posted 05-28-2006 04:28 PM ET (US)        

Got some negative comments about it Christmas time from some buddies with a 26-foot Grady. As if that could be compared. Ha. I told them to double the weight of the Grady and then come tell me how fast it planes.

Seriously though, I don't really think the acceleration is too bad with my current set up, which is a 1988 Johnson 40-HP on a CMC PT130.

However, I'm switching to a 1998 Honda 40-HP four-stroke and the posts here at CW seem to all agree that going from a two-stroke to a four-stroke is NOT going to help the acceleration. I'm not switching to a four-stroke thinking it will improve my acceleration. I'm switching for other reasons.

I plan on installing a Doel fin on the Honda. I put one on the Johnson and it made a world of difference for both time to plane and porpoising.

I am, however, hopeful that the following two items might offset the two-cycle/four-cycle disadvantages:

1. The Honda will actually be less weight on the transom than the CMC and the 88 Johnson.
2. The newer Honda, if what I've been reading here is accurate, should actually have more power then the older Johnson

So is there something else I can do to help the acceleration?

In reading several threads here, I've gotten the impression that there are stainless steel performance enhancing props that could help.

Tom Clark responding to the thread on Prop for 13-footer:
http://continuouswave.com/ubb/Forum4/HTML/004468.html
notes that there might be one out there that could help.

Has anyone been successful in improving their acceleration with a different prop in a 13-foot without killing their top end?

The Honda owner's manual says the gear ratio is 2.09, and the full throttle range is 5,000 to 6,000-PRM.

Thanks,

posted 05-28-2006 05:59 PM ET (US)            

Let me see if I have this straight:

For best high speed, prop so WOT is close to 6000, then back off 2" of pitch for acceleration.

So if 10x13 gave me 6000 RPM WOT, to get improved acceleration I should drop back to 10x11?

posted 05-28-2006 06:56 PM ET (US)            

Top speed may or may not occur at the very top end of the WOT range. Most outboard motors have their power rating right in the middle of the WOT RPM range but we like to see motors that can spool up to the upper half of that range in general.

If you can just hit the redline when the boat is very lightly loaded, that is great because when it is loaded down some more the motor will still be within its normal operating range.

It is OK to drop down to a pitch that will allow the boat to exceed it redline with a light load if you are going to be using the boat with a chronically heavy load, such as waterskiing, much of the time. A 2" drop is a bit excessive for a 13 footer. A 1" reduction in pitch would be better.

But all this assumes you already know how you new motor will perform, and you do not yet.

As to what propeller to try first, I suggest you try whatever your dealer suggests. Get the motor broken in and then do some speed trials. Note the top speed and the maximum RPM the motor is able to achieve.

Most 13 footers will turn a 13" pitch prop and I would expect your boat to use one too. You have to have some baseline data before you can really dial in the perfect prop.

One thought I have to help your acceleration goal is to try a four blade propeller. I do not know of any stainless steel four blade props to fit your new Honda 40, but Honda (or Solas, Honda's supplier) makes a nice aluminum prop that comes in 1 inch increments of pitch which would make dialing the best pitch quite easy.

posted 05-29-2006 02:46 AM ET (US)            

Thank you for taking the time to lay the idea out so well.

I had not considered the effect weight has on max RPM.

Here's the plan then:

1. Use the dealer suggested prop (likely a 10x13). Gather some data on RPM and speed at WOT, with a lightly loaded boat.

2. Best 'all around' prop should see WOT between 5500-6000, hopefully nearer the 6000 mark.

3. A prop for waterskiing and heavy loads will then be 1" less pitch (likely a 10x12).

But - won't know until it's tried on the boat. I can't wait!!!

Perry:

posted 05-29-2006 02:57 AM ET (US)            

I mis-read your comments about 4 bladed props, thinking there were not any. On re-reading I see my mistake, and see that there are Aluminum 4 bladed props available.

Do the 4 bladed props give better all around performance, or do they tend to lean towards either acceleration or top speed?

Thanks again!

posted 05-29-2006 08:11 AM ET (US)            

You anticipate that the four-stroke HONDA motor will not be able to accelerate the boat as fast as your existing two-stroke JOHNSON. This prediction may be reasonable. The acceleration of the two-stroke may be better because it can produce more torque at lower engine speeds. Ultimately it is torque which turns the propeller and moves the boat.

By reducing the propeller pitch you can reduce the amount of torque needed to turn the propeller. This will help the engine be able to accelerate and spin up to a higher RPM where it can begin to develop more horsepower.

posted 05-30-2006 03:43 AM ET (US)            

Thank you for the summary. I'll go see if I can find a comparison of the Torque profiles of the two motors. That should be interesting to compare.

Tom:

Thanks for the info on the 4 bladed props. Sounds to me like I should expect a 4 bladed prop to have a similar effect to dropping the pitch of the prop?

The prop choices seem to be a compromise, like most everything else. That's what seemed so interesting about the new Mercury ENERTIA props. Sounded like they were boosting both acceleration and top speed. Because of a lighter and stronger metallurgy? Not available for a 40HP though.

Does a composite prop also give a similar all-a-round boost?

In searching on props, I came across Piranha props. They sound interesting too. Light weight, thinner material. I would think these must help with torque.

However, I live on a tidal creek with very low tides and oyster beds. I think replacing composite props could become quite expensive.

posted 05-30-2006 04:10 PM ET (US)            

Yikes! Well that answers THAT. Thanks for the heads up. Although even if they worked well I think I'd be worried about trashing one every time I came in or went out near low tide.

Perry:

Thanks for the link to the Honda site. I was wandering around the site on Sunday and could NOT find the props!

posted 05-30-2006 04:52 PM ET (US)            

OEM 3 blade props:
11 3⁄4 x 10
11 1⁄2 x 12
11 1⁄4 x 13
11 1⁄2 x 14

Solas 3 blade props:
12 1⁄4 x 7
12 1⁄4 x 8
12 1⁄8 x 9
11 5⁄8 x 11
11 3⁄8 x 12
11 1⁄8 x 13
11 1⁄8 x 14
11 x 15

Solas 4 blade props:
11 7⁄8 x 9
11 3⁄8 x 10
11 1⁄8 x 11
10 7⁄8 x 12
10 1⁄2 x 13
10 1⁄2 x 14

All these are aluminum, with no stainless steel listed. But a large selection to make me confused, none the less. Taking the Dealer's advice and working from there appears to be VERY good advice.

Do Mercury props also fit this motor? I've read that Honda uses a Mercury lower unit?

posted 07-30-2006 09:41 AM ET (US)            

First off, I'm VERY happy with the acceleration. She just JUMPS up on plane now. Even with 3 adults. Not something I really expected, but I'm happy to report! The boat does NOT feel anywhere near as fast as with the old Johnson and CMC PT130 though. The boat is also MUCH easier to handle and control.

My impressions with the CMC+Johnson were more like a racehorse wanting to bolt. With the Honda it's far more like a sure but steady ride. Far easier and smoother to accelerate or decelerate. Huge difference in performance. Better? Hmmmm. Depends on what you want. The Johnson was a rush. The Honda is a pussycat.

Rigging was as follows:
- Motor installed with cavitation plate about 1 1/2 inches above bottom of transom
- Combined tachometer and hour meter installed
- Doelfin installed

I still have some tuning to do though. And could use some advice.

The dealer put on a new 11 1/8 x 13 prop, and I have the used 11 5/8 x 11 prop that was on the motor when I bought it. It appears to be in decent shape.

When I tried out the boat with the 13 at WOT I could only get to a tach reading of 41-4200 rpm. At WOT something 'odd' occurs. I'm having a hard time explaining it. It almost felt like the prop broke free, if that makes any sense? But the tach does not jump up or anything.

I switched to the used 11 prop and was able to get to 45-4600 rpm, but had the same 'odd' feeling and sound to the motor and prop.

The motor is supposed redline at 6000 rpm and have an internal 6200 rpm governor/cut out. The engine sure SOUNDED like it was wound out, but the boat was not developing anything approaching the speed of the Johnson.

Could the tack have been installed incorrectly? How can I tell if the tach is not set up properly, i.e. not reading the correct rpm's?

Could the engine be mounted too high and I'm grabbing air at WOT? What should I be looking for to tell that?

Any recommendations would be greatly appreciated!

posted 07-31-2006 11:51 AM ET (US)            

I did not have a tach with the Johnson. I had the dealer install one with the new-to-me Honda. It's a Honda tach. And I don't have a speed measurement. It's on my list, but I'm currently in Dublin, Ireland through the end of August so it will be September before I get to play with the boat again. I'm trying to line up all my ducks so I can get it resolved as soon as I can on my return. Wilmington, North Carolina is beautiful in September and I don't want to miss another gorgous month.

Both Honda props are aluminum. The motor does have power tilt and trim and I was tilting it up to where it would start porpoising to try to get the most speed/rpm. The anti-ventilation plate is about 1 1/2 inches above the bottom of the transom. Could be a tad more. I eyeballed it, but did not measure.

How do I recognize a prop breaking loose? I would have expected to see the tach spike upwards? But it did not. That's what is making me think the tach is set up wrong and that I'm perhaps hitting the internal governor limit of 6200 rpm?

posted 07-31-2006 12:00 PM ET (US)            

I'm very happy with the acceleration at the moment. The boat literally jumps up on plane with three aboard. But I've lost a lot of 'perceived' top end speed. I'm in the market for a combined GPS/Fish Finder so I can get a real reading of speed. But in the mean time, I'm trying to get this new set up tuned as well as I can.

You might be right about the more horsepower. But the additional weight of a 60-HP or 70-HP starts causing other problems. I have read several threads here on CW of folks running larger motors on their 13-foot boats. They all seem to agree that with the horsepower comes safety issues, but that the extra speed and horsepower are fun.

I'm torn between wanting speed and a smooth ride. The Honda is providing a much smoother boating experience. But the 'giggle' factor of the higher speed was lost.

Just proves that everything is a compromise!