4200 rpm WOT

[shorenomore]

Okay, I got my prop (14.25 x 22 4 blade Stiletto Stainless) and mounted it to my 1991 Evinrude 155hp commercial. It is running 4200 rpm at WOT. My question to the experts is should I drop to a 20 or an 18 pitch. I am told operatingrange is 4500-5500 rpm and the test was w/ 2 people and almost no load. Your opinions are greatly appreciated.

 

[Hooty]

Re: 4200 rpm WOT

Hey shorenomore,<br />As a rule of thumb, 1" pitch = 200 rpm so based on what you've said, I would drop to a 18" and if ya have access to a 16", I'd try that.<br />I prefer operating the engine in the upper range of its rpm band. I have an old 200 hp 'rude that I turn 5800-6000 rpm (and it'll turn tighter) and it loves it. Keep us briefed.<br /><br />c/6<br /><br />Hooty

 

[Bob_VT]

Re: 4200 rpm WOT

4 blade is a real gripping prop. Usually the 4 and 5 blades are designed for heavier loads. Try a 3 blade IF you can borrow one. A 155hp should spin the prop you have at WOT w/o problem. Are you sure it is the prop???? If you borrow a smaller (lower) pitch this will help diagnose it better. Are your carbs opening all the way? I would check all these things before you invest $$$ in props.<br /><br />Bob

 

[round2it]

Re: 4200 rpm WOT

I was told by a dealer that when you prop a boat, it should be with one person, half tank of gas, and lite load. His reasoning was so u wouldn't over rev engine with a lite load. I was questioning my 200 hp, carbed motor. Only turning about 5400 or slightly less with 2/3 people with full tank of gas, 70 gals. I think I need to drop down in pitch altho he said I'm propped about right.

 

[shorenomore]

Re: 4200 rpm WOT

Thanks for the replies. I do plan on having much heavier loads (more people, tons of fish) but I wanted to prop it initially for the lightest I would normally be. I bought the 4 blade 22 pitch and I will be able to get one exchange. It almost sounds like I should go for a 16? As for the carbs, the guy I bought it from assured me it was linked and synched and I must admit it runs excellent from first turn of the key till I shut her off.

 

[shorenomore]

Re: 4200 rpm WOT

One more thing, how can I tell exact rpm? I bought a guage from West Marine and set it but the selector knob on the back seemed infinately adjustable so how do I know if I'm revving what I'm seeing?

 

[Beernutz]

Re: 4200 rpm WOT

I've been using Stilettos for years, and love 'em. Haven't tried the 4-blade variety yet, though.<br /><br />Stiletto uses a "progressive pitch" design technology, and it really works. When replacing a stock prop, I've had to drop as much as 3 inches on the pitch in order to get the WOT RPMs up to par. This results in amazing punch out of the hole, slightly higher mid-range revs (1-200), and much-improved throttle response throughout the range. They'll hold their bite better when jacked up and trimmed out, too.<br /><br />I'm fortunate to have a dealer who allows me to try out new props before deciding to keep them. It has brought him a lot of business, though.<br /><br />Hope this helps.

 

[Beernutz]

Re: 4200 rpm WOT

Oops, hit a wrong key. That should read as a 4-inch drop on the pitch.

 

[Dhadley]

Re: 4200 rpm WOT

Keep in mind that with a 4 blade prop you can run it much higher on the transom than a 3 blade. IE; raise your X dimension. You will increase your holeshot and top RPM. You wont get the 1500 RPM you are looking for but you will gain some preformance. <br /><br />Before you exchange your prop get an accurate tach. Stiletto props are great props but I think the diameter is 13 3/4 unless you have a Turbo (made by the same folks) which has a larger diameter. Both are excellent props.<br /><br />Good luck!

 

[shorenomore]

Re: 4200 rpm WOT

Dhadley, sorry for my ignorance, but are you saying that I can raise the entire motor on the transom to have less motor in the water? If so, how high can I go in relation to the bottom of the boat. What part of the motor should be even with the bottom of the boat?

 

[Dhadley]

Re: 4200 rpm WOT

Yes you can raise the motor on the transom. Usually with a 4 blade you can raise it so high you need a jack plate. Try raising it a little at a time and watch the water pressure. <br /><br />Good luck!