Boat turns up but no push now

[Cypressslipper]

Hey gents, I’ve just gotten a 12ft Hamant w Poly and an angle valve 0360 200. When I first got it I could run dry in my yard. Last night out I had a little more weight in the boat and had to put out my passengers to spin it around. Checked my RPMs on the trailer today and it was 3k WOT. That was on the pace maker box, it doesn’t have a tach yet. Thought I’d add a little more pitch today and got it at 2800k on the trailer at wot. Set it off the trailer and it wouldn’t move itself. Put the prop back to where it was before and it still won’t move. Going into work tonight but I want to check the plugs when I get home. I’m new to these boats and I’m at a loss as to why it won’t push now. It’s a 72Q prop and felt very strong and had great push, now not so much.... thank y’all in advance for anything you can advise and your time.

 

[Blownaway540]

Have you checked both magnetos to be certain they both are firing? @ 1,000 rpm turn one off at a time and see if you only drop about 100 rims per mag off. Get a mechanical tach to be sure of performance. This is your first post in 9 years? Been waiting for a good question!! Hopefully others will chime in who are more knowledgeable than myself, Mark. -EDIT-
Forget about the mags, seeing how you no longer have any!

 

[OneBFC]

Well, "dry" from day to day tends to differ. Sometimes by a great amount. If you didn't mess with the pitch between when it was running fine previously and the rpm was the same before then and now, then you are just experiencing a spot that needs more thrust than you have available and quite possibly you could be down on some thrust due to temperature conditions, etc.

My $ is on the conditions are just stickier if the rpm really is the same at the same pitch with no changes to the boat.

Maybe some AC guys will have better advice. Mine is you need more power or less weight.

Hope you get it sorted!

 

[Cypressslipper]

Yeah, it was definitely a lot dryer today and hotter. I had another buddy say the same exact thing on the way in to work.Thank You Russ and Blown away 540, I’ve wanted an airboat for a long time. Just getting into it though!

 

[Bonefish]

"It’s a 72Q prop and felt very strong and had great push" May be a little too much prop for a 170. A 70" or 68" would probably do a much better job.

 

[Deano]

. . . May be a little too much prop for a 170. A 70" or 68" would probably do a much better job.

Not sure where you are getting 170 from. :dontknow:
72" shouldn't be an issue for a healthy angle valve 360.

 

[Cypressslipper]

Deano, so it says 72q on the hub and only measures 70 tip tip. Anyhow, could I get the rpms and no push from a fuel problem or fouled plugs?

 

[Slidin Gator]

Could be a short hub or a cut down set of blades, either way 70" Q is a real good blade for that engine.

As Deano says, if you didn't change the pitch or anything else significant and are getting the same RPMs, then all good on the engine. As BFC points out, on hotter days, not only is the grass stickier, but air expands, becoming less dense. So the engine and prop do not get as much air. Engine makes less power and the prop starves for air, making less thrust and requiring less power. The two effects roughly cancel out such that at the same RPMs your thrust is down. Less thrust, more friction, never a good combination.

Turn on your sprinklers, I bet she slides real good :cheers:

 

[glades cat]

Put a jar of shine at the far end of your yard and tell your boat it can have sip if it makes it across.
Bet that boat will scoot right along that grass right towards that jar. Feel free to join in the celebration.

 

[Cypressslipper]

Slidin Gator and Glades cat. I appreciate y’all taking the time in replying. Over the years I’ve seen you guys give out lots of good advice. I thank y’all for your time. I knew colder air was better for hp but have never really thought about the thrust part at all! Newbie for sure!

 

[glades cat]

Hey Cypressslipper. Just messing with ya buddy. Yea, there's running dry and then, there's sticky grass. Sometimes, you'll be running on grass with the morning dew, and then it dries up, gets warmer and it's a different running condition. Wait 'till you run up on mud. It'll stick you like glue.
Congrats on your new boat. Post a picture when you can. Slide safe.