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Tohatsu Propeller Guide

Tohatsu Propeller Guide

Tohatsu Propellers

The standard propeller supplied with the outboard is indicated in the brackets i.e. (S,L) would be supplied with a short and long shaft model. Other propellers can be purchased to achieve different performance. Please refer below to our Choosing a Propeller guide.

The goal in propeller selection is to determine what style and size will maximize your boat's performance, while allowing your engine to operate in the recommended r.p.m. range. The correct propeller will prevent the engine from over-revving, yet allow it to reach the minimum r.p.m. at maximum horsepower. 

If the engine over-revs beyond the maximum recommended r.p.m., you may need to increase the pitch of the propeller. Increasing the pitch increment by 1" will result in approximately a 150-200 r.p.m. reduction at wide open throttle (WOT). If you cannot reach maximum r.p.m. at WOT, then pitch should be decreased. These recommendations apply to single engine installations only. For most twin engine installations it is necessary to increase pitch by 4". Adding diameter will typically decrease rpm, while reducing diameter will raise the rpm.

Propeller selection will depend on your usage. Ski boats need more top end speed, and should choose a prop with a higher pitch. Cruisers and houseboats need more performance at displacement speeds, and should use a prop with a lower pitch to achieve low-end power. It is essential, however, that the WOT r.p.m. falls within the range specified by your engine. If your engine is not able to reach this r.p.m. range, it's operating under an extremely loaded condition. 

If the propeller supplied with your engine is not providing desired performance follow these rules to help choose a different prop:

1. Consult owners manual to find recommended wide open throttle RPM range for your engine.

2. Determine current WOT RPM and speed using existing propeller. Vary trim to achieve maximum speed. 

3. If existing propeller doesn't achieve RPM within specified range at WOT select larger or smaller pitch to achieve this. 

-Adding 1 inch of propeller pitch will reduce WOT RPM by 150 to 200 RPM.

-Subtracting 1 inch of propeller pitch will increase WOT RPM by 150 to 200 RPM

4. A 4 blade propeller will usually generate 50-100 RPM less than an equivalent pitch 3 blade propeller. 

Aluminium Propeller Verses Stainless Steel Propeller

Most outboard engines come with Aluminium propellers as standard as they are inexpensive and suitable for all round use. Stainless steel propellers are much stronger, more expensive but also offer greater performance. Upgrading to a stainless steel propeller however is a relatively cost effective way of achieving increased performance including improved acceleration and top end speed.

Blade Propeller Verses 4 Blade Propeller 

If the propeller is likely to remain submerged at all times, a three-bladed prop usually provides better top speed performance. Most standard propellers are three-blades. A four-bladed propeller can provide better acceleration and is more widely used in craft that pierce the surface or the propeller is very shallow.

The propeller selection chart can be used to help you in selecting the correct propeller for your Tohatsu outboard. Remember that in any application, discrepancies in performance can result due to the different boat hull designs, the final carrying load and your particular needs.


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