poor performing yamaha 4 stroke

astrobass1 · Apr 2, 2012

Hi all I just recently purchased a 2009 Skeeter SX180 with a 2009 Yamaha 115. 4 stroke .
We took it to the lake this weekend lightly loaded 1/2 tank of fresh fuel added the ring seal as Yamaha suggested motor runs flawless nice and quiet (other than the belt squealing at idle) It took forever to get on plane after on plane and trimmed out all she would do is 41 GPS MPH at 6000 Wot .Stainless original prop I guess. I've seen on many forums including this one this setup should run in the mid to high 50s fully loaded. Any help'would be appreciated.

Philster · Apr 2, 2012

Re: poor performing yamaha 4 stroke

Well, you're at the max RPM rating I believe. Not familiar with many 115 HP o/b's that would run an 18' boat into the high 50's fully loaded.

Are you sure it isn't the 150 that will run to 50 MPH?

astrobass1 · Apr 2, 2012

Re: poor performing yamaha 4 stroke

Even the dealership said it should be in the mid to high 50 s. I also have a 1996 18 foot astro with a 115 merc 2 stroke (loaded all factory setup) it'll run 52 GPS MPH easy I think someone might have swapped the props at the dealership. It looks a little small for the motor no markings are seen without taking it off
Any idea what should be on there? And could I go up a pitch?

steelespike · Apr 2, 2012

Re: poor performing yamaha 4 stroke

I agree. I think you got into the 150 performance reports. You didn't say what prop you are running.
We need prop size and material.Size will appear near the bass of the blades or under the prop nut.We can probably improve hole shot
wot speed would depend on the present prop.

Maclin · Apr 2, 2012

Re: poor performing yamaha 4 stroke

Going up in pitch now will make the "forever to plane" time even longer.

"Forever to plane" AND low top speed at 6000rpm are at opposite ends of the problem scale.

Usually low top speed at full engine rated top rpm means underpropped (pitch too low). Planing times are usually fast in this scenario.
Slow planing times usually indicate a boat is over propped (pitch too high). This can also mean the drive trim is not being fully utilized.

To fully analyze your situation the drive ratio and prop pitch are needed along with the RPM and MPH at WOT.

Also may need to weigh the boat to make sure it is not carrying around some excess water (or other) weight.

Some new-to-me in-laws bought a brand new fish/ski type boat last year and the live wells were not plumbed correctly so it took on water the whole time and the automatic bilge pump was being outpaced slightly. They were very unhappy with the performance of their boat until they got it back to a regional dealer and got it all fixed up.

Just sayin' that it pays to check everything.

Philster · Apr 2, 2012

Re: poor performing yamaha 4 stroke

If you are hitting the rev limiter, then you could go up in pitch and get close to 47-50 MPH out of her.

What's on there now... a 19p ?

If the rev limiter kicks in at a higher RPM and she's hitting her own wall, then going up in pitch will knock off some RPM and return about the same speed.

Philster · Apr 2, 2012

Re: poor performing yamaha 4 stroke

astrobass1 said:
Even the dealership said it should be in the mid to high 50 s. I also have a 1996 18 foot astro with a 115 merc 2 stroke (loaded all factory setup) it'll run 52 GPS MPH easy I think someone might have swapped the props at the dealership. It looks a little small for the motor no markings are seen without taking it off
Any idea what should be on there? And could I go up a pitch?

You realize one boat could be lighter by nature, and a 2-stroker can sometimes outgun a 4-stroker of the same HP? Most often, it'll be in mid-range, but some time-tested 2-strokers have great top ends above and beyond what a more fuel conscious and emmisions conscious 4-stroker might do.

steelespike · Apr 2, 2012

Re: poor performing yamaha 4 stroke

I went very quickly through 5 pages of Yamaha tests one 115 boat reached 50 the rest were roughly around 40.
The Skeeters ZX180 47 @ 6000 w/19" ss prop, TZX180 45.5 @ 5850,19" ss prop.

( 150 hp) ZX180 58.6 @5700 23" ss prop.
I do wonder what belt they run and why its squealing probably just loose but could be something dragging.

astrobass1 · Apr 2, 2012

Re: poor performing yamaha 4 stroke

Philster said:
You realize one boat could be lighter by nature, and a 2-stroker can sometimes outgun a 4-stroker of the same HP? Most often, it'll be in mid-range, but some time-tested 2-strokers have great top ends above and beyond what a more fuel conscious and emmisions conscious 4-stroker might do.

I'm going to take prop off tonight and see what pitch it is the boat weighs 1800 lb dry my astro weighs 2400 lbs. Dry
Not hitting the rev limiter at all just feels like not enough boat out of the water. Jack plate? Thanks guys I'll return tonight

steelespike · Apr 2, 2012

Re: poor performing yamaha 4 stroke

Does the boat respond to up trim?Let us know size and material.If you can't tell material; ss is magnetic
Full up weight was 2700 on both with 115 engine.

astrobass1 · Apr 2, 2012

Re: poor performing yamaha 4 stroke

Took prop off tonight is says. y-09. Lt-17-K
It looks small to me, I called Texas (Skeeter) and the tech support says Yamaha stamps prop under prop nut this is under the back.prop looks thin (like a cheap one) ,it is stainless but is rusting in the flexes lightly .

Philster · Apr 2, 2012

Re: poor performing yamaha 4 stroke

I don't see any way based on the info provided you can jump 10-15 MPH with any prop change at this point (the opening post mentions mid-50's.)

I could see squeaking out 45-46 with a good combo of RPM/Prop/Trim.

astrobass1 · Apr 2, 2012

Re: poor performing yamaha 4 stroke

Let me say I'm not trying to be a speed demon I am merely a perfectionist. I paid 17,000 for a 2009 boat well worth it but just making sure it is as close to factory as possible, Also so the mentality is set, I have been a boat nut since 1990,First owned was a 1986 Dixie superskier 299 .,converted exhaust above water level,trim tabs,Michigan Wheel perforated 27 deg.brass 4 blade prop,at the same time had a 1988 centurion bow rider competition ski boat , I have had 4 boats since then, Now I,m old I have a Bass boat to piddle, just want it to be right...
Thanks for all the help

astrobass1 · Apr 2, 2012

Re: poor performing yamaha 4 stroke

Maybe I guess its all okay and. I just purchased a slower boat,just making sure its right

steelespike · Apr 3, 2012

Re: poor performing yamaha 4 stroke

You can probably get the 45 to 47 I reported for the Skeeters thats assuming the boat hasn't been modified.more to follow The skeeters I reported on were running Yamaha PRO 19" ss props.
The ZX180 at 47 6000rpm The TZX180 at 45.5 @ 5850. These came right out of the Yamaha performance bulletins. perhaps a PRO 19 will solve your problem. Though I wonder if you can get 6000 out of it.

Philster · Apr 3, 2012

Re: poor performing yamaha 4 stroke

astrobass1 said:
Maybe I guess its all okay and. I just purchased a slower boat,just making sure its right

No, you are doing right, but if you have a boat in good condition and a prop that runs that engine up to 6000 RPM at low 40's, anyone chiming in is sort of stuck to get more out of her.

The things that would slow a boat down would reveal themselves somewhere. If you are spinning a given prop and the engine hits 6000 RPM @ low 40's speed, the only way to go faster is to get more power or a lighter boat, which you'd take advantage of with a higher pitch prop. If the power output of the engine is to spec and boat checks in to spec on a scale, then it's easy to say you can only get a couple MPH out of her with tons of tweaking.

Nothing seems totally out of whack for a 115 here, but the final sleep-at-night sanity check comes from weighing the boat and ensuring the motor is up to snuff. That's really it.

steelespike · Apr 3, 2012

Re: poor performing yamaha 4 stroke

Philster,A couple of posts up he's running a 17" ss and I don't think a Yammy PRO.
The skeeters that were running 45/47 are running a PRO 19 ss.Whether the PRO will let the motor run up to
6000 would depend on the props action on the boat.Seems unlikely.

Philster · Apr 3, 2012

Re: poor performing yamaha 4 stroke

Oh, I wasn't suggesting a bigger prop. Essentially saying where he is at is just about full potential unless he gets more HP or a lighter boat. With the given engine/boat, there not much else to do.

steelespike · Apr 3, 2012

Re: poor performing yamaha 4 stroke

I wasn't suggesting that.
it seems to me assuming his and the tested Skeeters are similar his should do well with a PRO 19 as well.
If it doesn't there may be other issues.
Just did a quick calculation The Pro 19 assuming 5600 and 6% slip would do about 44 mph.
Of course may slow hole shot further. I guess thats where smart tabs come in.?

Philster · Apr 3, 2012

Re: poor performing yamaha 4 stroke

Oh, I see.

Tabs: Can't hurt, but how about a vented prop, too?

poor performing yamaha 4 stroke

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