Won't plane, Prop spins out on stratos 201 pro

[Dan_the_fisher]

On May 17, 2016 at 3:12 PM, Glenn said:

If you've done the following:

• Tried different, new props (to rule out spun hubs)
• Tried different engine heights
• Verified trim gauge is working and accurate
• Verified trim is working the full range
• Verified there is no water in the power trim hydraulics (this would cause the motor to lose trim functionality).

Then take it to a mechanic to

• Check the power trim unit. It may need replacing.
• Tear apart the lower unit.  Something wasn't done right during the rebuild.

I think it's the latter of the two, the lower unit is brand new before we got the boat and we are thinking it is the problem now. 

[Dan_the_fisher]

Ok checked the gear ratio in the lower unit by putting it in gear and spinning the prop by hand, and I got roughly 1 8/10 of a turn on the flywheel for one complete turn of the prop.

[Ski213]

It sounds like the ratio is right. So with the 3 blade you said it runs fine. Meaning once on plane it's all good but holeshot is still no good? 

[Dan_the_fisher]

1 hour ago, Ski213 said:

It sounds like the ratio is right. So with the 3 blade you said it runs fine. Meaning once on plane it's all good but holeshot is still no good? 

It seems to do fine once it planes out

[Bob C]

Can you post a picture of the prop and lower unit?

 

[Dan_the_fisher]

Yes when I get home 

[Dan_the_fisher]

[WRB]

What is with the zinc plate below the cavitation plate?

Tom

[riverbasser]

I don't want to add the all the questions but I read you adjusted the engine height to different positions but you need to do as Tom said and set the cavitation plate level with the bottom of boat and leave it there. Lower pitch props bring boat on plane faster and hold it there. So you may be over-propped. 

When you say the prop is spinning out you are sucking air and need to trim down. Do you ever experience and porpoising? Also what about water spray? What does the water look like coming from back of boat? 

[Further North]

My knowledge of props is limited to the fiddling around I've done with mine...but in the pictures, it looks like the prop has a smaller diameter than the part of the lower unit it butts up against...could that have something to do with the problem?

Every prop I've had has had the same diameter there.

[Tim Kelly]

That's a good spot. If the exhaust gasses are spilling out around the prop it would cause the issues you're having trying to come out of the hole, but be fine once you were up and running. Much like having too much venting on a vented prop.

[Dan_the_fisher]

11 hours ago, WRB said:

What is with the zinc plate below the cavitation plate?

Tom

I assumed that was the alignment to make it run true, I honestly don't know what all they do 

7 hours ago, Tim Kelly said:

That's a good spot. If the exhaust gasses are spilling out around the prop it would cause the issues you're having trying to come out of the hole, but be fine once you were up and running. Much like having too much venting on a vented prop.

So the prop could be incorrectly mated to the lower unit? I have another boat and haven't been running this one, I'm trying to get it fixed now to sell. So I haven't been testing much on it lately 

[Further North]

7 hours ago, Tim Kelly said:

That's a good spot. If the exhaust gasses are spilling out around the prop it would cause the issues you're having trying to come out of the hole, but be fine once you were up and running. Much like having too much venting on a vented prop.

...and the prop is vented as well...

10 minutes ago, Dan_the_fisher said:

So the prop could be incorrectly mated to the lower unit? I have another boat and haven't been running this one, I'm trying to get it fixed now to sell. So I haven't been testing much on it lately 

Sure sounds like it could be part of the problem.

[WRB]

Could be the torque tab, in the photo it looked it was attached to the side of the hub area, not behind the prop on the cavitation plate. The zincs are usually above the cavitation plate and they are shown in 1 photo, zinc help to prevent castrohphic corrosion from salt water.

The prop looks like a normal OMC SST with vents, look big are the holes threaded for plugs? The only thing I can think of is the prop shaft bearings allow prop shaft wobble, that will cause problems. You could have a hook on the planing pad, from the trailer pads, but that doesn't cause cavitation issues. If the hull has glassed over wood on the transum, wood can dry rot severely weakening the engine mount.

Beyond me!

Tom

 

[gulfcaptain]

Just looking at your pics, that zinc tab that hangs down I'd replace with a flat zinc.  It may not make a difference but with the prop cutting through the water that may make a cavitation hole on the back side of the tab/side on the down spin from the prop.  It might be causing an issue where it sucks air slightly which could lead to that issue you're having.  It's just a thought but it's an easy thing to rule out by just taking it off and seeing what happens. 

[Tim Kelly]

If the prop mounting looks ok, to those with a similar set up, then maybe the ports in the prop need plugging or reducing. Presumably you can get plugs like you would for Merc props?

[Kevin22]

19 hours ago, WRB said:

What is with the zinc plate below the cavitation plate?

Tom

where? The trim tab you mean (behind prop)? Looks homemade out of a chunk of steel.. Probably not the cause of the problems but something i would replace. 

 

[Further North]

The first thing I'd do is get a prop on the motor that is the same size as the cone housing...

[Ski213]

I'm not saying the prop isn't your issue but assuming it's the correct prop for the setup it is my understanding that it ok for it to be smaller than the OD of the lu housing. There is a plastic ring that I've heard called a weed ring or ventilation ring between the prop and housing. Yours looks to be present. My 225 is the same setup different prop and I have no issues. My prop does have a very defined flare at the rear.  I can't tell if yours does or not. Looks like yours may have a taper to it. North brings up a good point though and I would definitely make sure that the prop is correct for your application.

[WRB]

Re read this entire thread and one statement jumps out "45 mph before trimming up, then the boat flies". Bass boat get on plane at 25 mph, then start to trim the engine to increase speed. I am thinking your problem may be your driving skills, heavy boat and 3 blade prop.

Borrow a 4 blade prop that is right for your rig and test drive it.

Tom

PS, the side view of the lower unit looks normal, odd torque tab. 

[Bob C]

On ‎5‎/‎20‎/‎2016 at 7:57 PM, Dan_the_fisher said:

The prop hub is too small. Get one the same size as the lower unit housing and you'll cure your problem. The exhaust has to go through the prop, not around the outside.   

[Dan_the_fisher]

1 hour ago, Bob C said:

 

I'll look at it more when I get home, it's been to a mechanic a couple times I thought he woulda noticed if that was the problem. And also if it is how would it let it run fine on plane? 

[Bob C]

51 minutes ago, Dan_the_fisher said:

I'll look at it more when I get home, it's been to a mechanic a couple times I thought he woulda noticed if that was the problem. And also if it is how would it let it run fine on plane? 

I went through the same problem with Javelin I bought a few yrs ago. If I eased into it until I got on plane it would go about 40 mph. If I hit the throttle from a start it would go nose high and wouldn't recover. I changed the prop for one with the correct size hub and it would go on plane instantly and topped out at 55. The exhaust blowing on the outside of the prop hub and onto the blades caused a major cavitation.

[Fishing Rhino]

You can "help" a boat get on plane by steering it left to right a bit.  How much is a bit?  Something that can only be determined by trial and error.

The "V" in the bottom of the hull provides lift when the hull is forced sideways by steering input.  The left/right/left/right steering is like rocking a car when it's stuck in the snow.

I agree with those who say the diameter of the prop's hub is too small.

[S Hovanec]

6 hours ago, Bob C said:

The prop hub is too small. Get one the same size as the lower unit housing and you'll cure your problem. The exhaust has to go through the prop, not around the outside.   

This was my problem when I bought my boat.  The dealer set it up with a prop for a 130hp which has a small gear case than the 135hp.  The exhaust was blowing out in front of the blades.

 

Almost no gap with the proper prop.