A couple of Motor questions

[TnT]

I finally put the "Project Boat" in the water on Friday. The good news is that it didn't sink ..The bad news is that the prop had spun the hub in it. The motor did run excellent tho....So I left it in the water and gave my trailer a makeover during the weekend. I went back Monday to get the boat and put a different prop on it and she ran out great. But after about 10 minutes or so the bubble "collapsed" and stopped feeding gas to the motor. I had to disconnect the hose from the bubble to release the pressure, reconnect the hose to the bubble and it started pumoing again like it was suppose to. The vent hose does not have any obstructions in it. I know that the fill tube is OK(I had to fix that last week)...So what else could be causing the bubble to collapse?

My 2nd question is the pitch on a prop....I took a 23 pitch off and put a 17 pitch on it. I know one pitch will cause the boat to have less hole shot and one will give it more speed at top end...Which does what.??..I am not too concerned about top end speed, I just want to have less hole shot.

Tim

[Shine Runner]

Sage can probably help you on the fuel line stuff. Was it a new hose and bulb? As for the pitch prop, I believe higher pitch = more top end and less of a jump on take off. Tricky part is getting the correct pitch prop to give a good hole shot and the correct RPMs for cruising for that motor. Should be able to find online the correct pitch for that motor. Of course, hull weight and other factors can change the recommended pitch for each boat. Just what I think, but have been wrong before.

[sorrydog]

TNT, Go the cheapest route first, try another bulb and hose. They do come bad since most of them are made in China now a days.Next and if that don;t work, get a 5 gallon bucket and just run a line into and it and let it run. If it shuts down, you got a blockage somewhere on the engine. Had a merc that did that. The fuels lines on the motoer dry-rotted in the inside and was clogging-up the carbs. Worst case---fuel pump!

Good Luck!

[gtojoe]

Shine is correct about the prop. You can change the pitch but it will change the rpm that the motor will run at. The best thing to do is find what the motor came with. what the recomended rpm range is and stay within a few numbers of pitch from the original. The average rpm change is about 200 rpm per pitch number. Take it out and see what your rpm is at full throttle. The manufacturers web site should have a list of all the recommended props and rpm ranges for your motor. There is also a company in Monroe GA called propco that makes and sells props at very good prices.
As for the fuel. The check valve in the bulb could be sticking, the hose could be bad on the inside or your pick up could have some kind of restriction in it. Hope this helps.

[crappiechappy]

I'm with Sorrydog. I'd replace the whole fuel line, especially if the motor has been sitting up for a while. Even if the hose looks good on the outside, it could be eating away from the inside especially if ethanol is involved.

[EARL KITCHENS]

I had the same fuel issue on a Bass Boat before and it was the anti drain back valve in the top of the fuel tank. It was closing in both directions and starving the engine for fuel. It would idle great but would not let the fuel flow on throttle.

[thespiderman]

I agree with Earl. Check the valve on top of the tank first (that is the cheapest thing to do first), then your fuel line, then start looking at the motor. As far as the prop question, I just went thru the same thing with my boat. I'll try to make it short. I have a 17' aluminum Triton and a 70 hp Yamaha. I started with a SS 13.25 x 15 prop from Propco. The first time out it turned 4300rpm's and top end speed was 29-30 mph. I took the prop back to Propco and he trimed it down to a 12.75 x 15. The motor went to 4400rpm's and a top end speed of a solid 30 mph, not much difference. A friend recomended a dol-fin (alot of people don't agree with them). I put the dol-fin on and instantly I went to 5100rpm's. Still not satisfied, I bought a Solas aluminum 13.5 x 15 and put it on. I was now turning 5400rpm's and running 33-34mph. I then ordered a Solas SS 13.5 x 15. I am now at 5600rpms and top end speed of 35mph with a full tank of gas and 2 people in the boat. When you look for a prop, don't just look at pitch, also look at diameter. It worked for me.

[TnT]

I should have added this in my original post. I just put a new line and bulb on it last week and checked the pick up line. I also replaced all the fuel lines under the cowling. The tank is an on board 21 gallon tank with a new vent hose and vent that mounts on the side of the boat.

[crappiechappy]

If you don't locate the issue, there is a guy in Dublin that I highly recommend. Pete Cliatt and his son do all of my boat work. Let me know if you need his contact info.

[papasage]

choose a prop fror the boat and motor and use of it but din`t prop where where rpm`s will be over specks . usealey 5000 or 5500. for my pontoon it has 4 blade 10 in pitch run it 13 mph . with a 3 blade ss 16 pitch blade ran it .reeal slow. like walking speed . as far as the gass line sounds like it is not making a good conection . had one that did that and the quick conection was bad .

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