This look right? Cav/vent prob.

[HeavyObject]

Just trying to sort out some issues. This is the first boat over 14' and 10hp I have owned. Boat info is in sig.

Runs ok set in this hole, but will cav/vent in semi hard turns. Cavs/vents easy in the two upper holes going strait in rough water. Looses 3mph in the lower holes as the bow is down.

I assume I have the black bar on the cav plate? The center rib is around 1" below the plate

Side view.

Fuzzy shot from further back.

Needs a new prop but I need to get the tach working first. Current prop is a 13 1/4 x 17p. I can't drop the engine any lower without notching the transom, so does it look like it's low enough? Transom height is around 21 inches but I can't get an accurate measurement with the engine mounted. Comments or suggestions?

 

[WillyBWright]

Re: This look right? Cav/vent prob.

Sounds like you want the speed of higher mounting without blow-out. Solve that and you can be a millionaire. It's an either/or situation.

 

[steelespike]

Re: This look right? Cav/vent prob.

I think if you get the prop repaired you may solve your problem. adding some cup may help but until you know your rpm you can't tell if the cup will drop you below your proper rpm range.Prop needs repair as it could cause seal and/or bearing failure.When you get the prop done let us know how it does.

 

[HeavyObject]

Re: This look right? Cav/vent prob.

That prop has been repaired by someone before, I can see the new alloy that was added to the tip of the blades. I did hammer a bent tip back into place plus there is that little chunck still missing. I plan on new prop after I figure out the running rpms, but wanted to make sure nothing else was wrong. I kind of feel the engine should be down another inch or two but I can't set it any lower...

 

[Dhadley]

Re: This look right? Cav/vent prob.

Once you get a decent prop you'll find the motor is too low. Fix the tach, replace the prop and then start testing and raising the motor.

 

[HeavyObject]

Re: This look right? Cav/vent prob.

Just noticed one of the blades on that prop is longer then the other two by about 1/2". Nice repair job!!! Guess I need to buy an 13 1/4 x 17p OEM replacement before worrying about a Stainless Steel upgrade....

 

[Dhadley]

Re: This look right? Cav/vent prob.

If it were me I'd go to stainless.

 

[steelespike]

Re: This look right? Cav/vent prob.

Don't be jumping to stainless until you establish your rpm with your repaired prop.Repair is generally much less than new.If you still want to up grade to a stainless keep the repaired one for a spare.No doubt the stainless will perform but keep in mind they are a little harder on the gearcase especially if you hit something.The aluminum will soak up the impact.
By the way if you lower it an inch you could lose 2 to 3 mph and some hole shot.

 

[HeavyObject]

Re: This look right? Cav/vent prob.

I am debating on a stainless of similar specs to the one that's on it only if I can't find a good used oem prop on the local dealers prop wall or locally. I tend to avoid ebay but there are a couple oem props on there right now. For the most part the rpms seemed fine during the 25 or so miles I put on the boat setup like it's in the pics. Does anyone have any spec recommendations for a stainless replacement? It's a 13.25x17 now so am I correct in thinking a 13.25x15 stainless would run similar rpms just be more efficient? Thanks

 

[steelespike]

Re: This look right? Cav/vent prob.

Yes generally you drop in pitch going to stainless but::
"Rpm seemed fine" is not a great way to figure if you are within rpm specs.
If you are under or over you can damage the motor.Not to mention poor preformance and mileage.If you are buying a prop locally I would think they would have a shop tach you could check your rpm with.You probably have the right prop allready isn't there anyone to repair it in your area.Then you could check your rpm and know exactly where you are at.
I can't imagine forking out money for a stainless prop and not even knowing for sure what the right one is.
You need a good solid baseline setup to tell where you are at.You need to work your setup with a good prop you may even be able to raise it a little before making the stainless decision.

 

[HeavyObject]

Re: This look right? Cav/vent prob.

What's the general cost of a prop repair? Getting a baseline wiith this or another 13.25x17 prop is my 1st choice then a ss prop and then a nice 130hp engine then a......

 

[steelespike]

Re: This look right? Cav/vent prob.

I'm guessing on prop repair,haven't had one done in years.I believe most shops charge a flat rate based on prop size.A 50hp used to be about $25
I would guess at least $40 now.Find a shop and give em a call.If you go through a marina they probably get a little off the top for their time.Maybe someone here has had one done recently.
Now that this has gotten into a prop discussion
it needs to be in the prop forum once you have your repaired prop and info.
They will need details on the boat,type of use,typical load,type of motor and hp.present rpm and speed preferably with a gps and known accurate tach.Without this info its like taking your car to the shop and saying there's something wrong with my car let me know when its done.Again if your buying locally they may let you use a shop tach and may let you try props based on the info supplied from the forum.
The guys on the prop forum are very good when they have the correct info.

 

[HeavyObject]

Re: This look right? Cav/vent prob.

They wanted $50+ to repair my prop and $70 for one they had on hand that was done. Didn't want to make another trip so I bought the one they had. Also got a used tach that was pulled for someones upgrade to a new engine. I'll be out of town for the week so I just need to find time to mess with the boat now.... Thanks for the help.

 

[steelespike]

Re: This look right? Cav/vent prob.

OK ,good luck let us know how things turn out.

 

[HeavyObject]

Re: This look right? Cav/vent prob.

Getting closer to boating season again so...

The new prop didn't cure any of the cav/vent issues I was having, performed exactly the same. Still don't know what the cure is.....

 

[F_R]

Re: This look right? Cav/vent prob.

I would say that you have done the best that you can. You seem to say it vents on hard turns but is OK otherwise. If you want to go further, there is power trim......

 

[JCF350]

Re: This look right? Cav/vent prob.

I would say that you have done the best that you can. You seem to say it vents on hard turns but is OK otherwise. If you want to go further, there is power trim......

My first thought upon description of the problem. Didn't notice "no power trim in the pics":redface:

 

[MikDee]

Re: This look right? Cav/vent prob.

Just found this thread,,, Just so you know when you don't have power trim, the basic (standard) trim setting is to make to the Cav. plate as close to paralell (in a straight line) with the bottom as possible, using a straightedge. Otherwise, the bow will plow, and raise the prop outta the water some, causing ventilation. Next, Your up, & down height isn't bad, but the higher you can go with the Cav. plate (generally flush with the bottom or a bit higher) will give you more speed, just keep the Cav. plate level,,, in the future, you might try angling the motor (Cav plate) up one hole at a time to see if it performs any better, angling the motor up some is the more desired effect, rather then angling it down.

 

[HeavyObject]

Re: This look right? Cav/vent prob.

This could be the cure I am looking for. PT&T is something I would like to add and I think the 6" setback would help as well. Tough to spend that kind of money on a boat that I paid $1400 for.

Been wondering if the hull is causing some of the issues too...


Edit....

I reread what I had originally posted and I guess I could clear this up. I have not changed the vertical height of how the engine is bolted to the hull. Just the pin that sets the level of the cav plate. The best compromise is the way it's set in the pic. The bow plows in the lower setting and vents easy in the three upper holes.

 

[F_R]

Re: This look right? Cav/vent prob.

You said: Been wondering if the hull is causing some of the issues too...

Absolutely. When you throw it into a hard turn, you lose speed, the boat is going sideways to a certain amount, the boat settles deeper into the water, the boat is digging a hole in the water, and the water is no longer approaching the motor from the same direction, etc. All this combines to cause your ventilation problem. That is why I suggested you have reached the best you are going to get with what you have. That is, optimum performance under normal conditions. Sure, you can drop the motor down and maybe reduce your ventilation, but at the cost of reduced performance on the straightaway. I doubt you are willing to sacrifice that.

A power trim will allow you to tweak trim settings underway if you like to play with such things.