Transom Issues

[Mel Taylor]

Re: Transom Issues

Ahh..... OK, but I had this same conversation with my father-in-law (of blessed memory) when he had a spun prop on his boat not long after I spun the prop on my boat. Strangely enough, when he replaced his prop with one of my spare props the problem went away. I don't think you can exert enough force by hand to make the hub slip.

And Now For The Rest Of The Story:

And maybe a little humor. My father-In-Law never did admit that he had a spun prop and when I asked him about it later he changed the subject. The funny part is that he never offered to return the prop I gave him (and it was a gift, not a loan). That prop had a small, but distinctive nick in one of the blades and two or three years later on one of the few occasions when we went to the lake at the same time I noticed that same prop still on his boat as he was launching. Funny thing, human nature. Such things make for good memories too.

 

[foodfisher]

Re: Transom Issues

It's a good idea to carry a spare prop anyway. Pick one up and test when you can dunk the boat.

 

[Mel Taylor]

Re: Transom Issues

Ok, stupid question. Will I be able to just back the boat in the water, leave it strapped on the trailer and try to go forward. I can go out and mark the hub/prop now and stick it in my pond to make this happen. I can unload it into the pond as my banks are very steep. But am able to get the motor in far enough to run it.

No question like that is really a stupid question. I don't really know the answer so you can take this for what it's worth but my guess is that you are going to need to launch the boat and actually run it. Is there any chance that you can simply borrow a prop that is known to be good from someone else, put that prop on your boat and do a test run?

In my case I do virtually all my boating in western lakes where fluctuating water levels with underwater hoodoos and sunken islands are always a danger so I carry a spare prop. The first and only time I spun a hub I happened not to have a spare with me. Plus, I didn't realize what the problem was until someone else in my party told me when I got back to shore.

 

[Mel Taylor]

Re: Transom Issues

It's a good idea to carry a spare prop anyway. Pick one up and test when you can dunk the boat.

That would be my suggestion too. The only reason I didn't mention it was that after not having had a tachometer on my boat for a long time, I installed one last year and found that RPM was too low at WOT. I ended up buying and trying couple of props before I hit the right range.

I thought he might be better off making sure it was really a spun prop before he went any farther.

 

[ezmobee]

Re: Transom Issues

I've had two spun props and neither were really bad. One you kinda had to have a full load for it to do it, and the other you had to really nail the throttle. If yours is like these, I don't see how you're going to replicate the issue by attempting to spin it by hand or by running the boat on the trailer. If you don't currently have a second prop, as mentioned, it's a good ideal to have a spare so I'd buy one anyway and put that one on and see where you're at.

 

[roscoe]

Re: Transom Issues

This is a straight edge off the bottom of the hull as requested. The distance between the cav plate and the straight edge is roughly 2.5 inches.

Ruler is resting on the anti ventilation plate, and touching the bottom of the hull, can't get any more even than that.

 

[HNTDUKS]

Re: Transom Issues

Prop hub is not spun. Just put it in the water. Problem seems internal. Bow comes up, engine starts to wind up. Then all forward movement stops and engine revs. Almost as if someone put it in neutral.

Left the boat and motor at the marina where I bought the motor 2 weeks ago.

 

[foodfisher]

Re: Transom Issues

Are you forgetting to mention a thud or clunk when it looses forward momentum?

 

[little.boat]

Re: Transom Issues

My boat was doing the same thing just last week, mine was a spun hub though. New prop on it today and it ran like a champ.

 

[Jedo_03]

Re: Transom Issues

Coincidence...
I have just logged in to ask this same question..!!!
I'm close to having an answer - but confused as to which is the Cavitation Plate and which is the Ventilation Plate...
Here's a pic of my OB...
Which is which please..??
And which plate should be level with the bottom of the hull..??

 

[saumon]

Re: Transom Issues

The name is "anti-ventilation" plate (but sometines called incorrectly "anti-cavitation") and it is the lowest one (right above the prop), its purpose is to reduce the air being sucked by the prop.

The small one above is a "deflection plate" and the purpose of this plate is to prevent water from travelling up the exhaust housing due to hydrodynamic pressure (rooster tail).

Well written article: http://www.louisianasportsman.com/printer_friendly.php?id=1795

 

[Jedo_03]

Re: Transom Issues

Thank you, Saumon...

 

[HNTDUKS]

Re: Transom Issues

Got the boat back today. Nothing internal was causing the issue. The issue was cavitation. The marina added a mini jack plate at transom level, which in turn got the motor far enough away from the "wash" of the hull and cured the problem. Boat runs like a scalded dog now.

They said that the transom height of 16 inches was just enough to throw that motor off where it should be. Cost me nothing but a drive to and from the lake.

 

[foodfisher]

Re: Transom Issues

Got the boat back today. Nothing internal was causing the issue. The issue was

cavitation.

The marina

added a mini jack plate at transom level

, which in turn got the motor far enough away from the "wash" of the hull and cured the problem. Boat runs like a scalded dog now.

They said that the transom height of 16 inches was just enough to throw that motor off where it should be.

Cost me nothing

but a drive to and from the lake.

Need help with these.

 

[MH Hawker]

Re: Transom Issues

Glad you got it sorted out.