weighs between 190 and 212 (the '57 & 58 data shows passenger capacity as 6 while the later years show 1000 (I am assuming persons & pounds respectively).

Title says it's a '58, but the previous owner's daughter was selling it and she said they really didn't know the year but needed one for the title.
(3 bench seats + mine has a very small "deck" type seat at the bow but it's not really for standing on).

I don't know if this will help, but here is the Typical load with no people:
Note: No additions other than a set of lights, 4 clamp on swivel seats, & the "junk in the bottom" -
battery,
6 gal gas tank,
2 anchors (1 light self releasing type the other more of a heavy chain we've tried to use to control "drifting"),
cast net,
trolling motor,
regular motor,
medium size tackle box or two like the Plano 2 or 3 tray type,
couple poles,
couple oars/paddles
(usually a small cooler
and about a 3.5 gallon bucket for a bait "live well" but that hasn't really been used too much lately).

Figure the ladies I mentioned around 140-ish, and they guys about 200-250, kids about 45-50

Remind us of your light load weight.

The lightest load I've run is probably me (about 200#s) and 3 gallons of gas and most of the other "junk/equipment" listed above. That was about 2 yrs ago when I was taking the boat from the ramp about 600 yards around to a state park to pick up the wife and kids. Otherwise it's always been me and at least one other adult or two kids...

If you were to do a test run; you alone and no gear we may be able to tell better how well your setup works.

I don't really have a lot of "empty load data" since it's a bit of a chore to get it to the lake with the family (and sometimes in-laws) and if its in the water we're trying to get somewhere to fish - I don't really have as much time to just do "testing", but maybe this spring I'll have more chances to take it out with different configurations. I do greatly appreciate the comments even with my limited amount of data - I know that's a short fall on my part and will see if I can get better.

On the tach you need to use the bottom plug wire and get the wire outside the cowl as soon as possible.

I do have the tach on the bottom plug now - it was on the top, and near both wires... so all that data's probably pretty screwed up anyway... I will take better notes from here on and see about a way to get the wire out of the cowling sooner. Now it just runs low around the side of the engine to the handle.

Will answer more later tonight if I can.

 

[Can'tFishEnough]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

1st- That's way to much reading.

Sorry it was long... I was trying to get all the info in I could for the follow up...
And 1st to you, Thank you for getting through it and replying with your thoughts! I will try to get new and better data for you. The "before cupping" results were pretty much the same I was just getting a lot of ventilation in the prop when turning (even in pretty wide turns) after I raised the motor an inch.

I'll try to go back by the prop shop and see if they can help me answer you a little better. Thanks for the "hope" that I still can get more out of this one.

Would the mixture have anything to do with the max rpm? I know it does on aircraft engines - but those are 4 cycle... but as you lean it out you get higher RPM but can burn up the valves...

I suspect that I may be running it a little rich or with too much oil also (I think I used 1:50 ratio- I'll check later) ... At the end of the last trip it was acting like the plugs were fouled a bit. I'll clean them up and see if I can lean it out some too. Just hesitant to tear it up or something. I don't really know how to use the mixture setting on the outboard for best results... I just set it in the middle for now.

 

[Sea Rider]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

Wrap 3-4 turns of red cable around any spark plug wire + ground. Assume you have purchased the programmable firing sequence model, if being the old model probably will read half or double at wot, if so, useless.

What you need to do is go for a wot spin with you alone and lightly loaded boat, check achieved wot rpm. That engine revs at 5000-6000 rpm at wot, check if inside those numbers, the higher the better.

Place wife and gear, go for other trial test, check achieved max rpm on that run, definitely will read much less rpm that previous run, you could be entering the lugging zone which is dangerous, too much stress on pistons and crankshaft.

A 15 HP is a poor performer for that heavily loaded size boat, you're definitely way underpowered. If going with 3 and mentioned total load is a must, will need to install a prop pitch that gives at least 5500 rpm at wot, bear in mind that as soon third mate steps out of the combo rpm will be increased accordingly. If you select a prop that gives full 6 K with 3, when third boaters steps out your engine will be over revving.

Happy Boating

 

[jestor68]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

Sea Rider, you're thinking of the 9.9 for 5K-6K rpm range. The 15 has a range of 5500-7000 rpm, as previously mentioned.

Let's not forget that we're dealing with a 22 year old motor here. It obviously can't handle the pitch that's on there.

Edit: I'm beginning to think that tach is off, because some slip calculations indicate that your motor might be turning over 6K rpm using realistic slip numbers with a 9-10 pitch prop.

 

[Can'tFishEnough]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

Wrap 3-4 turns of red cable around any spark plug wire + ground. Assume you have purchased the programmable firing sequence model, if being the old model probably will read half or double at wot, if so, useless.

What you need to do is go for a wot spin with you alone and lightly loaded boat, check achieved wot rpm. That engine revs at 5000-6000 rpm at wot, check if inside those numbers, the higher the better.

Thanks. I'll see what I can do next time I get a chance to go to the lake.

The tach I have is a knock off tinytach brand I got off of e-bay. I actually had one first with the 2 wires like you mentioned but I smashed it taking the motor off the boat to drive a pretty long distance home from a camping trip. The new one only has one wire. The merchant (same guy on ebay) said that was the new one they were getting and didn't have any more of the others. It is programable for 2 or 4 cycle and maybe 4 cycle that fires every other stroke (he said some lawn mowers do that - I'm not sure if that is different than regular 2 cycle reading...)

I'm also trying to see what all is "excess" that can be taken out (or not put in) for future trips. I just have a little bit of a boy scout "be prepared" mentality and not having a lot of experience on the water, I try to have something for any situation I'm in - fishing or emergency... problem is I don't really get a chance to go out on the same lake day in day out enough to know what to take or not take etc. Also some of the lakes here in N. TX can get a bit choppy for this boat if the wind picks up even a little, which was really one of my main problems before - the cupping has helped that quite a bit.

I'm learning. Thanks - I'll see what I can do I can't recall what the RPM was was with just me - and with a different tach set up and wire in a different place now all my old data is probably not valid any longer.

As stated to dazk14, I'll talk to the prop shop and see what they can do or what they suggest. I just don't have a whole lot of cash to throw into trial and error... it may be a week or 2 before I can get by there.

 

[Can'tFishEnough]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

Let's not forget that we're dealing with a 22 year old motor here. It obviously can't handle the pitch that's on there.

Jestor68, so you think it for sure needs a smaller prop? or needs to be re-pitched (if that's the right term)?

The way the guy had it set up the cavitation plate was about 3 inches below the water line and 1.5 below the transom when I got it. I think he just bought a motor that he could afford and went with it. probably wasn't too worried about performance.
I for sure don't want to blow this one up... now you have me a bit worried... can you expound a bit on your comment.
(obviously pending a bit more testing...)

My main goal of this tread:

I want it to run well with at least two adults and two kids. Say 500 lbs of passengers + the trolling motor/battery/main motor/fuel and the clamp on seats.
I'm willing to start leaving some of the rest of the clutter - maybe get a smaller fuel tank also (or not fill it as full).
Eventually, I'm still hoping to find a half way decent 20 hp or maybe 25 hp motor that I can afford or trade for.

 

[jestor68]

Re: please help sort out options... prop, hydrofoil, trim tabs, or other? (15hp Evinr

Can your budget handle $77.99 for a Solas Amita 9 pitch, 4 bade prop?