Finished mud motor today 13 hp. Ran great on shore. Once prop hit water the belt broke with in 5 feet. I am using timing pulley L series 3/8 pitch 1'' wide. Do I need a belt tension on it. I have the belt as tight as a good get it. Any help would be grateful Thanks

Side shot of that rig please, looks to me like your belt housing Is too long.

Also, you do need some tension on the belt, did it shred the belt or just pop?

Not sure why your belt broke, maybe bad off the shelf ? Also, L pitch pulleys are for light duty but I can't see why your belt would break. H pitch pulleys are 1/2 inch pitch and for heavier duty hp ratings. In addition, I think the belts are stronger for h pitch and can be purchased with a kevlar backing. Just a thought. Did the belt show signs of breaking or shredding? Hope you get it straightened out.

The shaft is 4.25'' centered from the bottom of the boat.
The belt did not shred clean cut.

Either your belt was the wrong type/material, or you were over tensioned. What type of belt were you using? If it were too lose, you would have slipped the belt and tore cogs off of it. This is one of the reasons that I only use Gates belts. You can use their software to design the entire system and you will know exactly the rated horsepower. I typically use a 3X service/safety factor because of the shock loads these drives will see.

Is the center of the shaft 4.25" below the bottom of the boat? It should be that or more ABOVE the bottom surface of the boat. You are going to catch a lot of resistance in the water and create a snag point for everything you drive through.

Housing is 2'' from bottom of boat an 2.25'' from there is my shaft. I have tired fining that gates software but no luck on the down load.

I am using L series not sure if I can get a stronger belt for it.

http://www.gates.com/dfproweb/index.cfm

You are looking for a Powergrip or PolyChain belt

The current belt and pulleys you are using are not good in this application with fairly high rpm and shock loads. I can't find any info on the rated Hp for that belt. Were you able to find anything when you were putting it together? Even with a higher strength belt, I would still be a bit afraid of using a square tooth/cog system. What ratio and prop are you running?

I would also shorten your belt housing. What length shaft are you using? You should be able to raise the center line of your output shaft up to 6-8" above the bottom of the boat and also keep the bottom of the housing 4-5" above the bottom.

Ok I need get a different belt system then. Think a chain would work or go with the H series pulleys. So if the bottom of the pulley housing is 4-5 inches from the bottom of the boat then the center of my shaft would be 6-7'' from bottom. Shaft length 36'' 4'' in the housing an 4'' for the prop. 19 on top an 24 on bottom which would give around 3000 rpms at prop running motor at 4000 rpms Thanks for the help

Few more pictures

Raise your belt housing, cut that shit off and make a real skeg!

The short rake on that one will tangle in grass easier and make hits a hell of alot harder than a skeg that ran the length of the shaft.

Thanks for the info I will change it.

Ahh those are better pics. The shaft is long enough that moving its centerline up will not impact you as much as having the belt housing down where is can pick up weeds and catch the flow of water. As for the belt, you could try one of the heavier duty belts with the same 3/8" pitch, but I would personally spend the money on a Gates belt that is a designed solution that will have a hp rating.

I could not download the gates program so I left an email. Thanks for the help

You should be able to run it online. There are 2 options online and downloaded

I will see what I have from my first 13 hp build. May give you a starting point

Got the software up. Not sure what to punch in.

Click on Polychain and Powergrip belts
Your Hp
Driver is your motor shaft diameter
Driven is you output (prop) shaft diameter
Add any diameter or width constraints
Depending on what size prop you are trying to turn, you will have to decide your ratio. This will be speed down
Go to the worst case on all of the loading questions, this will drive the safety factor.
Your center to center distance from motor shaft to output shaft

When you have the list of drive options, review them for what fits you envelope the best.

Sorry, If I missed something trying to do this from memory.

On my 13 hp build, I used a 8mm pitch, 21 mm wide belt
top (driver) pulley was 28 tooth and bottom (driven) was a 42 tooth.

Thanks Mag. Does a 1.32 ratio sound good. Program keeps saying wrong speed. But I did get help through emails from the sale manager.

Does a 210 Lbs pull sound right. Did you have a tension system on your build. Got the the design software working. Looks like 8m belt Thanks again for your help.

What size prop are you trying to turn? I typically use a 1.5:1 reduction as a starting point. With your 13 hp and 1.5 reduction you should be able to turn a 10x8 prop in a lightly loaded boat. I always build in a tensioning system if possible. not an idler pulley.

10x8 prop is what I have. I was going to use a idler. What else can be used.

Where did you get your grip throtle.

Came off a jet ski I parted out.

Cool Thanks

An idler can be used, but it adds another potential break point. I typically have a slotted attachment between my motor mount and the belt housing and then a tensioning bolt to drive the driver and driven centers away from each other to tension.

OK That is how mine is set up.

Got price on belt an pulley. Belt 56.00 Pulley an bushing 80.00 the other pulley an bushing 83.00 That going with a 21 mm Wow Thinking chain route.