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Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Nissan 9.8 outboard 4-bladed prop

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jaclasch
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USA
104 Posts

Initially Posted - 05/03/2006 : 18:12:41

I heard Nissan was releasing a 4-bladed prop for the Nissan 9.8. I sent an email to Online Outboards this morning inquiring about this and received the following:

Hi James,

Thank you for your email. Yes, the 4-blade props are coming available in about 30-45 days (estimate from Tohatsu/Nissan). None have actually come in yet, as they are still in production. 2 sizes are available, a 4-blade 10" dia. X 5" pitch, and a 4-blade 10" dia. X 7" pitch. Both are the same price. It fits the 8hp and 9.8hp Tohatsu/Nissan - all models.

I strongly recommend backordering. The factory already has a long list of backorders for both.

Cost: $69.99 + $10.00 shipping = $79.99 total price.

If you wish to order, please give me a call at 888-681-9073 or use the form below:

www.onlineoutboards.com/ebay_payment.html

Enter Quote# CC3899 in the comment section of the order form to receive the price quoted here and also if you would like the 5" pitch or 7" pitch.

Thanks,
Chris Collins
National Sales Manager
http://www.onlineoutboards.com
sales@onlineoutboards.com
Toll-Free 888-681-9073

P.S. Also, feel free to post this message at the boards if you use them on the association's forum. I know a lot of people would be interested to learn what is available and a time line on availability. You can include the entire message with order form and quote # if others wish to backorder they can use the same quote #.
(end of Chris Collins email)

Now then. What pitch should I be using for my Catalina 25?

James
1983 FK/TR
Tiempo Dorado

Edited by - on

Tom Potter
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1913 Posts

Response Posted - 05/03/2006 : 18:50:27

Good info, Thanks James.

Edited by - on

Gloss
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USA
1916 Posts

Response Posted - 05/03/2006 : 19:12:57

I have an 8 hp Honda power thrust model. It has a 4 blade 10" x 6 1/2" pitch. I don't know if that helps you or not. Plenty of power, I can hit hull speed easily, but it also has enough torque to get me through a 6 foot chop with 15 knot headwinds. The 8 hp honda has a cam to deliver more low end torque than the 10 hp model.
How this helps you with a Nissan/Tohatsu/Mercury motor, I haven't the foggiest. It just seems that a 5" pitch maybe a bit too low, maybe it's for a houseboat.

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 05/03/2006 : 19:45:59

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Gloss
 It just seems that a 5" pitch maybe a bit too low, maybe it's for a houseboat.
<hr height="1" noshade id="quote"></blockquote id="quote">
Frank's absolutely right. The prop he describes (I have the same engine and prop) is arguably a little too low pitch for the C-25, for pure fuel economy purposes, and more than adequate for purposes of maneuvering around a dock, where thrust (particularly in reverse) becomes the issue. If you feel you'd like a little better stopping power and backing power, go for the 7" version. If your main concern is miles per tank cruising, and you have no issues with maneuverability, you might want to stay with the stock prop.

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Gloss
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1916 Posts

Response Posted - 05/03/2006 : 20:03:51

Another thing which Dave and I didn't ask, is where you will be sailing. If you are going offshore and may get into bigger seas, you would want a prop with lots of bite. IMHO that would be the larger diamater prop. Do you agree dave?

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 05/03/2006 : 21:25:54

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Gloss
 Another thing which Dave and I didn't ask, is where you will be sailing. If you are going offshore and may get into bigger seas, you would want a prop with lots of bite. IMHO that would be the larger diamater prop. Do you agree dave?
<hr height="1" noshade id="quote"></blockquote id="quote">
Not necessarily. The larger diameter is mostly an offset for the lower pitch, allowing the engine to run at higher RPMs in low-speed situations, due to the pitch, but moving more water, due to the length of the blades. That's key when accelerating from a stop or trying to get to a stop. Under way, the greater pitch lets the engine run at more efficient RPMs, and gives you a little reserve if you need more push, but a smaller blade is appropriate to offset the greater pitch.

Arlyn Stewart has reported (I hope I get this right) that he misses the higher pitch, smaller diameter prop of his Honda "classic" 8 when cruising on Lake Huron (not exactly small water)--albeit in a somewhat lighter C-250--because he has to run his newer "Power Thrust" Honda at higher RPMs (getting lower gas mileage). It could be that if he needed some reserve power to maintain cruising speed, he'd have less with the larger, flatter prop. Fortunately, the Honda 8 has plenty of power left regardless of the prop... But essentially, I would not suggest that the "high thrust" configuation is best for everyone. I will only suggest that it's best for low-speed maneuvering, which was important to me when I bought my newer Honda.

Edited by - Dave Bristle on 05/03/2006 21:30:11

jaclasch
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104 Posts

Response Posted - 05/03/2006 : 22:19:46

I am confused by the talk about "diameter." The props being discussed are both 10-inch diameter props. One is 5-inch pitch and the other is 7-inch pitch. I must have missed something along the line.

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dlucier
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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 05/03/2006 : 22:29:36

James,

Do you find your current prop lacking?

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jaclasch
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104 Posts

Response Posted - 05/03/2006 : 23:03:24

I do not like it for backing up and getting around and out of the marina as well as my old Honda 8. It had more of a feel of biting into the water at low revs.

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atgep
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1009 Posts

Response Posted - 05/03/2006 : 23:17:54

WHen comparing the Honda to Nissan dont forget the gear ratio in the lower unit.

The Nissan has a 2.08 to 1

Honda has a 2.43 to 1 ratio.

This means a flatter pitch may be more appropriate on the Nissan 9.8 than the Honda or other "high torque" motors. Even with the smallest pitch prop currently avaiable, I only hit 4950 rpm at full throttle. When the 4 blade comes to market, I will try to get one for testing. As for the guts of the 8 and 9.8 the only differance is carb diameter and jetting.

Tom.

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lcharlot
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Antigua and Barbuda
1301 Posts

Response Posted - 05/04/2006 : 07:08:10

My Yamaha T8 came with a 5" pitch prop, and from almost the first time it was in the water, I didn't like it. To get the boat moving at hull speed, the engine would have to be revved at nearly max RPM's. As soon as I could scrape the cash together, I bought a 9" pitch prop, which is the standard prop for the Yamaha T9.9 and has the same hub spline as the T8.
Pros of using the 9" pitch: better fuel economy, quieter operation of the engine.
Cons of using the 9" pitch: slower acceleration from a dead stop, engine can not achieve max RPM so can not get max horsepower. Some reduction in output from charging coil.
Overall I am much happier with the 9" pitch. Since my home water is a lake, I don't have to contend with tides or currents so don't need maximum horsepower. The 9" prop moves the boat at 5 knots at about 1/3 throttle, or 4 knots at 1/4 throttle, and that's as fast as I ever need to go.

Edited by - on

Dave Bristle
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Djibouti
10005 Posts

Response Posted - 05/04/2006 : 08:11:01

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by jaclasch
 I am confused by the talk about "diameter." The props being discussed are both 10-inch diameter props. One is 5-inch pitch and the other is 7-inch pitch. I must have missed something along the line.
<hr height="1" noshade id="quote"></blockquote id="quote">
Sorry--I was assuming your OEM prop had a smaller diameter as well as a higher pitch--Yamaha offsets the lower pitch with a larger diameter, while Honda does it mostly with the extra blade. (Honda also improved backing thrust by diverting the exhaust away from the prop in reverse, which gives better bite.)

What is the pitch of your current prop? If you're not satisfied with the backing or starting power, go lower--if your current is 9, I'd go to 7. If it's 7, then try 5, (a pretty big difference), but I wouldn't go from 9 to 5. (I used to do that--never again!

)

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RSHOOTER
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Response Posted - 05/04/2006 : 08:11:40

Well, after reading all this I am thoroughly confused! I have a C250 Wing Keel and want power at low speeds for Lake sailing. Which pitch for the 10" Prop is right for me?

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atgep
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Response Posted - 05/04/2006 : 08:41:39

I would advise you to use the stock prop as there is no other choice when buying a new Nissan/Tohatsu. If find the performance unacceptable, then look to change it.

With the stock prop, the engine did not have very good feel. The engine appeared to achive maximum power at half throttle. I put a tach on it and it was peaking at half throttle. Max rpm was 4400. The recommended factory rpm is 5000-6000. I dropped to the lower pitch and rpm came up to 4900 at full throttle. The engine reponse seemed better.

I Took a long motor trip and my milelage average with the 2 other boats with simmilar engines.

If you look at the prop on the nissan, it is nothing like the Honda or Yamaha, It looks like a high speed design.

I hope this helps.

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RSHOOTER
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Response Posted - 05/04/2006 : 08:55:56

If you read the first post it announces two four bladed props with different pitches for the Nissan/Tohatsu 9.8 I have the Outboard with stock prop and am considering changing the Prop to one of these...which would give me better thrust at low speeds?

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jaclasch
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104 Posts

Response Posted - 05/04/2006 : 09:25:18

I asked Chris Collins of Online Outboards what the benefits would be If I changed to the new 4-bladed prop. Here is his reply:

Hi James,

I'd say based on my past experience with other motors my recommendation
would be the 7" pitch. I believe the 4 blades alone and larger diameter
will make a pretty drastic difference. The 5" could cause the engine to
turn more rpms than necessary and you may not see much performance
difference but would burn more fuel. I'll have to check out your link. I'd
love to hear feedback once you guys get them on the motors and use them a
bit.

Thanks!

Chris Collins
National Sales Manager
http://www.onlineoutboards.com
sales@onlineoutboards.com
888-681-9073 Toll-Free

Edited by - on

jaclasch
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104 Posts

Response Posted - 05/04/2006 : 17:31:47

The following correction is from Chris Collins at Online Outboards:

"Tohatsu America informed me that the diameter of the new 4-blade propellers is NOT 10 inches as they originally thought but is instead 8.7 inches. The two pitches available are 5-inch and 7-inch."

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atgep
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1009 Posts

Response Posted - 05/04/2006 : 18:58:10

It will be interesting to see what the prop will do. I never got around to testing the thrust differance between the 7.5 and 6.5. The engine does seem more responsive with the 6.5.

I think if there is enough blade area on the 5 in 4 blade prop, It may improve the thrust in bad conditions.

Prop efficiency has everything to do with the "slip" the prop creates. The lower the slip, the better the response is and the less it is like a jetski.

Tom.

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dlucier
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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 05/04/2006 : 19:53:34

This topic is eerily similar to the one I posted a year or two ago when I experimented with a new Mickey Mouse eared, 9.75" X 6.5" prop on my outboard that was running a conventional 9" X 9". With the new larger diameter/lower pitch prop, my top speed was reduced by about a knot, and I had to use much higher rpm's to get there which resulted in very poor fuel economy over the old prop setup.

Aside from the lower top speed, open water performance between the two props was pretty much immeasurable. Inside the marina, where I expected the greatest performance difference, I found that since I use the outboard so sparingly, the better bite of the new prop didn't do me any good.

So for the sake of better fuel economy and a higher top speed, I admitted defeat and put the original prop back on.

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atgep
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Response Posted - 05/04/2006 : 22:25:49

Don, Which motor are you refering to?

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dlucier
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Response Posted - 05/04/2006 : 22:41:56

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by atgep
 Don, Which motor are you refering to?

<hr height="1" noshade id="quote"></blockquote id="quote">

Mercury 8hp 2 stroke

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tinob
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USA
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Response Posted - 05/08/2006 : 12:12:48

Guys,

Chris Collins might be amenable to letting one of us (willing) to test two of the new four blade props in an attempt to settle the discussion. I would volunteer, but changing props in water is one of my least favorite activities. A person trailering their boat might be the one to go for. Of course we are talking about three different hulls, each with dissimilar requirments. But a c25 might be used initially, and it might serve as a stepping off point for all when the effect on one hull type is viewed.

What do you think?

Val on Calissta # 3936 Patchogue,N.Y.

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atgep
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Response Posted - 05/08/2006 : 19:23:43

I will volunteer for this tough task. I have been a thorn in their side about this issue of wanting a prop with more square inches of bite. I have a tachometer and will be available for testing in July. It would be good to test all the props.

Tom.

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tinob
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Response Posted - 05/09/2006 : 08:44:02

Tom...I had you in mind when I suggested we make the offer to Chris.

Val on Calista # 3936 Patchogue, N.Y.

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