Add cup, or more pitch, or go stainless?

[EricR]

I have a 15' vee hulled runabout, a 1969 Glasspar with a constant vee (don't know the deadrise angle exactly) and I am running a Honda 45 on it.

The engine has the standard equipment 11 //4 X 13" pitch three blade aluminum wheel on it. The cav plate is even with the bottom of the hull, there is no spray.

With two passengers or for that matter four, the thing turns 57-5800 RPM wot, speed is 29-30 mph depending on wind etc.

Honda specs 5000-6000 Rpm wot for this engine.

Should I:

1. Buy a 14' pitch three blade aluminum?

2. Have cup added to my current prop?

3. Buy a stainless prop of the same pitch as I have now?

I would like to get the RPM closer to 5500 and pick up a little bit of speed, I realize 1mph may be all I get.

 

[Silvertip]

Re: Add cup, or more pitch, or go stainless?

[QUOTE=I would like to get the RPM closer to 5500 and pick up a little bit of speed, I realize 1mph may be all I get.

Honda specs 5000 - 6000 RPM and your engine is turning 5800 but you want it to turn 5500. Your existing setup is almost perfect. Why would you want to decrease RPM to 5500 rpm and lug the engine?. Engines don't like that. Adding pitch and adding cup will indeed decrease RPM but it will likely not increase speed since it takes more power to twist that increased pitch or added cup so it may actually slow you down. I guarantee it will really slow you down when heavily loaded.

 

[EricR]

Re: Add cup, or more pitch, or go stainless?

Well it's just that I have been told by a couple folks I would be better off if it turned less RPM.

I work on marine diesels all day and believe me I preach getting it propped right. It's just that with diesels, they are rated a specific RPM, not "Yeah, get 'er within a thousand at WOT under load" like this Honda is. OMC's seem to be specific like 5000 RPM on the old V4's.

 

[Silvertip]

Re: Add cup, or more pitch, or go stainless?

Suit yourself, but when Honda says 6000 is the upper limit, the boat will perform best at that rpm. If you prop for the lower end of the band, any time you add more load than what you had when you propped for that rpm will kill performance and the engine won't like it as will be pulled off its power curve.

 

[Cricket Too]

Re: Add cup, or more pitch, or go stainless?

Is this a 4 stroke Honda or 2 stroke? I'm assuming 2 stroke by the given operating range. I wouldn't touch it, it sounds perfect right now. I don't know who is telling you to run it slower or why they are, but if it's a person that doesn't undersatnd that 2 strokes are completely different than 4 strokes, then don't listen. Dropping your WOT RPM is only gonna hurt every part of your performance, you might even end up burning more gas to do the same thing you do now.

I had a guy in a marine store actually tell me that 6000 RPM would kill an OMC V4, I walked out of the store.

 

[walleyehed]

Re: Add cup, or more pitch, or go stainless?

Cricket, I like that.....
7000+ hasn't hurt my V6 2-stroke yet....been there many times..and YES....stay at or as close to 6000 with the Honda with a normal load as you can....that engine is hurting at anything below that if propped for anything less at WOT.

 

[Crownie2]

Re: Add cup, or more pitch, or go stainless?

Is this a 4 stroke Honda or 2 stroke? I'm assuming 2 stroke by the given operating range.

I have never heard of a Honda 2-stroke. It is indeed a 4-stroke.

EricR - I also believe you are correctly propped now. If anything you might want to try a SS of the same pitch.

Bob

 

[EricR]

Re: Add cup, or more pitch, or go stainless?

OK folks I will try a SS prop of the same pitch- if I want more speed, I toss the little woman and those rugrats over the side! Yarr!!

 

[Cricket Too]

Re: Add cup, or more pitch, or go stainless?

Oops, even though I read Honda and typed Honda in my response, I had Yamaha in my head, sorry about that.