Did I raise my motor too high? vs Pitch on prop

[sublauxation]

I have early 80's Sylvan 18 ft tinney with 90 etec, hull weight about 1200 lbs. On flat water WOT I got 5100 RPMs and 42mph on GPS with a 13.75 x 17 evinrude AL prop. I was "positive" raising the motor 1 hole would get me to recommended 5500 RPM. This summer I rebuilt the transom and raised it and motor height by 3/4 inch. I never got to test with that prop on flat water for comparison (my boat broke free while moored, drifted into some rocks and banged up the prop ) but it broke loose pretty easily on turns.

My spare is a Turning Point Hustler 13.25X15, on flat water at WOT it gives me 5100 RPMs and 39 MPH on GPS, and it also broke loose easily on turns.

Now the question:
Shouldn't the 15 pitch prop raised up 1 hole have given me a lot more RPMs vs the 17 pitch prop? If you raise it too high will you actually lose RPMs?

Because it breaks loose on turns, I'm assuming I should lower it 1 hole? This sucks because I physically have to cut down the transom and re-weld the cap. I don't want to cut it down if there is an alternative. So much for being "positive".

I ask mainly because the guy who is going to fix my prop will re-pitch it for free when he fixes it, but if I just have it fixed and pitch changed later it will cost me double. I was thinking that re-pitching to 16 may be a good idea since raising the engine didn't seem to get more RPMs.

I also have a 15 pitch SS prop, is that likely to break loose on turns at the higher motor position just like the AL props? I haven't tested it because it has a couple small nicks I want to fix first, but same thing goes with changing pitch and price. In theory I thought 16 would be about right.

Thanks for any and all opinions.

 

[bob johnson]

Re: Raise motor height to0, high and change pitch?

Re: Raise motor height to0, high and change pitch?

I have early 80's Sylvan 18 ft tinney with 90 etec, hull weight about 1200 lbs. On flat water WOT I got 5100 RPMs and 42mph on GPS with a 13.75 x 17 evinrude AL prop. I was "positive" raising the motor 1 hole would get me to recommended 5500 RPM. This summer I rebuilt the transom and raised it and motor height by 3/4 inch. I never got to test with that prop on flat water for comparison (my boat broke free while moored, drifted into some rocks and banged up the prop ) but it broke loose pretty easily on turns.

My spare is a Turning Point Hustler 13.25X15, on flat water at WOT it gives me 5100 RPMs and 39 MPH on GPS, and it also broke loose easily on turns.

Now the question:
Shouldn't the 15 pitch prop raised up 1 hole have given me a lot more RPMs vs the 17 pitch prop? If you raise it too high will you actually lose RPMs?

Because it breaks loose on turns, I'm assuming I should lower it 1 hole? This sucks because I physically have to cut down the transom and re-weld the cap. I don't want to cut it down if there is an alternative. So much for being "positive".

I ask mainly because the guy who is going to fix my prop will re-pitch it for free when he fixes it, but if I just have it fixed and pitch changed later it will cost me double. I was thinking that re-pitching to 16 may be a good idea since raising the engine didn't seem to get more RPMs.

I also have a 15 pitch SS prop, is that likely to break loose on turns at the higher motor position just like the AL props? I haven't tested it because it has a couple small nicks I want to fix first, but same thing goes with changing pitch and price. In theory I thought 16 would be about right.

Thanks for any and all opinions.

must be the design of the turning point...I would think youd go way past 5500 with that SS

I had a 14 x17 aluminum OMC prop on my 115... it would give me 5400 at wot..I put the SS omc 13-3/4 X 15 on it I could pull 6200 rpms at wot..and gained 1.5 MPH!!!

ss really is a different animal

I not have a 13-3/4" X 15 brand BRP aluminum prop...wide blade( were the 14 x 17 was a narrow blade) and I pulled 6000 rpm at wot.....but i really dialed in the trim.....but my boat has flotation pods that are dragging while on plane..so it kills my spped and probably has an effect on my rpms

i had nothing but good stuff about turning point props...was there an upside????

hole shot?

where is you cav plate in relation to your hull bottom?


I have a jack plate and I can drive it up 3 " from level with the hull and still maintain wot and not wash out....

dont know much about the turns....


bob

bob

 

[sublauxation]

Re: Raise motor height to0, high and change pitch?

Re: Raise motor height to0, high and change pitch?

Now the plate is about 3 inches above the bottom of the hull, that's why I was confident of being able to raise it up. Hole shot was maybe a little better with the Hustler 15 pitch, but I should have had higher RPMs. People do seem to love those props, that's why I'm confused by the low RPMs.

Didn't wash out when going straight, just cornering, is some of that to be expected?

Maybe I should just bite the bullet, get the SS cleaned up and test it. It's actually in really good shape but I'm not sure how big a nick it takes to effect performance for accurate comparison.

 

[bob johnson]

Re: Raise motor height to0, high and change pitch?

Re: Raise motor height to0, high and change pitch?

I am not sure id want a permanently mounted motor 3 " above the bottom of the hull.

when the weather gets rough youd be washing out contantly...and you probably couldnt back up in reverse as good as if it was even with the hull.

my motor is on a 10 " setback...so I should be able to use it a little higher...


bob

 

[sublauxation]

Re: Raise motor height to0, high and change pitch?

Re: Raise motor height to0, high and change pitch?

I'm assuming yours' is on a jack plate? Does that set-back make the transom sit quite a bit lower in the water? I've considered one but it would make an even tigher squeeze into the garage.

Logically I'm thinking I should cut my transom back down and lower the motor, then try the SS prop to get my RPM's where they belong. Frustrating because I thought this was going to be the perfect set up finally.

 

[bob johnson]

Re: Raise motor height to0, high and change pitch?

Re: Raise motor height to0, high and change pitch?

I'm assuming yours' is on a jack plate? Does that set-back make the transom sit quite a bit lower in the water? I've considered one but it would make an even tigher squeeze into the garage.

Logically I'm thinking I should cut my transom back down and lower the motor, then try the SS prop to get my RPM's where they belong. Frustrating because I thought this was going to be the perfect set up finally.

cutting is a drastic reaction.... I thought you moved your motor UP....

I am wonder why you wouldnt be able to get your motor set up close unless your motor length doesnt match your tranom....or you have some odd boat....

my motor is on a hydraulic jack... generally pushing the weight back would leverage the stern down into the water, and i anticipated that and welded on blig flotation pods on the rear...but the result was that the pods are barely in the water ...because the boat floats so shallow anyway....

is has a huge wide foot print, and isnt too heavy... so it takes a LOT of weight to push it down....

bob

 

[sublauxation]

Re: Raise motor height to0, high and change pitch?

Re: Raise motor height to0, high and change pitch?

When I rebuilt the transom I removed most of the splashwell to make a casting deck, I didn't want to sink so I added more height than original to raise the new transom to sit tight under the motor with it 1 hole higher than originally set. Now to lower the motor I have to cut it back down.

What size boat do you have? How much lower do you think the stern sits? What have been the advantages of that large set back? I was considering a 5 inch or so jackplate and that would certainly help out some.

 

[bob johnson]

Re: Raise motor height to0, high and change pitch?

Re: Raise motor height to0, high and change pitch?

What size boat do you have? How much lower do you think the stern sits? What have been the advantages of that large set back? I was considering a 5 inch or so jackplate and that would certainly help out some.

I have a 20.5' Lowe Ultra Roughneck, Mod V
it has a 12 degree hull so it really isnt close to a flat bottom...

I bought the jack plate for being able to motor in shallows and then adjust when i wasnt in the shallows. I got the deep set back because it was said at speed the water rises after it leaves the transom and thus I could maintain a higher prop even at WOT.

with my low draft i dont think the 10" setback cause me a 1/2" of draft...

I added buckets of water and set them at the transom before I installed the motor and jack to get an idead what 300 lbs would do to the draft...

the waterline was at the chine 72" of width...after I installed the jack and motor, and my pods...the water line is about the same spot on the chine. of course i have the flotation pods...BUT the outer edge that ends at the chine isnt under water!!!!

I have about 4/5th of my pods out of water!!! the transom just didnt sink like I had thought

but each boat is different...if you transom is way low, pods will help and if you boat isnt very long a deep set back jack MAY hurt..MAY not


bob

 

[sublauxation]

Re: Did I raise my motor too high? vs Pitch on prop

Did you always have the jack plate on? If not, did you notice much difference? Thanks for your info! I've considered putting one on even before rebuilding my transom but am somewhat afraid of adding one more variable to my mess in trying to get propped right. Does your have power adjustable height or manual?

 

[bob johnson]

Re: Did I raise my motor too high? vs Pitch on prop

Did you always have the jack plate on? If not, did you notice much difference? Thanks for your info! I've considered putting one on even before rebuilding my transom but am somewhat afraid of adding one more variable to my mess in trying to get propped right. Does your have power adjustable height or manual?

I never ran my boat with out the jack...

id say that the jack would make it easier to solve your power problems..

it isnt all in the prop!!!!!!!!!!!!!!!!

you have to set the rig up for the prop to do its job, then trimming will change a lot...

you have to get the prop in clean water....


with a hydraulic jackplate you can try any setting height you need to find a sweet spot...


PLUS it allows you to do other things as, like raise it way way up.....when you are just putting along in the super shallows... like getting away from shore in shallow flats, with out poling so far!!


if one was worried about set back you could get the smallest set back..maybe 4"... that wont change much...


bob

 

[steelespike]

Re: Did I raise my motor too high? vs Pitch on prop

If your not on a jack plate 3" is way high.Typically the antivent plate ends up about 1" above the bottom.It should be visable on plane but not in mid air.You are refering to the plate just above the prop?
The Hustler is a very agressive prop and resists venting really well.Being agressive it also holds down rpm more than expected.There is evidense that the Hustlers are also unpredictable even making some wonder if miss marked.
A 4 blade prop may help.I've seen the Solas Amita 4 blade do well raised.

 

[sublauxation]

Re: Did I raise my motor too high? vs Pitch on prop

Thanks Steelespike
I can cut by transom back down to origina and lower the motorl, A jack plate would be easier but I'm hesitant to add lenght to the boat, hard to fit in the garage. Any ideas on what I can expect if I added one...performance, more or less water coming over the back?

Are Hustler props unpredictable from one to the next even of same pitch?

I've heard of people putting etecs up that high and higher, that's why I raised mine, thought it would make my RPMS fall in perfect. In hindsight, they probably had jack plates and could lower them as needed.

You mention the Solas...any pitch recommendations?

 

[sethjon]

Re: Did I raise my motor too high? vs Pitch on prop

I have early 80's Sylvan 18 ft tinney with 90 etec, hull weight about 1200 lbs. On flat water WOT I got 5100 RPMs and 42mph on GPS with a 13.75 x 17 evinrude AL prop. I was "positive" raising the motor 1 hole would get me to recommended 5500 RPM. This summer I rebuilt the transom and raised it and motor height by 3/4 inch. I never got to test with that prop on flat water for comparison (my boat broke free while moored, drifted into some rocks and banged up the prop ) but it broke loose pretty easily on turns.

My spare is a Turning Point Hustler 13.25X15, on flat water at WOT it gives me 5100 RPMs and 39 MPH on GPS, and it also broke loose easily on turns.

Now the question:
Shouldn't the 15 pitch prop raised up 1 hole have given me a lot more RPMs vs the 17 pitch prop? If you raise it too high will you actually lose RPMs?

Because it breaks loose on turns, I'm assuming I should lower it 1 hole? This sucks because I physically have to cut down the transom and re-weld the cap. I don't want to cut it down if there is an alternative. So much for being "positive".

I ask mainly because the guy who is going to fix my prop will re-pitch it for free when he fixes it, but if I just have it fixed and pitch changed later it will cost me double. I was thinking that re-pitching to 16 may be a good idea since raising the engine didn't seem to get more RPMs.

I also have a 15 pitch SS prop, is that likely to break loose on turns at the higher motor position just like the AL props? I haven't tested it because it has a couple small nicks I want to fix first, but same thing goes with changing pitch and price. In theory I thought 16 would be about right.

Thanks for any and all opinions.

If you raise it too much you won't get on plane. The 15 should go about 400 RPM more

 

[sublauxation]

Re: Did I raise my motor too high? vs Pitch on prop

That's why I'm a little confused. I raised the motor thinking I would get to proper RPM with my 17 pitch prop. That didn't seem to happen, but dinged the prop before proper testing. The 15 pitch should have gained 400 RPM but didn't. I expected to gain even more since I also raised the motor up.

The boat still goes on plane instantly even at higher position. Should I expect some ventilation when turning?

 

[bob johnson]

Re: Did I raise my motor too high? vs Pitch on prop

That's why I'm a little confused. I raised the motor thinking I would get to proper RPM with my 17 pitch prop. That didn't seem to happen, but dinged the prop before proper testing. The 15 pitch should have gained 400 RPM but didn't. I expected to gain even more since I also raised the motor up.

The boat still goes on plane instantly even at higher position. Should I expect some ventilation when turning?

raising it a little and raising it 3 " are two different things.

did you read someplace that 3 " might help somehow???

like many things, one piece of the recipie doesnt make the dish...you need all the recipies in the exact measure to acheive the desired results.

good luck

bob

 

[steelespike]

Re: Did I raise my motor too high? vs Pitch on prop

Some people accept some venting in turns to get that little bit more speed but it appears you haven't really gained much if any.A jack plate gets the motor in cleaner water allowing higher setup and of course allows finer adjustment.
Don't forget the Hustler is very agressive and might not gain as much rpm as the rule of thumb indicates.The best I can describe the Hustler is "unpredictable" results.I would add that the problem if any isn't wide spread or we would be hearing a lot more aboutr it.If your antivent plate was visable on plane or about 1" above the bottom raising it wouldn't add nearly as much as that which was say 1 or 2" below.
Too much height could also create slip problems flattening performance.

 

[sublauxation]

Re: Did I raise my motor too high? vs Pitch on prop

raising it a little and raising it 3 " are two different things.

did you read someplace that 3 " might help somehow???

like many things, one piece of the recipie doesnt make the dish...you need all the recipies in the exact measure to acheive the desired results.

good luck

bob

I like the recipe analogy! Unfortunately I started cooking this dish last year and still haven't gotten it right, but getting closer.
I only raised it 1 hole, I think about 3/4 inch, it was about 2 inches above bottom before. I've heard from a lot of people that they have theirs 3-4 inches high, so thought I was moving in the right direction.

Thank you guys for all your help, it's helping me get closer.

Makes sense that if the motor was mounted pretty high to begin with there wouldn't be as much gain in RPM, combined with my Hustler prop acting more like my 17 pitch evinrude prop or slipping a bit due to height.

Going to my prop repair guy today, will fix up my 15 pitch stainless and try that at the current height and hope it works like magic, maybe look into that Solas prop Steelespike mentioned also. I don't like the venting so if that doesn't work I'll either chop the transom back to original and drop the motor 3/4 inch or look into a jack plate. Top speed isn't my main concern, just wanted to make sure I"m in the right RPM range.