How to check your OB motor height & wear the right prop!

Wow, what a great read! I'm making this post a sticky ...

See: http://www.veradoclub.com/smf/index.php?topic=137.0

I like it.
Thanks!

On bracketed motors this method can be pretty tricky.

That being said, I spent about two hours today running around with our new Honda engine playing with trim, tabs, and testing different props.

Here is where the water line is when she is up on plane and running well:



If I trim the motor up, the tail end of that plate above the prop just peeks above the water (and the prop ventilates in turns). Is this where it should be?

The motor is mounted on the third hole from the top (same as the Ox66 that came off).

outstanding info, thanks.

SBH2OMan":2fa6dhpd said:

Here is where the water line is when she is up on plane and running well:

If I trim the motor up, the tail end of that plate above the prop just peeks above the water (and the prop ventilates in turns). Is this where it should be?

Click to expand...

That should be purrrrrrrrrfect !

If I trim the motor up, the tail end of that plate above the prop just peeks above the water (and the prop ventilates in turns). Is this where it should be?

Click to expand...

I'd be wanting to try it 1 hole higher, so the whole plate is out of the water. I wouldn't worry about the blowing out in the turn so much. Trim in or slow down.

But for what I'm saying it may or may not be to your liking. Still I try to wring every bit of fuel millage I can get out of it.

Still It's easy enough to satisfy the curiosity.

Can't wait to raise mine....same situation.......it's too deep.

I'm going to run a few more times to be sure, but the top plate is definitely swimming when I'm planed up.....

I can't tell you guys how much I appreciate this group. The information is unbiased, detailed, and extremely helpful.....I gotta get a few pictures, and post on the introduction tab...

Thanks

warthog5":tgs8z7tn said:

I'd be wanting to try it 1 hole higher, so the whole plate is out of the water. I wouldn't worry about the blowing out in the turn so much. Trim in or slow down.

Click to expand...

I added that emphasis, but I remain stunned how many boaters don't realize that for best OB performance, it should be mounted as high as practical and that given that ... one needs to trim her in before undertaking an aggressive turn.

Ludicrous40":tgs8z7tn said:

I can't tell you guys how much I appreciate this group. The information is unbiased, detailed, and extremely helpful.....I gotta get a few pictures, and post on the introduction tab...

Click to expand...

Thanks for the kind words! We are afterall ... your on-line Parker boat Owner's Manual.

But note, some us are indeed biased ... just a few of mine listed below:

ALL BOAT MAKES - RANT #1: The OB wears the wrong prop

ALL BOAT MAKES - RANT #2: The OB is set way too deep

ALL BOAT MAKES - RANT #3: The stock OEM trim tabs are way too small ...

Started the experimentation yesterday after raising the motor one hole position (it was as deep as they go). My goal is fuel efficiency.

I have a 2003 2520XL with F225 on a bracket. Factory Lenco Trim tabs. Prop is a standard Yamaha stainless (15x17-T)

2 People on board, ~ 100 gallons fuel, ~ 300lbs gear/ice overall.

Conditions: Flat following seas, tabs up, trimmed motor up to where the RPMs were a little unstable due to conditions, then just down to a stable RPM. Variation in the RPM and speeds shown below were a result of traveling over the swells.

WOT 5300 to 5400
Speed 27 to 28

FYI @ 4800 to 4900
Speed 24 to 25

Observations: Someone had already raised the motor 2 hole positions, and dropped it back down again. While driving/trimming it was definitely quicker to cavitate, but I guess that makes sense. I'm assuming that the pictures indicate that it is still too low? I could just barely see the back of the plate...at times....

Am I doing this in the right order, given the three factors: Motor height, Prop, Tabs????

Ludicrous40":z4e4bzji said:

Started the experimentation yesterday ...

Am I doing this in the right order, given the three factors: Motor height, Prop, Tabs????

Click to expand...

No, I would pick your best prop 1st and dial in the motor height specifically for that prop. And before I set or adjust trim tabs, I make sure the OB is dialed in at the trim position I need for best performance. Then set the trim tabs to the sea state.

I think if more Dealers were willing to tell new boat owners, "Hey buddy, remember that you need to trim this motor IN before making any turns" ... then you'd see most motors mounted at the ideal height.

Dale, thanks for the quick reply.

I know you're a big fan of the 4 blade, do you have any suggestions based on that, or should I just seek the advice of the Prop Gods?

It just seems like I should be able to run a 24kts at a lower rpm....IMO

If you have trim tabs, do you check the height with the tabs down and again up, so just down?

[Dale Wrote:]
No, I would pick your best prop 1st and dial in the motor height specifically for that prop. And before I set or adjust trim tabs, I make sure the OB is dialed in at the trim position I need for best performance. Then set the trim tabs to the sea state.




Not quite sure how to re-post someone else's comment

Just my two cents worth, I have a 2520xl with a f250 on a bracket and when I got her the motor was all the way down. Picked her up two holes and it made a huge dif in fuel burn and speed, so I tried one more hole making the motor all the way up. While cruising the plate was exactly where it needed to be but I actually lost some speed and fuel burn. Lowered the motor back down one hole and she seems to love it there. That's with a rev 4 prop.

What are the specs on your rev4 prop. I have the F225 with factory 3x15x17prop. Am planning to try recommendation from PropGods:

Quicksilver thunderbolt : 3x 15 3/4 x 15

Tried out a 17p rev 4 today On my bracketed 2300/F250. This is at 28mph 4200 RPM cruise trimmed with light tabs.

Ludicrous40":1y7mfxt2 said:

Not quite sure how to re-post someone else's comment

Click to expand...

Just hit the "Quote" button at the bottom right of any comment you want to quote, then edit to your choosing before adding your comment and selecting "Submit".

ryanc2":eanc8bcc said:

Tried out a 17p rev 4 today On my bracketed 2300/F250. This is at 28mph 4200 RPM cruise trimmed with light tabs.

Click to expand...

Still looks a little to low Ryan. By the way, check out GROUPERJIM's post on his 2320 with the F250. He has some good data on props. He ended up going with the Mirage Plus 15 3/8 x 18. I'm thinking about going with that one too but I'm going to raise my motor first and see how that works out. Also thinking about a Permatrim if raising the motor doesn't eliminate my porpoising issue. Don't really expect it to though?

This topic is really confusing. My 2300 CC with a F250 seems to be very sensitive to every adjustment, I assume OB height is no different.

It's still new to me because I've spent most of my time on my 2520 with IO diesel where adjustments seem to have little influence. My outboard is certainly more sensitive.

On my 2300, CLEARLY there's some adjusting to do. I'm reading my butt off on the topic because I don't want to make things worse and found Dale's post to be a GREAT read. …

http://www.veradoclub.com/smf/index.php?topic=137.0

In fact, after reading the article, I feel a lot better about attempting to figure out my engine height. And just when I'm feeling better about it, you throw me a curve ball Dale.

The very first words of the article you shared and in BOLD text…

Before you start messing with props, you must get the engine height right.

Then you post…

No, I would pick your best prop 1st and dial in the motor height specifically for that prop.

I have some additional challenges, primarily I have a kicker motor which causes the boat to lean to that side. I try to load the boat to offset that lean but it's always there. If I don't use my trim tabs, the boat will definitely lean and how will that effect determining OB height?

The kicker is a necessary evil. I had a diver in the water, in extreme current and lost my primary motor one time. I was very lucky I was able to eventually get it started but not as lucky as that diver was! I use this boat in Mexico where there is no on water assist. The kicker really is a necessity.

So now I'm back to being uncertain where to start this process again.

Also, why would you try to determine OB height with 50% fuel and a moderate load? What will happen to OB height when you have a full fuel load and excessive weight? Would it be better to determine OB height with the boat loaded as it will most often be used?

What is the worst that can happen if the OB is to high?

Otolith, I think the most consistent theme here is to get the motor hight correct. Most of us don't have a lift at our disposal and need to take our boat to a shop to have the motor raised. That said, I just don't have the luxury to go back and forth too much. I'm going to go ahead and raise mine first because I'm fairly confident that it needs to be done no matter what prop I have. Also, based on what others here have done with like boats, I'm going to raise mine to the top hole. Then I will begin changing props. If I have to go back and lower 1 hole after that then that's what I'll do. See pic below where mine rides currently. Dale's posted article, especially the photos are very helpful demonstrating what the correct look should be.