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ISO Tohatsu/Nissan Propeller

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BCG-Woodbury
Mainsheet Editor

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USA
396 Posts

Initially Posted - 07/09/2014 : 17:59:49

I'm looking for a source of a new or slightly used propeller for my 2006 8HP 4-Stroke Outboard. The motor comes with an 8.5"D x 7.5"P however the manual suggests an 8.5"D x 6.5"P for heavy boats. So far I've been able to locate the correct size but they had no stock. If anyone has a good source for outboard propellers, please point me in the right direction. The current prop does the job but I get no change in speed between 1/2 and Full throttle. The speed is also pretty slow, maybe 3-4 knots.

Thanks,

Edited by - on

Stinkpotter
Master Marine Consultant

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Djibouti
9017 Posts

Response Posted - 07/09/2014 : 21:50:05

Hmmmm... How's your bottom? Your 8 should do better with almost any prop.

Edited by - on

dasreboot
Admiral

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803 Posts

Response Posted - 07/10/2014 : 03:58:15

on my 9.9 honda i get only 1/2 knot more between half and full throttle, but it uses a lot more fuel. 5 at half throttle 5.5 at full.

Edited by - dasreboot on 07/10/2014 03:59:42

TakeFive
Master Marine Consultant

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2269 Posts

Response Posted - 07/10/2014 : 08:45:06

quote:
Originally posted by BCG-Woodbury

I'm looking for a source of a new or slightly used propeller for my 2006 8HP 4-Stroke Outboard. The motor comes with an 8.5"D x 7.5"P however the manual suggests an 8.5"D x 6.5"P for heavy boats. So far I've been able to locate the correct size but they had no stock. If anyone has a good source for outboard propellers, please point me in the right direction. The current prop does the job but I get no change in speed between 1/2 and Full throttle. The speed is also pretty slow, maybe 3-4 knots.

Thanks,

A lower pitch prop will not get you more top speed. It will probably get you less, and/or higher RPMs at top speed, which might actually damage the motor.

Lower pitch may get you quicker starts if you gun it, which might be helpful maneuvering in tight confines of a marina.

Same principle applies for power boats, where lower pitch gets you better "hole shot," useful for pulling waterskiers. But it comes at the expense of top speed, and at the risk of revving RPMs dangerously high.

Ultimately, your pitch should be selected to get the manufacturer's specified RPMs at full throttle, so that the motor can deliver its full power. Heavy boats may need the lower pitch if they cannot get to full RPMs. But what you describe does not sound like that.

Edited by - TakeFive on 07/10/2014 09:39:32

BCG-Woodbury
Mainsheet Editor

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USA
396 Posts

Response Posted - 07/10/2014 : 09:52:07

The bottom is good, we are on a lake and the Interlux ACT completely eliminates the slime. I was just going by what the manual said for heavy boats. Most of these 8 HP Outboards are clamped to a rowboat, not a dead whale. For about $50 it will be worth the trial. I'll let you know the results.

Thanks,

Edited by - on

Heartbeat
Navigator

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USA
161 Posts

Response Posted - 07/17/2014 : 14:18:06

My Tohatsu 8 pushes me at 6.3 at ~4300 RPM. Since the motor was designed for a higher RPM, I considered a lower pitch prop, but never did it. (I didn't want the fuel usage to go up.)

Did you try buying a prop from here?
http://www.tohatsuoutboardparts.com/

Matt

Edited by - on

BCG-Woodbury
Mainsheet Editor

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USA
396 Posts

Response Posted - 08/11/2014 : 19:17:30

I picked up a new prop the other day. It is a 4-blade with a slightly larger diameter and a better pitch that is considered a "high-thrust" version. Put the prop on last week and it pushes Knot So Fast at a much better pace. If anyone is interested in the specifics, let me know.

Edited by - on

panhead1948
Captain

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345 Posts

Response Posted - 03/03/2015 : 12:34:00

I'm thinking of a tohatsu 8hp and am looking for a high thrust prop. let me know the details. KJ

Stinkpotter
Master Marine Consultant

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Djibouti
9017 Posts

Response Posted - 03/04/2015 : 10:15:08

The pitch of a prop is designed, in part, to match up to the operating speed of the boat. Too much pitch with a displacement hull (e.g. C25) makes the prop behave somewhat like a paddle-wheel, thrusting water outward and increasing "prop-walk." "Standard" props are meant to carve through the water at planing speeds, as on an inflatable. A lower pitch, "high-thrust" prop thrusts aft more efficiently at low speeds through the water, so makes more efficient use of the motor's power, and doesn't necessarily use more fuel even if the RPMs are a little higher. Braking and backing are also greatly improved. When I went from a 1990s vintage Honda 8 to a 2003 high-thrust Honda 8, the difference was striking--especially the stopping power. MPG at cruise might have been a little lower, but not so that I noticed the difference for a season. (Mine is a LOT lower now!

)

What really eats gas is trying to get above about 5.5 kts in a C-25.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 03/04/2015 10:19:18

MarkV
Deckhand

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6 Posts

Response Posted - 03/04/2015 : 10:53:39

Brian,

You might try Precision Propeller repair; 78 Bridge St.; Newburgh, NY. (845) 562-3880

Mark

Tomas Kruska
Admiral

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Czech Republic
522 Posts

Response Posted - 03/04/2015 : 12:18:13

quote:
Originally posted by BCG-Woodbury

I picked up a new prop the other day. It is a 4-blade with a slightly larger diameter and a better pitch that is considered a "high-thrust" version. Put the prop on last week and it pushes Knot So Fast at a much better pace. If anyone is interested in the specifics, let me know.

Please share the part number for that prop. Is it 4-blade 8.7 x 5 RH?
Do you get the same hull speed with higher revs or same?

Dalpol Phobos 21, 2013, Sole Mio, hull #27, current adventures - We sail Phobos 21

PO of Catalina C25, 1978, High Anxiety, hull #701, SR, FK, L-dinette, inboard diesel Volvo Penta MD2010C w/saildrive - more info

Edited by - Tomas Kruska on 03/04/2015 12:19:00

BCG-Woodbury
Mainsheet Editor

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USA
396 Posts

Response Posted - 03/04/2015 : 20:08:21

I ended up with more throttle range. The old prop's speed would max out at about 1/2 throttle. Maybe 3-4 knots. The new prop gives a linear speed up to full throttle and maybe 5+ knots. I'll dig out the box this weekend and report the size.

Brian & JoAnne Gleissner
Knot So Fast
1984 Catalina 25, SR/SK
Traditional Interior
Lake Candlewood, CT

Voyager
Master Marine Consultant

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USA
5239 Posts

Response Posted - 03/08/2015 : 19:24:30

Brian,
On Passage with the Honda 8 with a 4-blade prop, I can do 4.5 kts no sweat - the engine just purrs along, and if I push it hard, I can get her up to 5.5 kts. It'll scream and drink a lot of gas but when we've got someone aboard who's seasick or gotta go in a hurry, the extra oomph makes all the diff. Good luck with the new prop.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

BCG-Woodbury
Mainsheet Editor

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USA
396 Posts

Response Posted - 03/15/2015 : 16:48:07

I ended up getting a Tohatsu High-Trust 4-Blade prop, here are the specs.

AMITA 3
IN: INW14030037
T8 4X8.7x5RB
P/N: 3B2B645110
Material: Aluminum
Rotation: R
Blade: 4
Diameter: 8.7
Pitch: 5

Fits Tohatsu/Nissan 8, 9.8 (Both 2&4 Stroke)

Brian & JoAnne Gleissner
Knot So Fast
1984 Catalina 25, SR/SK
Traditional Interior
Lake Candlewood, CT

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.