Alum SDS and GP SDS Prop on F70LA

[lrg-35553]

I have a F70LA on a 17.5 ft Alum boat. Current prop is a 6E5-45947-00-00 which is a 13 1/2 x 15. Performance is fine but I do not like the clunk when going into gear and the shake at lowest RPM. I am looking at the Talon SDS to solve the concerns but notice some dealers commenting that for the same performance the pitch should be lowered, up to as much as 3 inches. There is alum SDS #6EK-45947-00-00 which is a 13 1/2 x 14. There is also a alum GP SDS #6FP-45943-00-00 which is a 13 1/2 x 15. Can you clarify the comments on lowering the pitch because of a more aggressive blade design and what about the GP.

Len

[boscoe99]

First thing we need to know is what is the WOT RPM with the boat loaded and the motor trimmed up just to the point of maximum efficiency?

[lrg-35553]

About 6200 which I considered good

[99yam40]

What is the idle RPM when it goes clunk?

Is this a heavy SS prop?

some of the plastic owner replacement /repairable hubs do make some noise if SS props are used from what I have read.
never heard of over 6K being in spec, but what do I know

[pstephens46]

I would hope whoever sells this prop would give you the chance to test and return. Be lucky to hit it just right on the first try. I have heard the SDS props run "heavy". Meaning a little less pitch than whatever you had prior. If you are hitting 6200 rpm you may want just a small reduction in WOT rpm. Maybe not...
Up to you.

Not sure about aluminum.

[boscoe99]

RPM red line on the F70 is 6300.

Strange that clunking is an issue when using an aluminium propeller but...

[boscoe99]

About 6200 which I considered good

Perfect on the WOT RPM.

As pstephens notes, it is best if you can find and try some different propellers before you buy one. Easier said than done however.

To make life a bit more difficult there are three versions of Talon propellers. Talon in aluminum, Talon GP in aluminum and Talon SS in stainless steel. All three use the SDS hub. I have no data to indicate how each compares to the other from an agressiveness standpoint or how they compare to your current propeller which uses a pressed in hub.

If it were me I think I would start with the Talon GP with a 13 1/2" diameter and 15" pitch. Same as what you have now. With the hope that the blade geometry is all but identical to the propeller that you have now. See if the dealer will let you return the new propeller if it drags your WOT RPM down too much. Or, if you can really trust the dealer who is suggesting a Talon GP with a 14" pitch I would not be adverse to starting there.

I much prefer to see a motor slightly under propped than over propped at all.

Good luck.

[pstephens46]

I'm impressed a dealer rigged the motor to get 6200 rpm.

Seems many new boats/motors are rigged now to poot along at 5500 rpm trimmed with two people on board.

[lrg-35553]

Actually, I picked that prop after reviewing the Yamaha performance data sheets. The problem is that on the eastern shore of Lake Ontario it is usually very windy and difficult to dock. The one criticism I have about the Yamaha F70 is that when you pull back to Idle speed it takes about 3 seconds to actually get back to idle RPM. It is easy to say to "anticipate" what is going to happen but with a 25 Knot wind from any direction it is difficult at times to dock. I have two F70's, one on a pontoon and one on a 17.5 alum fishing boat and they both act the same. At times it is necessary to change gears without waiting which could be above 1000 rpm, thus the clunk! I have over 50 years of boating experience with inboards, I/O's and many 2 stroke outboards. Never had that type of issue on any of them. I have less trouble pulling into a slip with a single inboard on a 28 ft boat which is sort of a con*****ed collision. I have had others tell me they see a similar issue with lingering high idle on the Evinrude E-Tec also. The last problem is I also feel that there is a bit of shake when *****ing at 700-800 rpm. Hoping to reduce both problems with an SDS.

[pstephens46]

Actually, I picked that prop after reviewing the Yamaha performance data sheets. The problem is that on the eastern shore of Lake Ontario it is usually very windy and difficult to dock. The one criticism I have about the Yamaha F70 is that when you pull back to Idle speed it takes about 3 seconds to actually get back to idle RPM. It is easy to say to "anticipate" what is going to happen but with a 25 Knot wind from any direction it is difficult at times to dock. I have two F70's, one on a pontoon and one on a 17.5 alum fishing boat and they both act the same. At times it is necessary to change gears without waiting which could be above 1000 rpm, thus the clunk! I have over 50 years of boating experience with inboards, I/O's and many 2 stroke outboards. Never had that type of issue on any of them. I have less trouble pulling into a slip with a single inboard on a 28 ft boat which is sort of a con*****ed collision. I have had others tell me they see a similar issue with lingering high idle on the Evinrude E-Tec also. The last problem is I also feel that there is a bit of shake when *****ing at 700-800 rpm. Hoping to reduce both problems with an SDS.

Is it necessary to approach the dock with any other setting other than idle speed? Con*****ing speed by bumping from neutral to idle seems to me a more con*****ed approach. We have wind and tidal current here. 6-9 feet depending on day of month.

[TownsendsFJR1300]

What's the idle RPM in gear and in neutral?

That engine does have a single throttle body:
http://www.boats.net/parts/search/Ya...201/parts.html

[lrg-35553]

Boat is currently in storage, will be pulling it out this weekend. As I recall idle in gear and idle in neutral RPM are in reasonable range. (After waiting 3 seconds for lingering high rpm to dissipate).

[TownsendsFJR1300]

Boat is currently in storage, will be pulling it out this weekend. As I recall idle in gear and idle in neutral RPM are in reasonable range. (After waiting 3 seconds for lingering high rpm to dissipate).

Bolded ^^, maybe not a big issue but it shouldn't do this...

With the throttle pulled back fully, it shouldn't be "idleing" for over 1,000 RPMs, even for 3 seconds.

This may be pointing towards a "something wrong issue", whether it be synced properly, fuel issue, etc...


Has anyone ever plugged in a YDS and checked for codes, etc on this engine?


.

[pstephens46]

Wonder if the linkages are moving at the same rate of throttle down?
Is something dragging or binding?

[TownsendsFJR1300]

Wonder if the linkages are moving at the same rate of throttle down?
Is something dragging or binding?

Maybe some binding, but I kinda doubt it. IF after 3 seconds (along time actually when docking AND shifting) idle drops down, the linkage is probably ok. Easy enough to look at and check.

But shifting (docking in a hurry) with those RPM's will result in damage to the LU...