Tried 2 props, what do I try next?

Hello Everybody!

I have a small console-boat called Yamarin which I think is unknown in the US. It is 17'8" long and 6'10" wide and have an ordinary V-bottom with 18 degree deadrise at the stern. With engine, fuel and 2 persons onboard the weight is a little under 2000 lbs. Speed is measured with GPS and the rpm with the original Yamaha tachometer which I have checked with an external meter so it is accurate.

The engine is the classic Yamaha 90hp carburated two stroke. Recommended WOT range is 4500-5500 rpm. The gear ratio is 2:1. The engine is mounted so the anti-ventilation-plate is 2 and 1/8 inches above the keel. I am at the lowest boltholes so I can not raise it more. I have no jack-plate.

I have tested two props on the boat. First the Yamaha Pro Series 13,5 X 19 SS prop. It gave 40,5 mph top speed at 4600 rpm. The grip and the lift of the propeller was superior but I am a little low on the rpm so I doubt I reach full power, plus I think I am lugging the engine. I liked the characteristic of this propeller but I need lower pitch which is not available beacuse 19" is the smallest one Yamaha makes.

Second prop is a Powertech SCD3 13 X 17 SS prop. Powertech describes it as a sternlifting semicleaver performing like the standard Yamaha black steel propeller. With this propeller the boat reaches 42,5 mph at 5900 rpm. At full trim it easily ventilates but is otherwise performing good with a little less lift than the Pro series. I am also a little high on the rpm at WOT with this one.

My question is what propeller, brand, type and size should I try next to get the characteristics of the Pro Series but get my WOT rpm in the 5300-5600 range.

Best regards from Sweden!

Re: Tried 2 props, what do I try next?

A 13X19 would put it real close. Your main concern must be speed with the motor mounted so high. Normally it would be about 2" lower.

Re: Tried 2 props, what do I try next?

Thanks for your reply bhile!

I assume you mean a 13 X 19 Powertech SCD3 like the one I have but in 17 pitch. Yes, I think it would put me in the correct rpm range but it wont grip and lift the boat like the Pro Series does. What I am looking for is best possible overall performance. I think a propeller with similar characteristics as the Pro Series but in a lower pitch could give me just that. I just do not know which brand and type of prop that could be..

Re: Tried 2 props, what do I try next?

JARB.....The prop your swinging now sounds dead on to me, your getting a higher top speed and your WOT RPM is perfect, if you drop back down to 53-5600 your gonna lug it more than 5900. Your getting the full power out of that 2 stroke right now.

If you were losing top speed and concerned with that, I'd say increase pitch, but I would stay where you are. You also said you have "slightly" less lift, so if it's not all that noticeable, I'd leave it.

I am trying right now to get to 58 or 5900, if I could get 42.5mph at that I would be psyched.

Re: Tried 2 props, what do I try next?

Sounds like 18" would be perfect!!

I assume they don't make an 18" Pro Series.

Maybe someone here will know a company that does...

Bob

Re: Tried 2 props, what do I try next?

Thank you all for your replies!

I have found out that the Turbo1 and Stiletto is made in lower pitches and also have a slightly smaller diameter. Could any of these be something for me?

Re: Tried 2 props, what do I try next?

I just found out that the new Turbo Quest (SS) comes in a 18" x 13 1/4" size and is about $300. Sounds like just the ticket!!!

Of course the Stilletto in an 18" might be good also - if it comes in that size...

The Turbo 1 is a bow lifting prop for boats that need that to perform better.

IMO you want your top RPM's to be in the 5,400 - 5,500 range.


Bob

Re: Tried 2 props, what do I try next?

JARB said:

The engine is the classic Yamaha 90hp carburated two stroke.
I have tested two props on the boat. First the Yamaha Pro Series 13,5 X 19 SS prop. It gave 40,5 mph top speed at 4600 rpm.

Click to expand...

Strange stuff. 1st I find it very impressive that your yamaha 90 makes your 17' boat go 42.7 mph.

But what's more strange to me is that I have a Yamaha 115 on a 16' 1000lbs fiberglass boat that will only do 39mph (gps tested) alone in it @ 4600rpm. I have the same gear ratio as you. The propeller I have is the yamaha 13X21 pitch stainless. How can you boat go faster with less pitch at the same RPM ?

btw I ordered a turning point prop 13X19 and we'll see if I can get my RPM in the 5000 range. One thing I enjoy is having a quiet engine that will do 39mph. at 5000rpm then engine is a little more annoying LOL.

Re: Tried 2 props, what do I try next?

Ben Paquin said:

Strange stuff. 1st I find it very impressive that your yamaha 90 makes your 17' boat go 42.7 mph.

But what's more strange to me is that I have a Yamaha 115 on a 16' 1000lbs fiberglass boat that will only do 39mph (gps tested) alone in it @ 4600rpm. I have the same gear ratio as you. The propeller I have is the yamaha 13X21 pitch stainless. How can you boat go faster with less pitch at the same RPM ?

btw I ordered a turning point prop 13X19 and we'll see if I can get my RPM in the 5000 range. One thing I enjoy is having a quiet engine that will do 39mph. at 5000rpm then engine is a little more annoying LOL.

Click to expand...

My boat weighs 1200 lbs empty with no engine. At first I had a Yamaha aluminium prop on it in 13,25 X 17 and the anti-ventilation plate was even with the bottom. It then did 39 mph @ 5400 rpm. Switched to the Powertech SCD3 Stainless 13 X 17 and hit 41 mph @ 5600 rpm. After raising the engine I reached 42,5 mph @ 5900 rpm. I had lots of hope to the Pro Series but it was sadly too big.. Still looking for suggestions on alternatives..

The reason my boat is faster at the same rpm with less pitch is beacuse my prop was slipping less than your. The Pro Series prop have a very good grip in the water.

At 4600 rpm I do not think you are getting all the power your engine can produce. I think with your new 13 X19 prop you will see a higher top speed also. One thing that happened after I raised the engine was that I did get a little bit louder. Not much but noticeable. So if you want a quiet engine I do not think you should raise it.

Re: Tried 2 props, what do I try next?

Sounds like you allready know your stuff . Thought this might be a good read for ya .



http://www.marinedepo.com/proschool101.html

Re: Tried 2 props, what do I try next?

JARB said:

My boat weighs 1200 lbs empty with no engine. At first I had a Yamaha aluminium prop on it in 13,25 X 17 and the anti-ventilation plate was even with the bottom. It then did 39 mph @ 5400 rpm. Switched to the Powertech SCD3 Stainless 13 X 17 and hit 41 mph @ 5600 rpm. After raising the engine I reached 42,5 mph @ 5900 rpm. I had lots of hope to the Pro Series but it was sadly too big.. Still looking for suggestions on alternatives..

The reason my boat is faster at the same rpm with less pitch is beacuse my prop was slipping less than your. The Pro Series prop have a very good grip in the water.

At 4600 rpm I do not think you are getting all the power your engine can produce. I think with your new 13 X19 prop you will see a higher top speed also. One thing that happened after I raised the engine was that I did get a little bit louder. Not much but noticeable. So if you want a quiet engine I do not think you should raise it.

Click to expand...

Yeah I calculated my slip and it gives me 20% slip. That's a big boat slip number. I did have some water in the boat at times and I read a lot about the foam being stuck with water. I do find the stern to be a bit low in the water. Maybe my boat is heavier than the specs say it is.

Also I did raise the engine. The anti ventilation plate was lower than the bottom at first. Max speed was 39mph alone @ 4600rpm. Raised the engine two notch to make it almost even with the bottom. In fact it is just a hair over the bottom now. Top speed was 37.5 with 2 people on board. Seems pretty even. However I lost so much in my hole shot. The prop ventilates a whole lot on takeoff. So much if I floor it it sounds like it hit neutral. Also it won't turn hard like before. Strange that my boat can't handle the engine at this height.

When my GF drives the boat @ wot and I look at the engine. I can't even see the anti-ventilation plate in the water. It's still about 1" and a half in the water on a plane.

As for your boat and situation. It does not make sense than going from a 19" pitch yamaha stainless to another brand 17" pitch that it raised RPM by 800+.
From your original results I would recommend a 19 pitch stainless.

Re: Tried 2 props, what do I try next?

Hi Jarb,

you'll find that some of the experts here have a real preference for Turbo props. See the posts by Realmasa, for example. http://forums.iboats.com/search.php?searchid=600867

You should probably have a look at these:

http://www.turbo-props.com/files/Turbo-Page-3.jpg

On sale here for only $259:

http://www.boatownersworld.com/Props/turbo/turbo_1.htm

If you haven't already discovered this, here's a service that makes it real easy for us Scandinavians to shop in the US. Have used them many times to import propellers and electronics, at huge savings. See:

http://www.jetcarrier.com/


I've tried both the Stiletto and the Turbo, with the Turbo being slightly faster.

Good luck! Please post an update when you're done...

Re: Tried 2 props, what do I try next?

Hey stevens, good to see a post from you . . .

Re: Tried 2 props, what do I try next?

Thanks, QC. Have been away for a year - sold the boat last year as part of the divorce settlement. Now all settled in and just bought another boat ( http://www.batliv.com/photoalbum/view/?size=medium2&id=172471 ). Can't wait for summer to arrive again next year....

Re: Tried 2 props, what do I try next?

Wow, that thing is cool . . . Glad you made it out alive. Sorry for the hijack JARB.

Re: Tried 2 props, what do I try next?

Thank you all for your replies!

QC: Keep on hijacking, I am happy the more interest this thread gets!

stevens: Good to find some other Scandinavians here. Norwegian I guess? Very good tip about the jetcarrier service. I will look into it. Have ordered some parts myself from US but only from stores willing to ship to Sweden. With this service it seems you can shop from any store. Very nice boat you have bought. Made in Sweden it is

Ben Paquin: My PowerTech is a copy of the Yamaha Black Steel you have. Now at this height it ventilates quite easy during acceleration and in turns if I do not trim down the engine before turning/accelerating. Before the raise it never did. I do not think it is intended to operate at this height. My A/V-plate is al least one inch above the water at plane. A 19 pitch Black Steel style prop would probably get me in the correct rpm range but would most probably still ventilate easily. The Yamaha Pro Series is a completely different prop than the Black Steel/PT SCD3 with high rake, large diameter, progressive pitch and a alot of cupping. And a lot of grip, my slip is only 1% compared to 10% with the PT. I think that is why I lost so many rpms. I was told the Pro Series was hard to turn but could not imagine it was this hard. A Pro Series-style prop is what I think I need and it looks like the Turbo1 could be just that in 17" pitch. I was also told the PowerTech PTR could be worth trying. I think you too need a prop with more grip. I hope the Turning Point prop gives you that!

My next step will be to try and find a Turbo1, Stiletto or PowerTech PTR to try. It is soon time for winter lay-up here in Sweden but hopefully I will find a prop before that. of course I will post the results here.. Sooner or later..

Here is a picture of my boat. Not a very good one but I am away from home working and this is the only one I got here. Picture taken by the previous owner. It was the pic he used in the selling ad. Hope he do not mind..

Re: Tried 2 props, what do I try next?

I would start by investing in a jack plate my friend. I recently purchased a power lift manual with a 6" set back and 6" of lift for 229.00. It is the best investment I have made. If you want to truely see what rpm you can acheive with a particular prop, you must first get it at the optimal height for the least amount of resistance against the prop and put it into the "cleanest" water possible. This is only going to be reached with the addition of a jack plate.

Re: Tried 2 props, what do I try next?

Jarb here are my results with the turning point aluminum prop:

"
I just tested the turning point prop on my yamaha 115

What's nice is that I went from a stainless steel 21 pitch that did 39mph @ 4600rpm
to an Aluminum 19 pitch that does 40mph @ 4900 rpm. The prop cost me 70$

When I raised the engine the 21 pitch yamaha ventilated quite a bit.
I did not change engine height and now barely have any ventilation. Much better acceleration and handling. Also I can trim the engine so much more now and gain speed. Still 40mph is all I got trimmed out @ 4900rpm.

What's strange is the 19 pitch prop runs 36.5mph @ 4600rpm with the engine trimmed down. Similar to the yamaha 21 pitch. It just allows me to trim the engine quite a bit more without ventilating. "

Re: Tried 2 props, what do I try next?

Hi JARB,
I have a 19P Mercury Laser II for sale. Might be exactly what you need?

(Edit: Now sold to someone else, have removed the link above to the sales ad.)

Re: Tried 2 props, what do I try next?

(oops, double post):redface: