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merc / yamaha prop charts


Fishing Junky

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I am confused!

I have a 16.6 ft lund with a 90 hp yamaha four stroke .

The dealer set it up with a 17 pitch prop and full of gas and two fishermen it runs 35 mph 5000 rpm .

Yamaha owners manual says the RPM's should be 5500 to 6000 when wide open .
And their prop charts and Mercurys prop selector put me in a 23 to 24 pitch prop .


If I increase the prop pitch from my 17 to what they recommend wont my rpms be even lower ?

Should I strive to match the recommended RPMs and lower my pitch or what ? ? ?


help !

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I have a 1999 F100 Yamaha (4-stroke) on a 1999 Lund 1700 Angler SS. Mine mounted 1 hole up gives 6000 rpms at WOT. I had my dealer make sure the boat tach was functioning properly. They checked it against the one in their shop and it was 200-300 rpms low. I wanted to do this before I started playing with props and motor height. That prop should be close to the right pitch for your rig.

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I have a 2002 Yammi on my Lund...

I am not impressed with the prop at all. Me alone in the boat it does fine, but fill it with gas, one guy, and a livewell full of fish and she struggles to move.

Same HP and size boat as my other rig...and I used to be bale to put 2 guys plus myself and gear and a livewell of dandys and hardly tella difference...

Time for a different prop I think...

good fishing and have a safe and fun holiday weekend

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You need to check your tach. They are switchable to be used with 2,3,4,and 6 cyl. engines so your tach may very well be set wrong. With your setup you should probably be able to turn something in the 18 to 21 pitch range and get proper rpm,s with a little trim. Each 2' of pitch will raise or lower your rpm about 400 opposite of the way you go numerically ie higher pitch lower rpm and vice versa. But have your tach checked because it appears that it may be set wrong. grin.gif

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Thanks for the ideas it may well be the tach is off though it does not sound like the motor is reving to high . I will have the tach tested .

The model is a Lund 1650 Explorer.

Fishing Junky , The Outboard is mounted through the top hole so the motor is set as low as it can be the cavitation plate is at least two inches below the bottom of the boat when the lower unit is trimmed down until it contacts the stops, This puts the back of the plate much lower than the bottom of the boat !
Interesting note is that the boat came with a two stroke and the shop had to do a motor swap to give me the four stroke I wanted. Looking at the motor mount it is obvious that the two stroke motor was mounted two holes higher on what ever boat they took it off of . To me two holes up would put the cavitation plate even with the bottom of the boat .

Sooo , I think I will raise the motor see what the RPM's do.

Thanks all !


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Klbowe, wow, I had a 1650 Explorer and I was doing 35 with a 40hp Suzuki 2 stroke and no load.

There is definitely something wrong there. It's a light boat, a 90 should make it fly.

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The motor is definitely mounted too low.
The cavitation plate is well below the hull.

I spoke with the dealer and they said that they always mount the outboards as low as possible . DUH

The plan is to borrow a cherry picker and raise the motor to the proper level then see what the RPMS , speed and handling go .

I will do it myself with some help from a friend rather than let the knuckle heads that sold me the boat touch it.

Thanks Again !

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I am confused!

I have a 16.6 ft lund with a 90 hp yamaha four stroke .

The dealer set it up with a 17 pitch prop and full of gas and two fishermen it runs 35 mph 5000 rpm .

Yamaha owners manual says the RPM's should be 5500 to 6000 when wide open .
And their prop charts and Mercurys prop selector put me in a 23 to 24 pitch prop .


If I increase the prop pitch from my 17 to what they recommend wont my rpms be even lower ?

Should I strive to match the recommended RPMs and lower my pitch or what ? ? ?


help !

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Something is wrong there. You may want to give yamaha a call and see what they say. Your RPMS seem very low for the current prop you are running.

------------------
Mille Lacs Guide Service
www.millelacsguideservice.com

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Be sure to coat bolts with silicone whe you re install them, especially lower 2, since they will be in water all the times, and you don't want to have leaks in boat.
Lund installs Teleflex gauges, you should be able to check yours or adjust it from idle, in back of tach there is a selector, you have to use a small screwdriver, and you can do it while motor is running, easiest way is to let it idle, and check if needle marks approx 600/700rpm, here's Teleflex support link (very good):

http://www.tflx.com/tech.html

[This message has been edited by Valv (edited 05-24-2003).]

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Send me your email and I will explain how to do it without a picker. [email protected] Junky.........

[This message has been edited by Fishing Junky (edited 05-24-2003).]

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Sorry to drag up an old post but I wanted to thank those who replied and told me what to look for .

The motor has been raised and that brought the RPM's up to 5000.

The boat really handles much better and now I think I will play around with the props and find one that works best !

Thats What I get for buying from a Boat Super Store .

A special Thanks to fishing Junky for emailing me a tip and instructions that allowed me to raise the motor mounting by myself .

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Your welcome kl. Glad everything worked out for you. Don't be afraid to drop down a pitch if your still not within the rpm range. Just make sure your tach is accurate. Junky..........

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