Another prop selection thread

[tramsdell]

First of all, what tach setting should a v4 evinrude be at? I think im way off. Currently running a 17p on an 18ft alum with 15 gal. Tank 3 batteries and 300lb of persons, and at wot my tach reports about 3200r which simply cant be... the thing is SCREAMING back there.

 

[Sea Rider]

The current tach came with the boat or bough one separately, that's a 2 stroke V4 motor ?

Happy Boating

 

[tramsdell]

The current tach came with the boat or bough one separately, that's a 2 stroke V4 motor ?

Happy Boating

The tach was on the boat with a merc 90hp. I bought the boat and put on a 2stroke 110 evinrude v4. I spliced in the tach harness but didnt change the tach setting because i have no idea what the setting should be

 

[jimmbo]

What brand is the tach? With that info, check to see if the manufacturer has a website, you might find what you need there

 

[Sea Rider]

Was the other 90 motor same 2 strokes one ? how many cylinders were there ?

Happy Boating

 

[tramsdell]

I dont know anything about the old motor other than it was a merc 90.

 

[tramsdell]

I got out yesterday and fiddled with tach settings. It looks like wot im hitting 6k rpm, which i think is a bit on the wrong side of things. My 19p is already ordered, that ought to get me down to 5800 right?

 

[Sea Rider]

If tach was adjusted well and now reading right, can't possibly reduce 200 wot rpm going + 2 sizes up with a new 19 pitch, expect to reduce way more, only a wot run as loaded will tell. Personally would have started with an 18 pitch.

Happy Boating

 

[WesNewell]

I got out yesterday and fiddled with tach settings. It looks like wot im hitting 6k rpm, which i think is a bit on the wrong side of things. My 19p is already ordered, that ought to get me down to 5800 right?

Going from a 17p to 19p should lower the rpm by ~400 rpm. But the very first thing you should do is check engine height. That can make a big difference in performance and max rpm. Still a 19p prop sounds about right for your setup not knowing the weight of the boat. Assuming the boat weighs 1200# dry you should see about 45 mph if the engines at the proper height.

 

[tramsdell]

Engine height should be good, cav plate is about even with maybe 1/4 inch below the hull. I do have an 18p on another boat , i may try that out. I went to 19 only because piranhas come in odd numbers only, apparently. If the 18 alum is perfect ill just toss the piranha in the boat as a spare and im sure the 17 will be good for tubing.

 

[QBhoy]

Sounds like your engine is on the low side by what you say above. Very unusual to have the cav plate below the hull line.

 

[tramsdell]

Sounds like your engine is on the low side by what you say above. Very unusual to have the cav plate below the hull line.

I can't tell if you're trying to be funny here.

 

[QBhoy]

I can't tell if you're trying to be funny here.

Hi. I wasn’t trying to be funny. Apologies if you thought I was friend.
Maybe I have you wrong but usually a well set up unit will have the cav plate at least in line with the hull or slightly above. Many variations depending on hull and even the performance intended. But usually the plate (AV) is considered well set up in line or perhaps even an inch or two higher on some faster planing hulls.

 

[QBhoy]

I can't tell if you're trying to be funny here.

Have a wee look at this. Good info here.

http://media.channelblade.com/boat_...s/dts/dealerlibraries/8441/copetipstricks.pdf

 

[tramsdell]

Ok, thanks mate. Looks like you're coming from a performance boating background. This is the important caveat from your link: "However, there are exceptions to the above. Many small fishing engines and some larger
engines are designed to run with their ant ventilation plate an inch or two below the boat
bottom. This can assist in reducing or eliminating propeller ventilation." I think on fishing boats flatout performance is sacrificed for ability to handle rough conditions.

 

[QBhoy]

Ok, thanks mate. Looks like you're coming from a performance boating background. This is the important caveat from your link: "However, there are exceptions to the above. Many small fishing engines and some larger
engines are designed to run with their ant ventilation plate an inch or two below the boat
bottom. This can assist in reducing or eliminating propeller ventilation." I think on fishing boats flatout performance is sacrificed for ability to handle rough conditions.

A fair and valid point. You’ll likely be spot on then.

 

[Sea Rider]

Post a side picture showing lower and upper plates while motor sits at 90º on transom. Motor/transom height talk will go on forever. Speculation is the mother of all vices.

Happy Boating

 

[tramsdell]

Tried an 18 pitch. Not where i need to be. 19 blades should be in by next weekend.

 

[tramsdell]

Finally got to try the 19p. Worked well, and with 1000lb of persons and gear i was running 5600r, so this is probly my best all purpose prop, although im gonna try a 21p if im solo it may be more apropriate.