Best props for twin 50's ?

SeaCozy · Posted: Sat Jul 18, 2009 4:16 pm Post subject: Best props for twin 50's ?

I just purchased a 2002 22' Cruiser with twin Honda 50's with 100 hours and in "like new" condition. As I will use it mostly in Prince William Sound in Alaska, the twin outboards area a great safety backup feature should I lose an engine.
However, when I first took the boat out, on a local freshwater lake, with a single engine, I could only get about 4000 RPM and under 8 mph.. not up on step. From what I have read, the boat should be able to get up on step and at least 12-15 MPH with a single 50? With both, no problem, can get RPM right up high as I want at 30 MPH if desired.
The props are 11.1 x 14. I assume these are too "fast" for what I need. I am willing to sacrifice top end speed for better performance on a single engine (and in heavy seas, where I noticed boat bogging down at times).
Can anyone give me advice? Don't want to invest in two props and find they are "too little or too much." 13" or 12"?
We took it out in Prince William Sound for 5 days last week, and did great!
Thanks.

Matt Gurnsey · Posted: Sat Jul 18, 2009 4:31 pm Post subject:

With both engines what is the wide open RPM? What does the manufacturer say it needs to be?

You need to be sure that the engine is turning the recomended rpm at wide open to ensure proper load.

When doing your one engien tes, did you have the other engine tilted up out of the water to reduce drag?

SeaCozy · Posted: Sat Jul 18, 2009 5:33 pm Post subject:

I never maxed out RPM with both engines down, but easily over 5000 at 28 MPH, and am sure could have reached Honda max of 5500-6000 with max HP at 5750.
But with one engine (and yes, the other up and out of the way), I just would not exceed 4000 RPM, or get past 8 mph and up on step. I am pretty sure if I could get RPM up, thus increasing engine HP, it would get up on top.
Question... which props to buy? 13", 12", or even 11" ... without giving up too much top end?

Hunkydory · Posted: Sat Jul 18, 2009 6:30 pm Post subject:

SeaCozy

Do about the same as you on one Honda 40 with the other up. May be wrong but believe the difference between the Honda 40 and 50 is the ten hp at high rpm with the torque very near the same and its more torque than hp that puts you on plane. Unless you run extremely light which I doubt very much when running on the Sound, I don't believe you can come up with a prop that will do what you want.

Jay

hauptmaus · Posted: Sat Jul 18, 2009 6:45 pm Post subject:

I have a 2003 22 ft cruiser with a single 2003 Honda 50 used on the Chesapeake Bay. With two persons and a 65 pound dog it will run at 14 to 14.5 K at about 5200 rpm. The boat was purchased used at Cutters who before purchase, carefully pointed out the speed and passenger carrying limitations with 50 hp. However the price was right and my wife was not comfortable with the ride our previous boat, a 24 ft SeaRay which had a minimum planing speed of 22 K.

SGIDave · Posted: Sat Jul 18, 2009 7:38 pm Post subject:

Captains Cat · Posted: Sat Jul 18, 2009 8:31 pm Post subject:

I had stock props on my twin 45 CD22 and could not plane (maybe 8 knots or so) with one engine regardless of whether the other was up and out of the water or not. BTW, steering (with linked hydraulic steering) is very hard with one engine tilted up and the other down...

Charlie

jennykatz · Posted: Sat Jul 18, 2009 9:34 pm Post subject: props

I purchased a cruiser in 05 with a single 50 honda my recollection it had a 11in pitch i believe it woud rev to 55oo rpmand top out at 16 mph . try both engines first then try a 11or 12 in pitch on one eng if that works buy it for a spare for one engine
The real problem is putting the extra prop on in less then ideal conditions or just go down one pitch size when using both engines you would be at the top of the rpm range for your motor and then maybe you could get the boat to plane off if lighly loaded go see a good prop shop and ask

SeaCozy · Posted: Sun Jul 19, 2009 8:56 pm Post subject:

Thanks everyone. I am pretty sure the SD22 should be able to get up on step with a single 50 HP, based on what I have read, and comments above. The question remains... do the right props exist that will do OK with both engines, not maximum speed, but good all around, and in seas, and also be able to just get me up on step with a single engine.
I'll try to find a good prop shop for advice... so far their opinions have ranged wildly!
Too bad C-Dory isn't still around. I would assume they would have opinions on the subject based on experience.
Thanks again

Captains Cat · Posted: Sun Jul 19, 2009 10:48 pm Post subject:

Hunkydory · Posted: Sun Jul 19, 2009 11:34 pm Post subject:

Sure agree with you Charlie not only about C-Dory Factory verses C-Brats, but on one 50 getting the 22 on plane. There's lots of us CD 22 owners that would love to have that option now or in the past and have experimented getting there with the results being "maybe" if really light but its not going to happen with a CD 22 set up for extended cruise. Would love to be proven wrong, so SeaCozy if you can come up with what will work would love to hear about it.

Jay

Matt Gurnsey · Posted: Mon Jul 20, 2009 12:34 pm Post subject:

I sent this info to Sea Cozy via e-mail, but will add it here for general knowledge:

"If you attempted to prop the boat to run on one engine, you would be underpropped and not loading the engine enough. You would sacrifice cruise speed and risk engine damage.

The proper way to set the boat up is to determine what WOT (Wide Open Throttle) with both engines, and be sure you are in the manufacturer's recomended range. I would want to see your boat running about 6000 rpm with normal load on it for both engines.

At that point, whatever it will do on one engine is what it will do. Don't prop it for a condition that would be abnormal.

Also keep in mind that the four stroke engines don't have the torque of two strokes, so where it may run on plane with one of a pair of 50 horse two strokes, the four strokes won't provide that level of performance.

Hope this helps!"

As a comparison we repowered a 26 Striper with twin 175 E-Tec two strokes. The owner has a friend with the same boat powered by twin Yamaha 150 4 strokes. The Yamaha powered boat on one engine will acheive 13 knots, and not get on plane. The E-Tec boat will plane on one engine, and get to nearly 30 knots.

In fact, Evinrude has taken a boat and powered it with a a Yamaha 250 and an E-Tec 250, and do the single engine test. The Yamaha four stroke cannot get the boat on plane, the E-Tec can.

I think the 4 strokes just don't have the torque to plane the boat with one engine. Look at it this way- if a 50 horse would plane the boat, why run a 90 on single applications?

My concern is that propping to run on one engine, will mean that the engines will be able to over rev, and will not acheive economical cruising speeds when running together.

Fishhawk · Posted: Mon Jul 20, 2009 1:07 pm Post subject:

SeaCozy,