Provee Prop and Pipe help needed.

[David Krienke]

I have a provee I am working with that has a chinese 29.5cc and the zippkits drop down header with a ebay pipe. I am noticing that I am not seeing the rpm that I am compared to my 26cc engine. I have the pipe as short as i can maybe can go another 1/2 inch if I put the clamp in the mandrel bend part of the header. I have tried a few props and they all go about the same speed it seems. Also I did try a little leaner but not much difference and the plug on this engine is still pretty black and unsure why even if I lean it it was still black. maybe I need to really go in on the needle. i have 7016/3, 6714/6, x670/2 props I have tried and 43 mph was about the best we could get out of it. It seemed with all these props it never seemed to load it down. If this engine just runs lower rpm is loading it more needed or maybe exhaust port raised?. What is a good prop recommendation for this boat and engine combination?. Here is a video from today sorry for video quality mid way though there is a couple good pulls .
Edit:
I just Removed that aluminum snorkel off the carb . I was at 1 and 3/4 turns on high needle I had heard that sometimes those snorkels are not a good idea . I will try it without,. also I pushed the pipe as short as I can and its at 12 inches best I can measure with this header. It is hard to get the exact measurement. I had to put aluminum pop can to cover the slots on the muffler and some silicone tape. I noticed it was leaking today because the hole in the hull has black on it as it was. I will be neat to hear if anyone else has had good luck with this header.
Also do these turn fins and trim tabs cause a bunch of drag Should I sharpen these fins more?. and I have the trim tabs about 2 index cards thick above the bottom should they be higher still ? It does really ride flat and nice but these might be drag too.

 

[rhomodel]

Nice build!
A few things I would try to elminate thinks:
If you have 26 cc engine put that in and see what rpm and speed you get. If it is about the same you know it is not the engine, but something hull-prop-rudder-trimtab related. If suddenly you go much faster you know it is the engine.
What carby do you have: chinese one or a 257 / 1048? I would just lean it in if your plug stays so black: about 1 on the H and 2 on the L for a 257.
Measure up your timings: exhaust timing should be in the 175 to 180 degree range..

On the carby: What you call snorkel is called velocity stack. I don't think that makes a lot of difference.. Good luck!

 

[David Krienke]

Nice build!
A few things I would try to elminate thinks:
If you have 26 cc engine put that in and see what rpm and speed you get. If it is about the same you know it is not the engine, but something hull-prop-rudder-trimtab related. If suddenly you go much faster you know it is the engine.
What carby do you have: chinese one or a 257 / 1048? I would just lean it in if your plug stays so black: about 1 on the H and 2 on the L for a 257.
Measure up your timings: exhaust timing should be in the 175 to 180 degree range..

On the carby: What you call snorkel is called velocity stack. I don't think that makes a lot of difference.. Good luck!

Thanks for the tips. Its a Chinese carburetor. The 26cc carb is the same carb and they both work perfect as far as throttling and starting . I just may need to lean it more as you say .I appreciate it.
Thanks Dave

 

[Joe Petro]

That pipe looks way, way too short for a dry pipe. 7016/3 is an excellent prop. The carb looks like a copy of the 644. We ran them at 1-1/4 on both needles initially.
Boat looks excellent! Good job!

Joe

 

[David Krienke]

That pipe looks way, way too short for a dry pipe. 7016/3 is an excellent prop. The carb looks like a copy of the 644. We ran them at 1-1/4 on both needles initially.
Boat looks excellent! Good job!

Joe

Hi Joe thanks for replying. I went and put it back to 13 inches again. I also took a pop can and cut a 1.5 inch strip about 6 inches long and was able to make a sleeve around header and inside the pipe flange. this one leaked real bad out the slits now its air tight. I will try it again at the longer length. As well I will try the 7016/3 again and lean it down some and see if speed improves. Also the bushing in my strut slid all the way out to the drive dog. Should I try Loctite it into the strut? or does it matter ?

 

[Roxyflash]

I would ditch the pipe setup and buy a zip kits pipe my scratch built boat with a older bh Hansen hornet motor with zipkits pipe and a Prather 275 first run was over 50 mph I used a Chinese. Carb off eBay

 

[David Krienke]

I would ditch the pipe setup and buy a zip kits pipe my scratch built boat with a older bh Hansen hornet motor with zipkits pipe and a Prather 275 first run was over 50 mph I used a Chinese. Carb off eBay

Yeah your probably right. My brother had just bought this pipe and gave it to me . It does pull any prop I throw at it and wont load it down and it has instant acceleration and power. but just signs off and there is just no more rpm. I wish I had a bigger prop to atleast be able to get it to fall on its face . I just wonder if this engines exhaust port is low. I just dont want to take it out to check it yet. having too much fun running it . . I will have to order a pipe though soon if I can get a handle on this one. I wonder if that massive exhaust leak at the slits now sealed up will change the way it runs too.

 

[Roxyflash]

The carb was a wt16 b that I switched the carb shaft and top cover to get rid of external pulse fitting I believe I’m at like 1 1/2 on each needle there like 10 to 12 dollars

 

[David Krienke]

The carb was a wt16 b that I switched the carb shaft and top cover to get rid of external pulse fitting I believe I’m at like 1 1/2 on each needle there like 10 to 12 dollars

I really appreciate that. That's a great deal says its for a 28cc sthil chainsaw and others. I bet it works great.
I ordered that carb .10 bucks even get some freebies like some fuel line filter and plug . thanks for the tip.
Also
I just bought a tachometer for them a sec ago. that will be nice to see as well.
https://www.ebay.com/itm/234275221535

 

[Joe Petro]

Let the bushing float. No problem with that.