Did the Dealer install the wrong prop?

[mswalter2009]

First off, thanks everyone for all of your expert knowledge you post to this site!!!

I just repowered my 18 cc with a 2008 Yamaha 90hp two stroke. Broke in the engine this weekend. The prop that was installed was a SS Michigan Wheel Apollo Series 13 1 / 4 by 17. This prop would hit the standard trim anode so the dealer either installed a different or ground down the stock tab to about 1 / 4 inch profile. Dealer says this a Yamaha part number called a ?Sport Tab?. Anyone seen this before? Don?t want to slam the dealer but I can?t find any such Yamaha Part.

The depth of this prop is such that the blades cross the anode tab mount about three quarters or more through the circular diameter of the mount. And, the tip of the blades are pretty close to the anode. A little more than a quarter inch. I just don?t see how any tab could be used. Is this prop just not designed for use with this engine?

From my knowledge (and this site) I should have a tab that counter acts the rotation of the prop in case the steering were to break. Is this correct?

Engine mounting ? With the engine trimmed full down the cav plate is below the hull about 1 / 2 inch or more. Shouldn?t this be 1 / 2 inch above?
Max rpm is 4500 and you can tell the boat is dragging. Lots of throttle left at 4000 to WOT but only not a lot of mph gain from 4000 to WOT. Bow seems to dig at WOT and you can?t adjust the trim to lift the bow very much before cavitation.

Performance ? The 13 ? by 17 prop seems to be the right size and pitch. Jumps on a plant, cruises nice at about 3800 to 4000. But after 4000 just seems to drag.

Boat ? 18 Privateer CC. (bay boat) Dry weight 1250. Very slight deadrise in the stern.

 

[gcboat]

Re: Did the Dealer install the wrong prop?

1) Shouldn't need to grind or deface the trim anode AT ALL !!!!! Sport Tab ???

2) Sounds like they have installed the wrong prop

3) A tab, yes. But it will not help you that much if your steering takes a dump.

4) I don't think that 1/2" difference will affect your performance.

5) I'd take it back to the dealer and definately explain your feelings to them. Be armed with all the info and thoughts you expressed here.
Please keep us up to speed on the results.

 

[mswalter2009]

Re: Did the Dealer install the wrong prop?

I did find the tab the dealer was talking about but the one on my engine looks like it was ground down. Good clean job but ground down.
http://www.boatzincs.com/yamaha_outboard.html



Checked the Michigan Wheel site and it states that the above mentioned part number "may" be required when using this prop. I'm not even sure I could use the Yamaha high clearance tabs like pictured below.

 

[Barnacle_Bill]

Re: Did the Dealer install the wrong prop?

That prop is too big. Be sure to tell the dealer what your RPMs are at WOT.

 

[mswalter2009]

Re: Did the Dealer install the wrong prop?

Bhile - You mean diameter right? It is a 13 1/4. Would a 13 be a better match. Whats the performance difference in a 13 1/4 compared to a 13.

I think with a 13 I can get a "high clearance tab" to work. Pictures coming.

My WOT rpm was 4500 (low side as it would bump into 4400) I was expecting more.

 

[mswalter2009]

Re: Did the Dealer install the wrong prop?

picture of the prop and clearance.

 

[gostephen]

Re: Did the Dealer install the wrong prop?

you have plenty of clearence in that pic
i would just get the new anode

 

[Dhadley]

Re: Did the Dealer install the wrong prop?

Check the AV plate when the motor is trimmed so the plate is parallel to the keel. It should be no lower than even. With a high rake prop like that one it will probably work quite a bit higher. If you can use 100% of the trim and not vent the prop it can probably go higher. Once you get the height (X dimension) worked out the top rpms will, most likely, be higher.

 

[mswalter2009]

Re: Did the Dealer install the wrong prop?

Thanks for the tip. I will double check that. After my first day of break-in I had the boat in the drive-way with the engine trimmed all the way down. Eyed it and it was below the hull but the AV plate might not have been parallell with the hull.

Excuse the possibly dumb question but what do you mean by a high rake prop? I just wanted a "regular" SS prop for my engine. Michigan Wheel was recommended by the dealer for the value. Again thanks.

Answered by Google: Rake of the blades is the next consideration, a low rake prop has the most power and a high rake has the most speed and lift. Rake is the angle of the blade in relation to the hub, 0 rake being 90 degrees. The better running props are usually in the 20 through 30 degree rake angles.