Prop/motor height setup

[CaneCutter79]

Re: Prop/motor height setup

I thought about doing it that way but I was affraid I would damage the lower unit or skeg if the blocks shifted.

Definately do not block the bottom of the skeg right?


Also, since this is hydrollic trim, will the motor try to trim up vs. sliding up when raising the trailer jack up front? I had a 40hp motor do that to me without hydraulic trim when raising a motor on a jon boat.

Again, your responses are very much appreciated. I can't afford to break anything and I want to be well enough informed when doing things like this on my own. THANKS!

 

[hwsiii]

Re: Prop/motor height setup

Since you have hydraulic trim it will not do that. And if you put all of that weight on the skeg it might be a problem.


H

 

[CaneCutter79]

Re: Prop/motor height setup

I raised the motor with blocking on the vent plates as you described. I'm surprised how easy it was. THANKS!

The scary part is, the reason the bolts appeared short at the top and not having full coverage on the nut is because ALL of the bolts were a bit loose. Not really loose but loose enough that it didn't take but just a small amount of torque to break the nuts loose. I tighted the nuts down to have full coverage plus 1/16-1/8" out of the nut. I also applied some thread-locker just to keep that from happening again.

I only raised the motor 1 notch (approx. 1") just to guage "what does 1" higher do" and I also noticed the motor has been this high before so I should be good on water pressure. I'm going to order a guage for sure in case I raise it any more.

Now.....

Off to the lake to run some tests.

 

[hwsiii]

Re: Prop/motor height setup

Cane, I will be here. In my opinion with 95% of all outboards you do not have to worry about water pressure, UNLESS you are running a jackplate on the boat. The transoms are designed so you can't raise the motor too much, if you have the right motor length on the boat, BUT there may be some motors that have more than one intake and the top one is too high.


H

 

[CaneCutter79]

Re: Prop/motor height setup

Cool. I only raise the motor 1 notch just to be on the safe side and so I can try to guage, "what does one notch of lift do". If I gain 50rpm, there's my number. If I gain 100, do not require as much trim, etc, that will tell me if I can or need to raise the motor more.

I also trimed the motor down about where it is when I'm at WOT on plane to get an idea of the water pickups/intakes were to high if I lifted 1". I think I may be about as high as I can get it.

That's why I want to test it first before going any higher. I'll be sure to look at the back of the hull while on plane to see where the ventilation plate is at WOT.

 

[hwsiii]

Re: Prop/motor height setup

I will be waiting cane.



H

 

[CaneCutter79]

Re: Prop/motor height setup

I will be waiting cane.



H

Well just to follow-up, I raised the motor only (1) notch or 1" up from where it was. The boat has less bow lift, more slip, lost 1mph, and the prop does not bite as well.

Amazing what 1" will do.

I'm going to drop the motor back down to where it was and call it good. I really like the increased lift I got from the new prop. It really does ride a lot better with less hull in the water.

Overall, I'm happy knowing that the prop I have performs what I feel the motor should perform like.

I'm going to replace a potentially damaged coil and I hope to pick up a few RPMs from having a damaged wire. I've seen this happen before. My buddy picked up 500 rpm just by replacing a pinched wire on a power pack.

If not, oh well. I'm happy enough now. I'm just glad to have a boat.

 

[hwsiii]

Re: Prop/motor height setup

cane, it appears you have tried as hard as you can to get the maximum you could out of it. I commend you for your efforts in that cause.



H

 

[Sea Rider]

Re: Prop/motor height setup

With proper engine height at transom and correctly trimmed, water flow should pass slight under small upper plate when at full plane on flat waters, check.

Happy Boating

 

[CaneCutter79]

Re: Prop/motor height setup

With proper engine height at transom and correctly trimmed, water flow should pass slight under small upper plate when at full plane on flat waters, check.

Happy Boating

Water is passing more than slightly under. I snapped a few pictures as best I could when testing the new motor height. With the motor raised 1" up from where it was, the water plane was 4-5" below the lower plate yet I still had water pressure. Previously, it was about the same but closer to 3-4" above plane. The new prop was having issues biting and maintaining "grip" similar to the old prop. Before I raised the motor, the new prop was biting well and performed flawlessly. THus, I'm lowering the motor down to where it was and walking away.

See below. (click thumbnails)

With old prop before motor raised 1"



With new prop on plane after raising motor 1"


Quick vid:
[URL=http://smg.photobucket.com/albums/v690/jb_adams/My%20boat/?action=view&current=MotorSetup.flv] [/URL]

Like I said, I think the boat/motor setup is now going to do its very best it can do so I'm done adjusting. The old saying goes, "if it's not broke, don't fix it". If I keep going, eventually something will break and it's not worth that. After all my research, asking questions, etc., I'm happy that the boat is doing what it should.

 

[hwsiii]

Re: Prop/motor height setup

Sea Rider, that picture is wrong, you might want to read this for a better understanding, it is actually the plate below that one that is the anti ventilation plate.

I will have to say though that I NEVER make an error UNLESS I am breathing.


http://forums.iboats.com/showthread.php?t=369057



H

 

[Sea Rider]

Re: Prop/motor height setup

Sea Rider, that picture is wrong, you might want to read this for a better understanding, it is actually the plate below that one that is the anti ventilation plate. H

I know where the anticav plate is located, is the lower big one, if water flow should pass under it in heavy chop, will have bad water engine refrigeration, prop will air/vent with poor cruise speed, what stated on posted picture works perfect for sibs/ribs configurations, should work here too.

I would lower the engine, remain with my existing prop, remove actual doel fin (seems is for a extra long engine application) and replace for a standard horizontal doel fin most commonly used, will work much better.

Every existing engine has it's factory height recommendations parameters as pic example, check parameters for that engine. As nothing is cast in stone, try under trial and error to see what suits you best.

Happy Boating