Pascal Larocque
New member
I know that some posts have been made in that subject but i thought that we could share a little of what we have been experimenting.
Just to put you in situation, the places we wanted to hunt where remote large marshes. But to get to theses marshes, open water was to be crossed. I felt that the best one man boat to handle this task safely were bbsb’s. To get out of the crowd and be were the ducks really wants to be, a mud motor would be the tool. Those 2 things were not designed to be matched. A shallow water motor on a hull designed for heavy seas is somehow a mismatch but I have felt safer in waves than I would have with a john boat of the same size plus they (the hulls) draft less water than mud motors need to operate.
As it is written in this post, http://www.duckboats.net/cgi-bin/forum/gforum.cgi?post=27982;search_string=mud%20motors;#27982
For the one man sneaks boats, there is really only one size of mud motors that are light enough to be used. And they are the 5 to 6.5 hp mini longtails; Scavenger, Mud buddy, beavertail or stump jumper are all less than 80 pounds. (Theses weed eater models that some guys are making are even lighter but I have never seen one running.)
. These motors have 3 major drawbacks
1: they’re not the best in rough seas
2: they are higher than regular outboard, not really suited for gunning over the stern bbsb style.
3: they have a low power to weight ratio when compare to regular outboard
Let’s look at theses problems one at the time.
1: they’re not suited for rough seas
It is true that in waves, the long handle moves up and down because the cavitations plate always keeps the prop just a few inches below the surface.
The only way to avoid the on power- off power you will get when the prop gets out of the water is by pulling on the handle, forcing it deeper.
It can be tiring on longs runs especially because you are sitting.
The limit will dictated by the motor, not the hull. If a guy wants to hunt the marsh and the open, he needs 2 motors.
2: they are higher than regular outboard, not really suited for gunning over the stern bbsb style.
What my partner has done on his was to remove the gas tank, install a pulse pump (diaphragm pump) and run a regular outboard gas tank.
Plus he made his own long tail and he designed it to have a much lower profile.
3: they have a low power to weight ratio when compare to regular outboard
This is the part on witch we worked to improve and wanted to share the info.
Mud Buddy do modify their engines to gain h.p. But only their big one has access to hop up kit.
John fond out that Karting guys are modifying the same little motors that are used on small MM. Honda engines (gx160 and gx200) being widely used.
The places to find the most info are:
· Nr Racing site http://www.nr-racing.com/
· This article from http://www.kartingtechinfo.com/
as a good step by step explanation. Plus a list of parts numbers.
http://ckranb.tripod.com/GXsite/GFRT_tech.htm#Race%20prep%20your%20Honda
· Go cart forum: http://karting.4cycle.com/forumdisplay.php?f=71
· And 4 stroke.com for good explanation on jetting http://www.4strokes.com/tech/
The modifications we did are mostly bolts on, without machining needed. Plus, put aside air filter and exhaust, most parts are Honda.
This is what I have done on my motor.
1. Change valve springs to stiffer one:
2. Change exhaust for a less restrictive one: I would not recommend the one designed for karting for they are to loud to be used in a marsh. We used motorcycles one and are happy with the noise reduction and the exhaust flow. Make sure you have at least 15 inches of 1’’ headers tubing before the muffler. (it will help low hand torque)
3. change intake to a less restrictive one:
4. increase ignition timing: change the woodruff key that hold the flyweel
5. rejet the carb: if let the way it is, you may damage your engine because the mixture will be too lean. The color of your Spark plug wills tells you if you have the good mixture. Good explanations on how to read the spark plug are available at 4stroke.com
6. Add a tachometer: you need it to adjust your governor and with the hours counter, it will tell you when the oil change is needed.
7. Adjust governor: (do not disable it like they do in karting, a mud motor need this security, rev limiter, when the prop get out of the water.) Instead, change the spring to a stiffer one (Honda part 16561-ZE1-020) that will give you the desired rpm. I have set mine to limit the revolution at 4750 rpm.
In part, It will cost you around 250-300$
You will get around 9 hp and 4750 rpm from your 6.5 hp GX200. It equals a nr racing stage 1 mod that is really reliable.
On the true race engine, the one that are not reliable; they get up to 20 hp from them a GX200 (Honda 6.5hp)!!!!
You will maybe have to change the size of your prop. Rpm will tell you. I run a 7X4 mudbuddy on mine. It limits my rpm at 4000. At first, I have tried a 8X4 and I could not get more than 2900 rpm.
One last thing, a 9 hp Mud motor will not compare to a 9 hp outboard. (Outboards are rated at the propeller and MM are rated at the motor). But these modifications can help narrow the gap.
After having ridden our mm for a year now, here are our thoughts
1: they are the sweeeet in the marsh… and under certains conditions; they team very well with bbsb’s.
2: The added hp were useful when plowing thru thick cattails
3: Their handle is about just the right length for my wigeon. No need for a tiller
4: next year, we will have regular outboard for theses more open water hunt or when the marsh will be frozen.
It may not be a conventional bbsb Set up, but It worked for us.
hope to help some of you
Jonathan gagné
Pascal Larocque
