Prop advice needed Yamaha 140 V4

[kenneth80]

Hi all.

Just bought a Yamaha 140 HP V4 from late 80`s since the 90 HP Force was crap and way underpowered. Unfortunately the Yammi didnt come with a propeller so im trying to figure out which one i need for best performance. You can see the boat by clicking on this link http://www.finn.no/finn/boat/object?finnkode=18198683.
I posted this link in the boat discussion forum to see if anyone know what boat it is since i dont know the brand and so if you have any information on that also i will be grateful.
The boat is 18 feet long and I guess the boat weighs about 1000 kg and i am using it in salt water.
What should the RPM at WOT for this engine be?

Kenneth

 

[steelespike]

Re: Prop advice needed Yamaha 140 V4

My 89 aftermarket service manual doesn't list a 140.Unfortunately
doesn't list by year. The 130 is rated at 5,800 I would think a V4 140 would be about the same.I'm not an expert and based on your somewhat sketchy info I would suggest a 17" pitch prop It may be a little underpropped but your better off under than over.You can use the 17 for tests to establish base line specs.we need present max rpm and speed in mph by gps if possible, with a typical load.Try to find a dealer that will let you test for the best prop.
Begin by setting up the motor with the antivent (cavitation)plate just above the prop even with the bottom of the boat. you may endup raising it after tests.

 

[kenneth80]

Re: Prop advice needed Yamaha 140 V4

Cheers Steele!

I live in Norway and i think the 140 is a non-US market engine based upon what i have read. Also hard to find specs on the motor..
I havent got a tach for the engine so it will be difficult testing. Is there any shortcut for measuring RPM? Isnt there a tool you can attach to the flywheel? Since it is winter in Norway i dont get to test the boat on water
Or maybe i should just force the freezing wind and have a go Having a HARD time waiting for spring! Went to a boatshop today and they seem willing to let me test some propellers but they said they only have Mercury propellers. Will they fit?
Cavitation plate is about 1 inch above bottom of boat. Seems OK?

Also i can add that i am looking for best top end performance and enough power to shuffle this heavy ho and if possible have a fuel efficient engine. Out of hole is second-rated.

Have a nice weekend all!

 

[steelespike]

Re: Prop advice needed Yamaha 140 V4

Try looking up merc and Yamaha props at the iboats prop store see if the numbers and or hub adapters match.Check out the tiny tachs they have a web site.
about $40 and easy install.Of course shipping may be a problem.
Without a tach there is no way to be sure you have selected the right prop.
If the merc props fit that dealer may let you borrow a shop tach for prop testing.You want the motor to be at lerast at its rated rpm 5,800
Generally a 4 blade will improve low end performance and mileage at a slight sacrifice of top end.