At it again! 40 hp 1990 yamaha precision blend

This time I’m looking for some prop suggestions from the wizards in here. I noticed once I pulled out the boat this last week and garaged it for the week while I’m away I was washing it down and noticed a blade on the prop looked a little wonky. Upon closer inspection I realized that there was a good ding that I could possibly hammer out…only to see the next blade was much worse and had a small crack as if it had caught a stone while beaching. (Don’t think I did it, but not going to deny it, just don’t remember hitting anything) So the prop wars begin. It’s a 3 blade on it now…I like the hole shot so far, gets right up, could use a little more speed but nothing crazy. It’s a 13′ classic whaler so it moves right along with the 40. Suggestions?? 14° perhaps? I want another aluminum prop, case I do actually knick something. Left hand rotation, 40 hp, 13′ whaler, im thinking as steep as I want to get is 14°. Thoughts? (And prayers?) Thanks in advance

What prop do you have now?
If you want to go faster you just increase pitch.
You always sacrifice with props, higher top end usually results in worse hole shot.

I just downsized my prop this past week and sent two others in for repair.

Don’t run dinged props, they’ll wear out more expensive things in your motor.
Your motor should NOT vibrate from a prop. Vibrations at HIGH rpms throw bearings and reek havoc on lower units. Props are low cost in comparison to those repairs.

I don’t know what 13 or 14 degrees means.

Props are specified by the diameter (first number) and the second number is pitch.
Diameter is the diameter of the prop if you drew a circle around the blades.
Pitch is the amount of forward distance it would travel in 1 rotation through soft media.

Increasing diameter increases your flow (You may not be able to go larger diameter).
Increasing pitch increases your flow. Example a 14 pitch is less than a 16 pitch as far as how much water is being pushed.

Not 100% sure what the prop is now…pretty old and worn. I was hoping that the specs like model make and year would help me out on just starting fresh.

I would just get another the same as you have now if you like it. You not going to get anymore speed out of a 40hp motor. The hole shot would be my main concern.

The specs on the prop should be cast right in, so they’ll be there.
Bring it into a marine shop and they’ll look it over and make a recommendation based on what that prop is and what you’d like your boat to do differently.

Someone may be able to get you going off your boat specs, but they haven’t a clue what you have right now. If i had to guess on a scale of 1-5 with 1 being the best hole shot and lowest top end and 5 being slowest holeshot and best top end you’re probably a 3. IMO that is propped right for most situations. It is the user who would rather edge toward the 1 or the 5 based on their typical usage.

I’d guess your boat is at max HP so you’ll enjoy good holeshot and good top end with that middle of the road prop. Can probably edge up or down and you won’t notice a ton of difference but you may exceed max HP if you prop down.

After a good bit of gas going through it and finding an oem prop , I think that what I have is top notch. Now if I can just get the idle right I think it will almost be perfect…til it needs a tune up again. I’ve taken care in trying o chase the problem from the cheapest route. First thing was check the gas for water in the separator and polishing filter, little dirty, no water. Next was changing out the old primer bulb and adjacent lines to the outboard…still sputtering at idle. Next I checked the plugs, which were a little fouled out but still “2 strokey”, so I out new plugs in, stuck it in a water barrel and let it run with some k100 in fresh gas… , still sputtering, but not AS bad… , so I took that air handler off the front of the triple carb body and noticed some condensation on the inside of the intakes, wiped it cleaned with a fresh blue shop cloth, sprayed some ether in there to dry it up, fired it up with no air handler box on there to see it breath unrestricted, still sputter a little. so I let it run for about 15 minutes with the fresh gas and shut it off, only to see more build up of condensation on the intakes and butterflies. What gives?? Where is that moisture coming from and is it why my yamo is still sputtering at low idle?

Have you put a can of seafoam in a gallon of gas(and oil) and run it?

moisture at the carb entrance is normal, the high velocity air going through the carb cools the air and the moisture will settle out and form droplets that you are seeing.

as far as the crappy idle, it could be as simple as the carb idle mix screws need adjusted ( they are sealed and you have to know how to go about it ), however, before I would mess with those I would perform a compression test and a spark quality test.

here is a simple test you can run, you will need a spare plug.
leave all spark plugs installed, install the spare plug into one of the spark plug wires and ground it.
start the engine and see how well it runs on the rest of the cylinders, do this one plug at a time until you find the cylinder that least affects the idle.

once you find the cylinder that is providing the least amount of change you have found which one is having a problem.
swap that plug out with a new one, if you still dont find a change do this next.
swap out that coil with another cylinders coil, repeat the first test above.
if the problem follows the coil you have a bad coil.
if no change is found then you have a fuel issue with that cylinder.
hope that makes sense.

The first thing I did when I bought it was run seafood through it…just an old southern habit

Aye aye aye….im glad the droplets are…”normal”, I have just yesterday taken all plugs and replaced, the only thing I haven’t really done is check the coils, judging from the zip ties on the foot of the boots going on the plugs , I would say they are due for a change, and I’m not too poor to buy three new ones. Mechanics around here are mad busy and will take till the season slows before I could actually find one to check internals and such.. I was hoping I could adjust some carb stuff but was thinking it was a fuel issue. I ran about 4 gallons of high test though it today with decent amount of load and it bogged down a couple of times. Mind you I had also added some k100 to the fuel to hopefully burn out any water in the system…which is exactly what it felt like…it would run run run for about a half hour, then it bogged down once…I idled it back down, waited a second or two, then opened it back up and it blew out whatever was clogging it (I think)…then is did the same thing one the way back to the ramp, about halfway back..(which is ocean boys…ocean) . Same end result, got to the slick water and had WOT for a good 2 minutes, ram like a bat out of hell. I almost feel like this thing is set to pop just barely before it stalls like a car with a 3/4 race cam in it. It has plenty of power…just sputters like stuttering Stanley at idle, especially after it’s been running hard…. Iowaboy didn’t you say once you could get me parts? I’ll be looking for 3 new coils w/wire (because I believe they’re hardwired). I appreciate the swap out coil trick. I will pull it into the garage tonight and check these new plugs I put in and see if they’re fouled at all. I haven’t given up yet, besides, to fit a new 4 stroke 40hp on here is about 9k with the rigging…

Send me your model and serial number in a PM.
I will find the parts for you and send you the link to where you can get them.

My four stroke did that with a loose battery terminal. It was not the first thing I looked at.

Iowaboy will get you going on the fuel/electrical issue.

As far as propping it,I hope you have a tachometer?No matter what prop you have,it is critical to be in the recommended RPM range at WOT.So if that model is 5000 RPMs,I would shoot for around 5200.Better to rev 2-strokes than lug them.I have seen too many overprop boats,slow holeshot,can’t properly plane boat by thinking a larger pitch would go faster.It’s a lot more wear on engine and wasted fuel by lugging it.

I found a woman who’s husband has ran a prop shop up here for the better part of 50 years. She was dubbed the prop-momma, she took one look at my prop and had it figured in about 30 seconds…

What did prop-momma say?

She said,” yamaha?”
I said,”yes”
She said,”40 horse?”
I said,” right again”
She said,” I’ll be right back I have three oem props in the box”
Came back like 5 minutes later with 2 and she said,”how’s the hole shot?”
I said good.
She said ,”how’s the top end”
I said,” gets up on plane and wants to liftoff”
She said,”here, you want this one, same as yours, just new, shiny, and white, that’ll be 159.99″
I said, “can I have a new cotter pin too?”
She smiles and said,”I’ll throw in a pin for free”

—the legend of prop momma continues

prop momma sits at the TOP of which mountain?

They call it Monahan’s Mountain on the foothills of Weymouth… legend has it sometimes late at night you can hear a 2 stroke rapping out between swells in the fog.