Honda 50hp, speed / prop

argonaut · Post by **argonaut** » Wed Apr 05, 2006 6:13 am

I bought my 97X used. Since I've had it the engine's run about the same, which is to say it'll push me at about hull speed but not a lot more, maybe 8-9 kts.
Since lots of things have needed fixing and I mainly sail so I haven't bothered with the engine much, but this boat should go 15mph with a 50HP Honda, don't you agree? The manual had "Honda 11 3/4 x 10" prop handwritten in it, making me think that's what is on it, but I've no way of knowing what the prop really is since the PO put it on. Also, I had to replace the throttle and tranny cables, both had cracked where they exit the motor. I've noticed underway that the motor won't go over about 3200 RPMs, and that's about 8 kts, same before I replaced the cables.
Is this more likely mismatched prop, misadjusted throttle cable, or something else?
I've pulled cylinder plugs when running to see if any are dead and they are all working. With the throttle linkage off and ears on it will rev higher than 3200. That's with no load of course, but with the throttle linkage connected you can't open the throttle as far as it will go. Should the linkage be adjusted so the carbs are all the way open at WOT setting? The control is the Honda original side mount type.

Maybe it's time for a Yammie.

Terry · Post by **Terry** » Wed Apr 05, 2006 7:45 am

First thing I would do is take the whole rig to a Honda dealer and have a certified Honda mechanic service the engine. I have a 2003 Honda 50 and I get 5800 rpm WOT and when I put her in the water next week for the season's first I expect to hit 20 MPH not 15 mph. Of course it will be lightly loaded, no ballast and a freshly waxed clean hull. The dealer here usually puts a 3 X 12 X 10.25 prop on the Honda 50 and that gets it into the 5500-6000 rpm range. I use a solas 4 X 11.4 X 9.5 and I get good performance from it, if you should ever decide on a 4 blade prop go for the 4 X 11.8 X 9 Solas, it should put you right in the groove. If you are not getting 5500 RPM or higher something is not right. I am not mechanically inclined enough to know what it is but common sense dictates something is wrong. Even at the end of the season heavily loaded with an inch of growth on the bottom I still got 13 mph, get the engine serviced.

Paul S · Post by **Paul S** » Wed Apr 05, 2006 7:58 am

lightly loaded I have hit 17 mph (gps speed). Fully loaded, maybe 12-13mph on a good day. It gets to WOT without a problem.

Other than winterizing, I, personally, have not really played with my motor. The honda dealer has (not impressed with their service)

Paul

elia · Post by **elia** » Wed Apr 05, 2006 8:24 am

I have a Honda 50, and initially had some problems with my motor not making the rated RPM's. After some research I found that the problem was due to the pitch of the prop. Once you decide how you want to use your boat the following links will give you all the information you will need to select the correct prop.

http://www.deltaprop.com/linkso.asp

http://www.kencook.net/Setupart.html

http://www.caravelleboats.com/propeller%20info.htm

http://www.indoorduration.com/propcalc.asp

Luke · Post by **Luke** » Wed Apr 05, 2006 1:34 pm

Argonaut,

BTDT with my Honda 50.
Now that you have rebuilt your carbs,
I am 90% certain that your current problem is the prop.
Look closely at the prop.
You should be able to make out the part number.

Your motor came stock with a 13 pitch prop.
You need a 10 pitch prop to get the rpm's up to 5,800.
With the 10 pitch you will see at least 15-17 mph lightly loaded,
with a clean waxed bottom in smooth water.

Luke
1999 26X
Honda BF50HP

Sailing out of West Palm Beach, Florida

crick · Post by **crick** » Wed Apr 05, 2006 4:03 pm

I had a similar problem with my Honda 50.
The throttle cable was not correctly attached.
For a dealer it should be a simple fix.
Crick

Dimitri-2000X-Tampa · Post by **Dimitri-2000X-Tampa** » Thu Apr 06, 2006 7:51 pm

Argo, if your throttle cable is right, then when you push your throttle lever all the way open, the carbs should all be completely open or very close to completely open.

The other thing you could check for is if one cylinder is missing. If thats the case, probably one of your sparkplug tips will be much darker than the other three. The key here is if you see one plug looking different than the other three.

If you are over propped (which is the most likely cause if your engine is running right), then there is going to be a very deep throaty sound coming out of the carbs. If it doesn't sound like that, then there could be something else limiting the RPM or it could be the throttle cable not opening the carbs all the way.

argonaut · Post by **argonaut** » Fri Apr 07, 2006 10:34 am

Argo, if your throttle cable is right, then when you push your throttle lever all the way open, the carbs should all be completely open or very close to completely open.

I checked by pulling plugs and all cylinders are firing, haven't done this over 3000 rpm though.
I also checked the prop and it says 11 3/4 x 10 right on it, so I think that's the problem less now.
Tonite I'll open up the control box, I really think something in there is limiting the distance the throttle cable will move. Now that I've heard that the plates should be able to open completely I can take a look a t that this weekend... supposed to be blowing 15-20 kts anyway.

Captain Morgan · Post by **Captain Morgan** » Fri Apr 07, 2006 4:16 pm

you could do a simple power balance test to see if all cylinders are firing

argonaut · Post by **argonaut** » Sun Apr 16, 2006 5:54 pm

Update on the throttle situation.
I adjusted the throttle linkage and cable per the manual, There was excessive free play in the cable, making opening up the carbs all the way impossible. Then gave it a test this weekend on an overniter.
I'm still mainly a sailor but coming back I raised foils and opened her up a bit to drop the ballast & see what effect the adjustments had on speed/rpms.
Now I -can- manage to get RPMs in the 4 to 5 K range.
In that range though there is an intermittant noise that makes me think the prop is slipping, kind of short bursts of higher engine speed so since the original aluminum is pretty beat up I'll be replacing it, maybe like Terry's Solas 4 blade.
At least 5K is in my rpm range now, think my speed was 11kts. Not where it should be but an improvement. My hull still has sticky bottom paint on it too, bet that's slowing things down a bit.
Thanks for all the good the pointers folks!

Timm Miller · Post by **Timm Miller** » Mon Apr 17, 2006 4:52 am

A crusty bottom will make for a slower boat.......your WOT rpm range for the Honda is 5500-5900 rpms.

Bill at BOATS 4 SAIL · Tue Apr 18, 2006 6:56 am

If the boats bottom is also crusty that will affect the boats speed.

argonaut · Post by **argonaut** » Mon Apr 24, 2006 2:15 pm

Yeeha!
Got the new prop... an 11.4 x 9 pitch Solas. Removed & replaced w/original prop nut, no shear pin though. I think I should pick up a spare just in case...

Terry · Post by **Terry** » Mon Apr 24, 2006 3:08 pm

Argonaut:
The Solas 4 X 11.4 is a 10 inch pitch prop, the 9 pitch is 11.8 diameter, which one did you get, 4 X 11.8 X 9 or 4 X 11.4 X 10?

argonaut · Post by **argonaut** » Tue Apr 25, 2006 8:51 am

details, details.... As my mate would say, "I don't know. It's white."

It's 9 pitch, 11 4/5" or, 11.8", which ever you prefer... 4 blade.

Link

MacGregorSailors.com

MacGregorSailors.com

Honda 50hp, speed / prop

Honda 50hp, speed / prop

Honda 50

Bottom

Which one?