23HP : 4.5mph idle, 6mph full throttle! What's wrong?

[AIRMAN]

Hi all. I took my new airboat out yesterday. It has a 23hp Vanguard on a 13'x5.5' hull. Anyhow, the thing is going 4.5mph at idle and 6mph at full throttle. My ears are still ringing... even with earplugs and muffs this thing was unbearably loud. As you increase the throttle, it picks up speed for about the first 20% of the carb opening, up to 5.5mph, and then with more throttle it just gets louder and louder. It has a 42" Arrow wood prop of unknown pitch. I think maybe I need a new prop. What do you think would be best? I can't fit more than a 42" in my shroud. I am new to airboats and am not real familiar with how it all works. I would really appreciate any advice. Thanks so much!

[Papee]

I answered in you other post also,


Welcome to the forum. A 42" prop sounds right for that setup. You may want to experiment with weight distribution, moving your battery, and gas tank forward. I did one with the same setup you have it it rode with the nose very high in the air until we moved some weight and adjusted the engine shims. It's not going to be a speed demon because the bottom is not wide enough to displace the weight but it will make a nice all round boat.

[David]

Could you get us a picture of it and post it here

[AIRMAN]

Hi David. I will try to get some pictures next time I am out. I have been so excited I keep forgetting to take any. It is a real neat little boat. It has great seats and I sat in it 4 hours straight on Friday with no trouble. People take pictures of it all the time as I cruise by. I am actually very pleased with it but I still hope to get the exhaust noise down somehow. Thanks for the info, fellows. Glen