What kind of outdrive...?

[rauch0812]

I need to purchase a cavitation plate and new prop for our boat and I don't have a clue what kind of outdrive we have... how do I figure this out?

 

[Tail_Gunner]

Re: What kind of outdrive...?

That would be a merc...Now why a cav plate.....looks good from here..looking for clues.......Umm im hopeless i guess

 

[steelespike]

Re: What kind of outdrive...?

You'll do better in the I/O section.Get us as much info as possible.Gear ratio
may be on the outdrive.Info off motor 8,6 or 4 cylinder 2.5,3.0,4.3 etc.
Size of prop on the barrel or under the prop nut.More detailed pics may help us identify the outdrive.I have a feeling the antivent plate will be an expensive proposition.Whats wrong with it?

 

[rauch0812]

Re: What kind of outdrive...?

Cavitation Plate: we're having trouble with the boat pulling to the right and we were told to adjust the cavitation plate. This weekend we looked at it and that silver disk is missing. We're told it should have a fin on it...? (new posting correcting this below... disk is NOT missing)

Propeller: The boat is a Larson 206Lxi 20' Bowrider. It has a 5.0L Mercruiser engine and the horsepower is 210 or 220.. I'll drive out to the marina tonight where it's stored and get pictures of the outdrive.

How do I figure out ... "Size of prop on the barrel or under the prop nut" ?

 

[Tail_Gunner]

Re: What kind of outdrive...?

Cavitation Plate: we're having trouble with the boat pulling to the right and we were told to adjust the cavitation plate. This weekend we looked at it and that silver disk is missing. We're told it should have a fin on it...?

Propeller: The boat is a Larson 206Lxi 20' Bowrider. It has a 5.0L Mercruiser engine and the horsepower is 210 or 220.. I'll drive out to the marina tonight where it's stored and get pictures of the outdrive.

How do I figure out ... "Size of prop on the barrel or under the prop nut" ?

No need the part you are refering to is called a trim tab or trim anode..

http://www.iboats.com/Mercury-Marin...65146874--**********.343121863--view_id.39250

But you should post the pitch of the prop and as spike has said it is located either on the barrel or under the prop nut...along with your engine rpm at WOT..speed would be nice...Its really needed to make a good pick

 

[rauch0812]

Re: What kind of outdrive...?

Cavitation Plate: Ok - my first post was wrong... that silver plate IS there and nothing is missing... the advice was to add what I was calling the "fin". Now I know it's called a trim tab or trim anode. Thanks for the link - that's the cheapest I've ever seen anything for a boat! LOL. How do I tell if that one will clear the prop? I can't find any specs on the website about it.

Prop: I'll look for those numbers when I take the pics... I'll post back.

Thank you for your help!

 

[Tail_Gunner]

Re: What kind of outdrive...?

THats a high perf tab...Its set back farther than std tabs...It will work now and in the future

 

[rauch0812]

Re: What kind of outdrive...? What kind of prop?

Re: What kind of outdrive...? What kind of prop?

What kind of outdrive?

Should I be able to turn this plate about 1/4" back and forth with my fingers?

Can not find ANY writing on the prop or the shaft (inside or out). The max WOT on the engine says 4400-4800 and the HP is 220. How do I pick a new prop?

(I tried to make the pictures smaller but I'm not doing something right...)

 

[Tail_Gunner]

Re: What kind of outdrive...?

That prop is so beat and worn it cant be used a reference or starting point...Heres a start 17p 4 blade..It might be 1 inch off but it is better to be under than over.....

http://boatpropellers.iboats.com/Me...20487/?**********=388867850&*******=880097868

Heres a 3 blade if you run with only 1 maybe 2 people it may be spot on also.
http://boatpropellers.iboats.com/Me...20427/?**********=388867850&*******=880097868

If yoou find the time and borrow a prop (19p) take a run and note the highest speed (gps) and the rpm at top speed post back..You will get a bit more than a WAG..but both of those props should work...The 4 blade 17 is a great all around prop....PS that trim tab order it...very simple to put on

1.That drive is a alpha 1 gen 11
2.No the node is bolted to the drive
3.Is this boat new to you..if so change your water pump...see 3


Some points of intrest

1. http://forums.iboats.com/showthread.php?t=300472
2. Mercruiser Service Manual index and links
3. http://forums.iboats.com/showthread.php?t=409179&highlight=changing+impeller

 

[rauch0812]

Re: What kind of outdrive...?

Prop: What do you mean by "Heres a 3 blade if you run with only 1 maybe 2 people it may be spot on also"?

1. Thanks for the info on the drive!
2. So the fact that mine turns means I should replace it?
3. I'll look into the impeller, thank you!

 

[Tail_Gunner]

Re: What kind of outdrive...?

Prop: What do you mean by "Heres a 3 blade if you run with only 1 maybe 2 people it may be spot on also"?

1. Thanks for the info on the drive!
2. So the fact that mine turns means I should replace it?
3. I'll look into the impeller, thank you!

Sorry about that....You do not have any known perfromance numbers to recomend a prop..".Such as my current prop will push the boat to 50 mph at 4200 rpm ...the prop is a 17p alum 3 blade"...Ohh by the way i usally have 4 people in the boat...(that means weight and drag)

Now if you had those numbers and using some guide lines...it would be possible to suggest a prop that would meet your expectations and be almost dead on in maximizing your boats potential


Your current prop is a bit haggard...worn....old in the tooth...It will not reflect what pitch is needed to dive your boat and be the most effective.....Now if you can borrow a prop in a 19p and do a test run that would be great..Can you?????

Those props i suggested are a guess but a fairly reasonble one......You have a 20' foot boat probably 3400 lbs diven by a 220 hp v8 and probably a 18-20 degree hull.....18p 3 blades are common and 17p 4 blades is almost the same

http://forums.iboats.com/showthread.php?t=409976

Similar boat but he has 50 more ponies...and wants a high performance ss prop

3 blades generally are the best for overall top speed
4 blades provide better hole shots...lower planing speeds and more midrgange power...80% of your boating occurs there....

That trim tab will correct the boat pulling to the right....it functions as a rudder...when the fin is on you simply adjsut the tab by turn it right or left to keep the boat from pulling right or left.....and tighten it down with a wrench...So yes replace it


http://forums.iboats.com/showthread.php?t=250880

Thats a great thread if you can follow those guides line you will learn much about your boat...and boating... Good luck I-boats is full of info and can save you thousands in preventavie care and maintance...

 

[rauch0812]

Re: What kind of outdrive...?

Whew, I'm trying hard to follow all of your info :redface:...

Does it make a difference if I tell you we never have less than 6 people on the boat, usually 8. (Before everyone yells at me the max is 11 persons / 1725lbs and we travel very light on gear and half are children).

Also with the current prop (in it's current condition ) we can get up to 40mph with 6 people in the boat, don't know the RPM's though.

I don't have anybody's prop to borrow, wish we could. I like the idea of lower planing speed, but what does "hole shot" mean? Also, if it makes a difference - I feel like the boat takes forever to plane out and hate how high the bow shoots up in the air... is this affected by my horrible prop? You really have to get up to speed before it finally comes down (just not my preference, makes my stomach drop).

How would I determine the degree of the hull? Would the fact that there is a 33" draft help give an idea of this number? Here are 2 pics of the boat if that helps... (be nice, these were taken before we acid washed her, waxed her, bottom painted, etc.)

I really really appreciate the advice, we are completely lost! Also, I heard you can send away your old prop to be reconditioned... is this one still in good enough shape to get fixed up and keep as a spare on the boat?

 

[rauch0812]

Re: What kind of outdrive...?

The only options I get online when going thru the options to select the right prop is Alpha 1 or Bravo 1... no Alpha 2 anywhere. Are you sure it's an alpha 2?


Also, when I do this propeller wizard thing it suggests a 15 1/4 x 15... does that sound resonable?

 

[oldjeep]

Re: What kind of outdrive...?

The only options I get online when going thru the options to select the right prop is Alpha 1 or Bravo 1... no Alpha 2 anywhere. Are you sure it's an alpha 2?

He said Alpha 1 Gen 2. Not Alpha 2

You are looking for an Alpha 1 prop

 

[oldjeep]

Re: What kind of outdrive...?

I really really appreciate the advice, we are completely lost! Also, I heard you can send away your old prop to be reconditioned... is this one still in good enough shape to get fixed up and keep as a spare on the boat?

Yup. costs $45 at my local prop shop to fix and balance an aluminum prop.

 

[rauch0812]

Re: What kind of outdrive...?

Ahhh... gen II, sorry about that! Makes more sense now .

So, all of these prop calculators based on weights (since I don't know all of the RPM and current prop info) are suggesting either a:

3 blade 15 1/4 x 15 or
4 blade 16 x 15

Should I just order one of these?

 

[Tail_Gunner]

Re: What kind of outdrive...?

http://boatpropellers.iboats.com/Me...20487/?**********=388867850&*******=880097868

I would not waste money on a old worn prop...That 17 should do nicely plz report your results...No prop calcs are not based on weight...

 

[rauch0812]

Re: What kind of outdrive...?

This link below asks about your boat and asks weights... can anybody run their boat info thru it and see if it comes out with the right prop?

http://www.watercraftservices.com/P...nes=1&boatAltitude=1&waterSports=1&cruising=1

In the meantime, I'm waiting to hear back from Larson on Monday with info about what prop was sold with the boat originally.

 

[steelespike]

Re: What kind of outdrive...?

Hole shot is the time it takes to go from no wake to planing.
For all intents and purposes you have a deep V. It will be slower to plane than those with a flatter bottom and will have a slower top end,but will ride a little smoother.
If you have 6 people aboard and 3 are sitting across the back the bow will rise
and be slow to plane.A 17" 4 blade Solas Amita sounds good It will improve hole shot
stay on plane with less power and handle better at the dock.
I also feel it would be better to get your present prop repaired they can tell you the size and you can then do some test runs and get some real numbers.It could then become your spare in the event you decide to change props.