Author Topic: Mini Most XL Inaugral Test Run and Prop Selection  (Read 6938 times)

jmuskoka

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Mini Most XL Inaugral Test Run and Prop Selection
« on: August 09, 2013, 12:50:04 PM »
Whoo  Hoooooo!!!!!!   Whoo  Hoooooo!!!!!!   Whoo  Hoooooo!!!!!!   Whoo  Hoooooo!!!!!!   Whoo  Hoooooo!!!!!!   

Finally got my Mini Most XL in the water yesterday.  My 1985 50 HP Mercury has a few very minor issues, but nothing serious that can't be worked out with a bit of tinkering.   

Bottom line.......top speed on wide open throttle is 37 mph as verified on my GPS.   But here's the thing....I am pushing 6000 RPMS!  So here's what I am thinking.....I could easily throw a larger prop on the back with a steeper pitch.  Lower my RPMS to the recommended  5500 and gain top end speed. 

I pulled my 10 year old son around Kahshe Lake on an inflatable with my other son as a spotter and was still getting 34 MPH!   Lots of power!

I did have some water splash coming over the transom similar to Jim Butler and his post   here:  http://muskokaseaflea.ca/bb/index.php?topic=1250.0     (must be an XL thing).   Anyway....I raised the trim on the motor by one notch and that solved the problem.   It also increased by top end speed from 35 MPH to 37 MPH

On my final run with my brother things were going great for the first few minutes, then the motor just suddenly lost power and would not come back to speed.   Every time we increased the throttle the motor would stall as if it were being flooded.    At first we thought the timing or throttle advance might be off...but then why would it suddenly just go?  My pre-run check of the motor revealed a whopping compression of  160 lbs on each cylinder and great spark!  The only change between the first very successful runs and the final was I put more gas in the fuel tank.  My father suggested it might just be something as simple as water in the fuel system.

Any thoughts?

Can't wait to get back out on the water!   What a great first day!!!!!!


Here is a link to more pictures:   http://www.muskokaseaflea.ca/XLGallery2013/index.html

Chris






« Last Edit: August 09, 2013, 03:42:18 PM by jmuskoka »
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little boat

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #1 on: August 09, 2013, 05:27:20 PM »
Whoo  Hoooooo!!!!!!   Whoo  Hoooooo!!!!!!   Whoo  Hoooooo!!!!!!   Whoo  Hoooooo!!!!!!   Whoo  Hoooooo!!!!!!   

Finally got my Mini Most XL in the water yesterday.  My 1985 50 HP Mercury has a few very minor issues, but nothing serious that can't be worked out with a bit of tinkering.   

Bottom line.......top speed on wide open throttle is 37 mph as verified on my GPS.   But here's the thing....I am pushing 6000 RPMS!  So here's what I am thinking.....I could easily throw a larger prop on the back with a steeper pitch.  Lower my RPMS to the recommended  5500 and gain top end speed. 

I pulled my 10 year old son around Kahshe Lake on an inflatable with my other son as a spotter and was still getting 34 MPH!   Lots of power!

I did have some water splash coming over the transom similar to Jim Butler and his post   here:  http://muskokaseaflea.ca/bb/index.php?topic=1250.0     (must be an XL thing).   Anyway....I raised the trim on the motor by one notch and that solved the problem.   It also increased by top end speed from 35 MPH to 37 MPH

On my final run with my brother things were going great for the first few minutes, then the motor just suddenly lost power and would not come back to speed.   Every time we increased the throttle the motor would stall as if it were being flooded.    At first we thought the timing or throttle advance might be off...but then why would it suddenly just go?  My pre-run check of the motor revealed a whopping compression of  160 lbs on each cylinder and great spark!  The only change between the first very successful runs and the final was I put more gas in the fuel tank.  My father suggested it might just be something as simple as water in the fuel system.

Any thoughts?

Can't wait to get back out on the water!   What a great first day!!!!!!


Here is a link to more pictures:   http://www.muskokaseaflea.ca/XLGallery2013/index.html

Chris

 one word........VIDEO! :-D

Cubfan

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #2 on: August 09, 2013, 06:44:23 PM »
The fuel we are getting now is crap.  If you  look at the octane regular is now compared to when the motor was built we should actually be burning hi test.
My outboard mechanic also told me to be careful buying two stroke oil. The oils made by the engine mfg's include additives to help with the poor fuel we are now getting and that's why they cost more. I have been using the Evinrude/Johnson oil that is synthetic based- it is awesome. made my 15 much happier and quieter.

I had the same issue as you and shook the gas tank and it went away. I suspected water also. The engine would run but no power. I think shaking it put the moisture back into suspension in the fuel.  I am now adding sta-bil into my gas ( the new ethanol formula). The gas with 10% ethanol added we get here attracts moisture in the tank when stored
Cub Fan- Piper Cub that is !!!!!!

Jay Smith
Bradenton, Fl

jmuskoka

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #3 on: August 09, 2013, 10:13:48 PM »
I think you may be right!!!!!!  I am going to get some more gas...premium this time, drain the fuel from the motor and try again.  Thanks Jay....you're the second person who has told me this.

As for the prop and rpm issue...the prop that I was running yesterday was a 14" pitch.   I have another 50 HP with a few spare props and one was a 15".   Can't hurt to try and see what another inch on the pitch does for the RPMs and speed.   

Chris

« Last Edit: August 09, 2013, 10:17:10 PM by jmuskoka »
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dave freese

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #4 on: August 13, 2013, 01:17:22 PM »
Hi Chris,

I just had a chance to check out the photo gallery of your new boat, and WOW!!!  She is just gorgeous!!!  Absolutely fantastic job!!!  The brass hardware is a really nice touch by the way.

It was great to see you in Clayton a couple of weeks ago.  Too bad it was for such a short time though.  I really hope that lower unit works out for you.  Thanks again for all the swag!  I shall wear it proudly!!!!!!!

Dave

czysk

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #5 on: August 13, 2013, 10:48:56 PM »
Great looking boat Chris. I love the detail on the deck. Ethanol in the fuel is a real problem in my area, not only with moisture but it eats gaskets, fuel lines and the finish from the old cork floats clogging up the carburetor. Try to find some without ethonal.

Craig

thebarrett50.cal

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #6 on: August 14, 2013, 07:05:33 PM »
the fuel is basically poison for boats. the ethanol eats the insides of motors apart. my jetski just did the power loss thing 2 weeks ago, i put a new fuel filter and then bought a blue bottle of ethanol treatment which i forget the name of. hope its just a fuel problem

jmuskoka

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #7 on: August 18, 2013, 02:03:42 PM »
Here's an update.....

Got the boat out on the water for another run yesterday.   Re-checked the spark and compression.  Everything looked great!   Even replaced the plugs.   New gas with octane booster, so I know there is NO water in the fuel and I used another gas tank with a proven fuel line connection.  Motor started up like a dream and hit full RPM's in no time flat.   The pitch on the prop that I am currently running is 14" at 6000.   My 1964 Merc 500 has a 15" pitch, so I am thinking I could swap out the props.  Unfortunately the splined shaft is larger on the 1985 motor and they are not interchangeable.   I'm going to look for a 15 or 16" pitch prop and re-check the rpms and then I should be able to hit my goal of 42 MPH.

The boat ran great for  a few minutes and then lost power.   Crap!  Again.  On the suggestion of Cousin XL,  I took it out again and pumped the primer bulb when it started to slow, and holy cow, it worked!   As soon as I pumped up the primer on the fuel line the motor came right back to speed, ran great for a minute and then slowed right down again.   So, I figured this has to be a fuel starvation issue.  The big question is, what is the cause?  I have a few ideas, but I don't want to start tearing it apart and looking in the wrong area.  Air vent is open on the tank. 

Looking for a good, reasonably priced Mercury mechanic in Muskoka since the duel carbs and linkage scare the crap out of me.  I can build boats, but I know my mechanical limitations.

Chris

« Last Edit: August 18, 2013, 02:13:02 PM by jmuskoka »
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george_mason11

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #8 on: August 19, 2013, 03:56:31 AM »
I had an outboard like that a few years ago... turned out to be the fuel pump. It ran perfectly when I pumped the primer bulb and then died once I stopped. I would check the fuel pump.

Does it have a fuel filter?

George
2012 MiniMax- 1981 evinrude 9.9

jmuskoka

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #9 on: August 19, 2013, 01:24:34 PM »
Yup......the carb and filter and fuel pump are the next things that I will tackle.    I'll get this thing figured out yet.   Then, the video will come!

Chris

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jmuskoka

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #10 on: August 28, 2013, 08:55:34 PM »
I finally got the fuel issue sorted out!  It was indeed a fuel pump problem.  I had the pump gaskets replaced on both carbs as well as all of the carb gaskets and needles,  and it works beautifully!  However, (and not that it seems to be an immediate problem) the mechanic who did the work indicated that the insulation on some of the wires underneath the magneto were rotting out.  He said that it was an "old" motor and that it could be expected.   Huh!?!?!    I have a bunch of old green tops and the wiring is fine on those!   The only thing I might suspect is that after the motor has been running the flywheel gets a bit warm.  Could it be the heat causing the insulation to break down?   I'll tear the flywheel off this winter and have a good look.  Electrical problems and wire replacement I can easily deal with myself.

And another thing........What I love and hate about seafleas is working out the small problems when you  get the boat in the water.  I was finally able to take my recently completed Mini Most XL for an extended test run around Kahshe Lake.  The motor worked great, but I kept getting water splashing up from the transom area.  After 10 minutes of driving around, the cockpit was turning into a bath tub!  So.....I shot this video in the hopes of discovering what was causing the problem.  I have a few ideas, but nothing definitive.

Here is a link to the video:  http://www.youtube.com/watch?v=AyJzC335kQU&feature=c4-overview&list=UUMDIEIr9Z4QKQQVsrTGvLqQ

All suggestions and ideas of why this is happening are welcome!

Chris

p.s.  Here is a link to some information about motor height and trim:  http://media.channelblade.com/boat_graphics/templatesites/dts/dealerlibraries/8441/copetipstricks.pdf
« Last Edit: August 29, 2013, 01:47:14 PM by jmuskoka »
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Galactus

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #11 on: August 29, 2013, 02:38:54 PM »
wow what a nice PDF you send to us !! for sure im downlaoding this for future use !! TKX

wildwatson1

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #12 on: August 29, 2013, 09:31:05 PM »
check to see if you have fuel dripping out of the fuel pump vent(bad diaphram)make sure no vaccum leaks feeding fuel pump.if all else fails put t teaspoons of marvel mystery oil in the gas tank.best thing to clean out varnish and cut carbon i have found.

Jbutler

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #13 on: September 02, 2013, 02:42:02 AM »
That looks exactly like what was happening to out boat.   It was worse when the motor was trimmed all the way in.   I'm guessing it has something to do with the angle of the cavitation plate relative to the bottom of the boat.

As a temporary fix I just blocked the water from being able to come up the outside of the transom.  Not very elegant hey but will come up with a better fix over the winter. 

jmuskoka

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Re: Mini Most XL Inaugral Test Run and Prop Selection
« Reply #14 on: September 02, 2013, 03:32:13 PM »
Hi Jim,

I had the boat on Kahshe Lake yesterday to see if I could figure out what was going on.  I shimmed the motor up 1/2" but that did not solve the problem.  My initial thought was the same as yours, the angle of the cavitation plate. 

A very knowledgeable gentleman that I have come to know (Joe Fossey) who was a professional hydro racer told me that if the trailing edge of the hull (where it meets the transom) is not perfectly squared off, then water will have the tendency to travel up the back of the transom.  I had him look at the video and he said that is NOT what is causing the problem. He also suggested the cavitation plate, or perhaps the shock mount on the motor leg catching the water. 


Even with my 1/2" shim, the cavitation plate on the motor is still about 1" below the hull.   I have the  1 1/2" oak keel running the length of the hull that terminates flush with the transom, Andrew thought this might be the issue.  Joe Fossey suggested that the keel would only create turbulence, but also said it should end sooner.  He also indicated that I should shim the motor up at least another inch!

So,  as a short term solution I sealed the motor clamp where it meets the top and back edge of the motor board with some strips of foam weather stripping, but that does not really solve the problem..it's just a band-aid solution.  Joe Fossey put me in touch with another gentleman who is a long time Mercury motor "head honcho"  and I'll see what he says. 

I agree with you about the angle of the motor...the problem is that when I tilt the motor up one notch, the boat porpoises like crazy.......so..........I feel a winter project coming along.   

And Rob (aka) Cousin XL may get the final laugh.   When he was helping me launch the boat yesterday he asked if I cut off the "built-in" trim tab called for in the original plans.  If you recall, the original Mini Most plans call for the hull planking to extend beyond the transom about 3".  In retrospect, that built-in trim tab would have allowed me to tilt the motor at a higher angle with no porpoising...I feel that if I tilt the motor up, (just like you have suggested) then the water splash over the transom will stop.   

This winter, I think I need to fabricate some aluminum trim tabs........this will hopefully allow me to angle up the motor, stop the water splash and prevent porpoising.

I also find it interesting that we are both running Mercury motors with the same problem...maybe it IS Mercury related!?!?!

Chris

p.s.  I spent the better part of the afternoon shooting some video of the boat in the water.  I'm heading up again next Sunday for some more shots.





« Last Edit: September 02, 2013, 03:42:15 PM by jmuskoka »
The Muskoka Seaflea Web Guys - Chris Taylor - Andrew Taylor - Rob Renton