OK I am still confused on the prop/engine

thataway":2huiwobl said:
Then I would suspect that there is an issue with the way the motor is mounted. ... If your Permatrim is not running on the surface (which I believe you said it was not), then the motor is lower than ideal.
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That is the case, and I suspect the same as what you say (I think it may have been your link that had the photos of the correct height).

Interestingly, I have been looking at where the four transom holes are on a number of 22 Cruisers. They all seem to be in close to the same location - so perhaps there is some "usual" guideline for where to put them. However, the "hole heights" used on the engines vary. For example, mine is set in the second hole down from the top and there are four adjustment holes. So I could raise my engine two holes (and probably will).

Theoretically the holes in the transom could be slightly higher, but not very much because the washers/backing plate on the inside of the transom would come up over the top edge.
 
13" pitch 3 blade props are common on 22's with twin Honda 40s for low altitude use. They let our 40s rev to 6,000 rpm which is ideal.
I tried raising my engines to get the anti ventilation plates out of the water while on plane but it really limited the amount of trim I could on the engines. Any small (very small) gains in speed weren't worth it.

Question. How much would the pitch need to be reduced when going to 4 blade props with an eye on trying to encourage stern lift? Or is this just foolishness with a 16 knot cruise speed?
 
Chester":2w0mylbi said:
13" pitch 3 blade props are common on 22's with twin Honda 40s for low altitude use. They let our 40s rev to 6,000 rpm which is ideal.
I tried raising my engines to get the anti ventilation plates out of the water while on plane but it really limited the amount of trim I could on the engines. Any small (very small) gains in speed weren't worth it.

Question. How much would the pitch need to be reduced when going to 4 blade props with an eye on trying to encourage stern lift? Or is this just foolishness with a 16 knot cruise speed?
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You want the anti ventilation plate/foil, just on the surface of the water, not out of it--and a lot depends on the dynamics of the water flow off the transom.

One inch pitch reduction is suggested for a boat going from 3 to 4 blades.
However, There are some good 3 blade stern lifting props. If I was going to explore this, I would contact Ken at Prop Gods. Prop Gods has a forum, and it is good reading.

http://www.propgods.com/forum/



Often similar questions are asked at The Hull Truth, and Scream and Fly forums..

A comment from Ken on one of the forums: "Blade design and geometry plays a very large role in the way a prop carries the boat. Its not just the number of blades….
When we wrote the FAQ section, its basically just "general" answers for most conventional boats.
In reality, every setup is different, and the characteristics of certain props can vary depending on the setup and what your comparing it too."

Going to SS speciality props can be expensive, and there may not be a lot of change for a bunch of $$$. It sounds as if you are fairly well dialed in--especially in relation to what ranger is experiencing. Back to the axiom that pitch is not the entire issue. First the boat has to be right, then the motor position/trim has to be right, and finally the prop.
 
Thank's, Bob. I worded that poorly, should have said the motors were raised one hole to get the AV plates out from under water while on plane.
The AV plates are the same height as the hull bottom now (again) and removing the wedges haven't caused any issues so far.
 
I have gwin 40 Hondas. I recently bought two new props and had the old ones tuned up.
They are the same size and pitch, but the new ones are a bit slower than the old ones.
I have put the old ones back on and am saving the new for spares.
Jerry C Nile CD22
 
jerry97230":25crj8k4 said:
I have gwin 40 Hondas. I recently bought two new props and had the old ones tuned up.
They are the same size and pitch, but the new ones are a bit slower than the old ones.
I have put the old ones back on and am saving the new for spares.
Jerry C Nile CD22
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Jerry are these the same manufacture and model number? Or just the same diameter and pitch? Any chance the "old" are a smaller diameter (like with a file?)…I had to file the edges of the prop which was on my boat when I purchased it. It is now our "spare" --the new prop is the same dimensions, but the cup is slightly different.
 
Ok got to use the boat for the first time today. 7 hours on the water, discovered different things about my motor prop combo.

With the newly painted bottom in about 5 to 8 knots of wind I put her through the paces.

At WOT I was maxing at 5200rpms. I was getting 19.5 average and occasionally 20 Kmph. (the water was never a smooth surface and there was a large flood with current surface action)

I found that at about 4200 to 4400 rpm (my favorite speed) I was getting between 14.5 and 16.5 Kmph

In some tidal rips I needed to back off to about 3000 and 10 Kmph to deal with the banging from the waves.

These speeds were SOG by GPS. I have an impeller on the stern but I cant find any gauge or setting on the C80 to show speed over water.

All in all I was happy. Maybe a 3 blade prop may allow a higher rpm getting to the magical 6000 but I doubt I will run her at WOT very often anyway.

I was quite happy at 4400 and the 16 Kmph. The engines sounded sweet at that running.

Thanks all for the discussion. It helped me understand more on my first drive.
 
Just my opinion, but I would change props, to get the engines close to the 6,000 RPM--that is 800 RPM below WOT max.

Were the speeds an average of against and with the current?

The tabs and plus permatrims help get the bow down to help prevent the pounding.

A little chop (6") does not slow down the C Dory--when it gets to 1.5 to 2 feet then it is significant.

With the same pitch you would get about 100 RPM more with the 3 blade-that alone would not be worth a change.

As I understand it, the boat has 11.5 D 10P. 4 blades currently, the other props he had were 10.5 D by 13 P . Most of the other 22's 40's are running 11.1x11. (both 3 and 4 blade), SS Solas, three blade, 12dx10p

T R Bauer didn't have the prop size, but: "My max rpm is really close to 6000 rpms and moves the boat a hair or two over 30 mph…. no trouble going 23-25 mph on flat water. I could have even gone faster without trouble, but don't like going past 5000 rpms in general."

It
 
rainger":33z5bgoa said:
Ok got to use the boat for the first time today.
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Sweet :thup

rainger":33z5bgoa said:
At WOT I was maxing at 5200rpms. ... All in all I was happy. Maybe a 3 blade prop may allow a higher rpm getting to the magical 6000 but I doubt I will run her at WOT very often anyway.
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The reason you want to hit the recommended RPM at WOT, is not because you plan to run at WOT. It's because, essentially, the engine doesn't have a transmission (i.e. multiple forward gears), and so if you are not at the right RPM at WOT, then you are lugging the engine at all settings (not just at WOT). WOT is just how you gauge the setup, and whether it is as recommended or not.

So, even if you never do anything but putt along, it's good for the engine to be able to achieve the recommended RPM at WOT. Then you are "in the right gear" for all of your running at whatever speed.
 
thataway":qjcoc9w9 said:
Just my opinion, but I would change props, to get the engines close to the 6,000 RPM--that is 800 RPM below WOT max.

Were the speeds an average of against and with the current?

The tabs and plus permatrims help get the bow down to help prevent the pounding.

A little chop (6") does not slow down the C Dory--when it gets to 1.5 to 2 feet then it is significant.

With the same pitch you would get about 100 RPM more with the 3 blade-that alone would not be worth a change.

As I understand it, the boat has 11.5 D 10P. 4 blades currently, the other props he had were 10.5 D by 13 P . Most of the other 22's 40's are running 11.1x11. (both 3 and 4 blade), SS Solas, three blade, 12dx10p

T R Bauer didn't have the prop size, but: "My max rpm is really close to 6000 rpms and moves the boat a hair or two over 30 mph…. no trouble going 23-25 mph on flat water. I could have even gone faster without trouble, but don't like going past 5000 rpms in general."
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My props are 11.25 x 13 with twin 45s. The motors are mounted on the 2nd hole from the top on the transom bracket if it matters. My size props probably have 10-15% too much bite for your application, which is why I didn't note it. Maybe not - it is a starting point.

You really want to strive for a 6000 rpm redline as these little overhead cam motors need a lot of rpms to operate efficiently. I don't run over 5000 rpms often for longevity reasons - just because it can run 6000 rpms doens't mean I am going to and mine have 2000 hours now running at very close to 5000 rpms.

Why doesn it matter???? Well, you really want the motors to have the correct amount of mechanical advantage they can for the purpose of efficiency. 4500-5000 rpms is a pretty light throttle setting in my boat - maybe 60-70 percent and 5000 rpms gets me 20-24 mph depending on conditions, load, and trim. My boat when trimmed right will achieve 4.5-5 mpg with a medium load. Also, heavy throttle settings at lower than optimal rpms cause the carbs (if you have them) to richen up and that extra fuel gets past your oil control rings. Guess where it goes? Into your oil thus dilluting it and changing its chemistry leading to premature wear and tear.

Bottom line: this is something you really have to correct.
 
I wanted to compare my boat with some of the others--moderate load, with one fuel tank half full, and the other only a few gallons, no water, 400 lbs of crew and skipper, (My son weighs 225, and I 175). Tools, and some clothes aboard. 2006 Honda 90 Carbed, with 13.5" diameter and 15" pitch Aluminum prop. Tests done at sea level in salt water. Boat bottom is clean, but has bottom paint which is smooth.

Top speed was at 5800 RPM and (Measured on two Garmin chart plotters, no current, and about 3" chop) was 28 knots (about 32 statute miles per hour). I dropped the boat down to about 4200 RPM and 14.9 knots trimmed for the best speed at 4200 RPM. (set throttle, and trim tabs near neutral slightly down, with port slightly more to compensate for more weight on the port side), and outboard trimmed about 2/3 way down. By dropping the motor trimmed all of the way down, I lost almost one full knot of speed from 14.9 to 14 knots Trimming the bow down further with the trim tabs, I lost another 0.8 knot. This verifies my experience that the boat runs best at about 2/3 down trim on the outboard and trim tabs near neutral, and substantial loss of speed with both trimming the motor down to the max and even more loss of speed trimming the bow further with the trim tabs. I did this with several different planing boat speeds, and lost at least 0.8 knots each time. No fuel burn since do not have a fuel flow gauge on this 22. My best guestimate for fuel consumption was about 4 miles per gallon, but it could be slightly less at 15 knots. This is for my boat, with a Doelfin (what the boat came with) running just on the top of the water. Obviously others will vary.
 
Ok I have taken in my Michigan Wheel Vortec 11.5 x 10p x 4 props into a guy who magically changes them into different props. He is going to keep the cup but move the pitch to 9.

Also they will be tuned, blasted and repainted nice and new. I will be putting them on my BF40a twin Honda's in the next couple days.

I hope to get the boat into the water in the next week or so and if I can get a calm day I will put her through her paces to see what has happened to my RPM's boat speed etc from where they were.
 
colobear":2uki81ec said:
No...it means that the single 40 will still get to 5400 (or so) RPM but it will not plane my 22, that little engine and prop just doesn't have enough ooomph to do that. I have experimented and the one 40, at WOT will move the boat (heavily loaded) at about 10 to maybe 12 kts, not quite on plane. But, that is way too hard on the engine and I would not do it. The engine will move the boat comfortably at 8-9 kts at 4200-4500 rpm. I have tested that in a real world situation when the starter solenoid failed on one engine and we had to use the other one to go several miles to port.
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Just to thrown in a wild card--I have seen this discussion surrounding the 16 ft Dory go on and on too. And, top speeds from 18--30mph WOT discussed and agonized over. However, I found nothing difficult here. My Honda 50HP 2003 that I run recommended 11.1 X 13 DP so that's what I tried with this engine. At WOT-- I was at 6000 RPMs-- GPS speed at 30.5 MPH.
As far as trim-- I started trim "full in" until it was peaking out at 28 mph - then clicked out a little positive trim, got 29 MPH another click 30MPH - one more click 30.5MPH, which peaked at 6000 RPMS and that was as fast as that boat will handle without getting squirrel.
Maybe the factory knows something --eh
 
Ok I put on the new props this weekend and took her out for a short run. I was in about 8k of wind with a low chop. The new props. Honda 12.1x9x3. (Remember I don't have trim tabs)

Now I assume that the engines have governors on them and that they wont go over 6000 rpms notwithstanding what the tach says. One tach moves around with tapping on the screen.

So My WOT with my old props was about 5200 then I changed their pitch from 10 to 9 and my rpm WOT went up to about 5400. My old top end speed use to be about 18 knots or about 21mph.

My new props WOT showed my tachs at 6200/6300 I am assuming an error in the tach, however with not flat seas I was getting 21K or about 24 mph.

So at 4000 rpm I was 11K at 4400 = 13.5K, 4800/5000 rpm around 15.5K.

Boat is fully loaded (fishing stuff, bbq, etc) and both fuel tanks are 2/3 full.

So it appears that my WOT has gone up about 3K but my cruising speeds now need about 400/600 rpm more to get the same speeds as before.

What I don't know is what my gas consumption will now be to run the engines at around 4800 as opposed to running them at about 4400 before for a cruising speed of around 15k.

But I am through screwing around with props and will settle in and see if I can figure out what my fuel consumption is.
 
I have only owned single engine C Dory 22/25's, so with twins, there are gong to be some differences. I do believe that the C Dory needs both trim tabs and Permatrims to get the best ride/speed. (Fun to spend other folks' money!).

It will probably not make much difference in top speed. But, with 80 hp, you should be going a bit faster? We do have 90 hp, single, and our "loaded" is with cruising gear for a month usually--pretty heavy--well over 1000 lbs plus of extra gear (ice chest, full, freezer, 3 AGM batteries, generator, food for a month, extra 5 gallons of water plus full water tank etc)--and we make a little more speed than you do.

It might be interesting to weigh your boat next time you have a chance,--if that is possible up there..

Generally I like to keep cruise speed down in the 4500 RPM range--again going to single engine. I rarely take up over 5000 RPM. Then only for very brief periods. The fuel burn will be similar for the same speed. at 4400 and 4800. It will be a little easier on the engine with the lower pitch prop.
 
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