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Another prop seaker, New F50 on Classic 15'3
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| blacksmithdog |
Posted on 04/09/13 - 3:13 PM
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So, my Yamaha F50 is sitting all the way down on the transom, it is obviously too low. What is the proper relationship height wise of the cavitation plate to the bottom of the keel on a 15' Whaler?
Thanks
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| Westcoaster |
Posted on 04/09/13 - 10:29 PM
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From what these guys have told me minimum 2 holes up, preferably 3, there many things to consider, stay tuned and i'll let you know how mine works out 3 holes up, definately higher for 4 strokes,i do have a new motor and need to break it in properly first. What kind of setup do you have ? What year hull, center console, side helm, prop pitch etc. ?
How does yours ride right now ?
Handling, planing etc ?
Edited by Westcoaster on 04/09/13 - 10:34 PM |
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| blacksmithdog |
Posted on 04/10/13 - 4:43 AM
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Mine is a 1992 15' GLS, I guess you'd call that a side console.
I'm running a stainless 10.5X12 prop, I think it's a Yamaha.
I get around 5500 rpm's if I play with the trim, and with two people in the boat.
It does 32-33 mph per the GPS.
It seems to come out of the hole slowly, and not plane quickly.
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| tedious |
Posted on 04/10/13 - 4:46 AM
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blacksmithdog wrote:
So, my Yamaha F50 is sitting all the way down on the transom, it is obviously too low. What is the proper relationship height wise of the cavitation plate to the bottom of the keel on a 15' Whaler?
Thanks
It depends on the prop. If you're running a decent, modern stainless steel prop (and you should be) I would start with the AV plate about an inch above the keep line, and see how she goes. That will probably be either all the way up, or one hole down from that top position.
Tim
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| Westcoaster |
Posted on 05/06/13 - 3:21 PM
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Finally had the boat out for a sea trial and break in procedure,
i spent quite some time repairing old stuff i been meaning to clear up, also reconfigured the deck layout etc,
12 gallon gas tank up front, battery on port side 6' from stern and was able to move my seat forward better than a foot all to compensate for the heavier weight of the new 4 stroke, also new wiring, fuses,bilge,battery,fuel tank & hose and nonskid paint.
Once launched i noticed it sits very nice in the water, not stern heavy
break in procedure calls for 2,000 rpm in the first hour or about half throttle, second hour says increase throttle enough to put on plane then back off and maintain plane. i had nothing but problems finding out how to wire a round yamaha tach with the tiller handle, the needed hub is being used by the manual rpm adjustment in tiller, , I called Yamaha Canada and USA aswell as many service centers and got nothing but conflicting part #'s and procedure, NOBODY knows how this is accomplished ? so opted for a cheepy from yamaha, the kind which wraps around spark plug wire which i now know is inaccurate, shows 1200-1500 at idle and around 4,000 at half throttle. Very dissapointed as i would like accurate rpm.
Anyways i just used the throttle position indicator on the throttle grip as my reference, half throttle put me on plane which was surprising to me, so i just backed off a little to maintain it, this was trimmed all the way down or in, boat speed was 22-24 mph on gps, after the first hour i increased speed about another 1/8 - 1/4 and ran it for another 45 mins varying speeds slightly between 25-30 mph, 30 mph was under 3/4 throttle and bow stayed down nice and steady, then i played with trim a little, i can't trim out very far before cavitation starts, i had a couple quick looks down at the leg while cruising and could easily see the anit ventilation plate above the prop, although its hard to determine if the rear of plate sits above water and by how much, i am using the Stiletto 12x11 recommended by Tom, seems to be a good fit from what i can tell so far, the stern lifting ability of the prop worked better than expected, but then again i only weigh 175 lbs and the boat is well ballanced now.
All said and done i was very surprised how easily the boat planes but worried about the cavitation, the boat seems fine trimmed all the way in or a hair out, next trip i can run WOT for short intervals.
We will see how the next trip goes and decide if i might want to change the mounting position, its 3 holes up now ( highest position for the 2013 50HP Yamaha 4 Stroke LHB)
my first post indicated a 2012 but ended up with the 2013
just figured i would clear that up.
Edited by Westcoaster on 05/06/13 - 3:40 PM |
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| dgoodhue |
Posted on 05/06/13 - 8:17 PM
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You probably don't want to hear this but I think you have too much weight forward. I have this problem if I have too many passengers in the front. IMO the 15' like the weight rearward. (or atleast in the stock position). The static might look perfect but the best weight distribution for.performance isn't always with a level static trim.
50hp 4 stroke is no heavier than any of the 2 stroke 70hp motor the boat was designed for. If your fuel tank is movable try temporarily putting that in the back to see how you boat responds.
Dave |
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| Tom W Clark |
Posted on 05/06/13 - 8:41 PM
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I have yet to hear of anybody needing to lower a motor with the Star, but maybe a 15 Standard is one example of a set up that needs the motor a little lower.
You are really going to need a tach (at least for initial testing) to figure out if the pitch is correct or not.
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| Westcoaster |
Posted on 05/09/13 - 10:18 PM
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Yup i'm gonna have to lower it it some, was out again this evening
Flat calm, can't trim out at all, tight turns causes cavitation aswell,
WOT put me @ 33-34 mph trimmed all the way in.
What does it sound like when you hit the rev limiter ?
Don't think i hit it but just curious
Edited by Westcoaster on 05/09/13 - 10:22 PM |
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| tedious |
Posted on 05/10/13 - 5:04 AM
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I'm with Dave - I think you've got a good deal too much weight forward. You mention you did that to compensate for the greater weight of the 4-stroke, but your F50 weighs 249 pounds, actually a bit less than the classic OMC triple that many of the 15s were originally powered with. If you're ventilating so badly so you can't use the trim at all, something very basic is wrong.
I have not seen the pictures of your setup - what can you easily move back to give that a try?
Tim
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| Westcoaster |
Posted on 05/10/13 - 3:57 PM
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Ok first of all i want to point out i appreciate all the feedback, info and suggestions, love this site.
I googled the serial and model from the motor i pulled, i could not find a match for that model but the closest ones were around 195 pnds, it was an early 80's Evinrude (super) 55 Commercial Model CE55RSLV, definately lighter than the new power as i just pulled the bolts and lifted it off myself ( i weigh 175 )
Besides the motor these are the things i changed
battery used to be tucked behind my seat on the rear starboard,
It now sits on the port side 6' or so from stern.
I used to pack two 6 gallon tanks which sat mid deck, one port and one starboard, now i have one 12 gallon fastened to deck right behind the bow locker.
Moved my seat forward 12" or so
Thats it for changes
For the first few trips i never had the gas tank full, maybe 8 gallons to start with, but lastnight on my way in i only had a couple gallons at most but still had the cavitation.
I will upload a few pics of the setup in a bit, although i never took a picture as it sits in the water but will get some next outing
Sure like to get things figured out
Edited by Westcoaster on 05/10/13 - 4:54 PM |
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| Westcoaster |
Posted on 05/10/13 - 5:13 PM
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These are the only pics i have from the old setup
http://s67.photobucket.com/user/vanbo...mp;page=1#
New setup
while taking the photos i noticed the trim tab on the anti ventilation plate has a square shaped opening cast into it facing forward which looks like it would scoop up water and cause turbulence, why is this needed ?
http://s67.photobucket.com/user/vanbo...amp;page=1
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| Westcoaster |
Posted on 05/11/13 - 10:24 AM
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i will try running it with the fuel tank at the stern but the more i read the more i'm thinking its simply just mounted too high, i can actually see the air being blown out the back under the anti ventilation plate when i try trimming out. I do have another prop to try but hope to get this one dialed in.
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| Tom W Clark |
Posted on 05/11/13 - 10:38 AM
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I doubt you have too much weight forward. I think the motor is too high for that propeller.
You are suffering ventilation, not cavitation. The Star has a large diameter so the blades tips are going to break the surface more.
I'd lower the motor one hole and see how it does. I would not spend money on anything else until you play with the mounting height, but it is important to get a tack, even if only renting a diagnostic tach, to get the WOT RPM.
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| Westcoaster |
Posted on 05/11/13 - 2:57 PM
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Oh i didnt know i had the option to rent one, how do they normally connect ? I still can't get over the fact that nodody seems to know how to hook up a permanent accurate tach to my motor, its driving me nuts.
I'm in a small community and finding anything of use here is dam near impossible but i will try again as i realize the importance
Edited by Westcoaster on 05/11/13 - 2:59 PM |
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| Tom W Clark |
Posted on 05/12/13 - 10:53 AM
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Diagnostic tachometers can use optical (laser), infrared, or acoustic signals. They do not necessary connect to the motor at all.
The difficulty with them is you need to run the motor with the flywheel exposed, so it may be awkward or dangerous to try using one.
Why can't you just unplug the trolling speed control to temporary plug in a tach?
While your digital tachometer may be inaccurate, it *may* be precise. In other words, if it is off by say, a factor of two (which is my guess) you can still use it but know you need to divide by a constant to get your true RPM. My guess it is simply measuring twice the true RPM. What did it read at WOT?
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| Westcoaster |
Posted on 05/12/13 - 11:35 AM
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Digital read around 8,500 but will have to have another look to confirm, i have emailed Yamaha Canada and US again asking for some assistance and just waiting to hear back, thats a good idea unplugging the rpm controller, problem is i don't have the tach or any harness, i should be able to get this figured you would think, there is a multi hub connector aswell so i should be able to have both working together, just wanna confirm before i purchase, i will try changing the # of wraps around the lead wire with the cheapy aswell and see how that goes.
Edited by Westcoaster on 05/12/13 - 11:49 AM |
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| Westcoaster |
Posted on 05/13/13 - 2:13 PM
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Motor is now lowered to 2 holes up position
I am actually making a little progress on the Yamaha tach aswell, seems there is tiller handle for Canada and a different one for USA, Canadian version requires a mod before the tach can be fitted,
still waiting to find out what the mod is.
It will be a few days before i can go for another test run
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| dgoodhue |
Posted on 05/13/13 - 2:50 PM
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I looked at your pictures. Running alone you shouldn't have any weight issues. I bet dropping the motor 1 hole or changing to more toleran surface prop will resolve your issues.
Dave |
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| Westcoaster |
Posted on 05/23/13 - 1:00 PM
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Was out on the water again lastnight for the first time since lowering the motor one hole, dropping one hole made a bigger difference than anticipated.
I was able to trim out enough to make the bow rise and increase speed an extra mph or two, i think its still slightly high but will put some hours on like this, i cannot drop the motor anymore as the spacing from top to bottom transom holes are drilled with 6 1/2" spacing, my only other option is to drill holes in the motors lower mounting plate 3/4" above the top of existing lower bolting slot.
I will do more testing, it was pretty choppy lastnight but i was able hit WOT a couple times tucked in behind a small island, i saw 35+ mph a couple times.
I thought i was making some ground with Yamaha lately trying to figure out how to mod my tiller handle to accept an accurate Tach, they have stopped returning my emails. The cheep tach a have wrapped around a lead wire is unreliable, at idle it shows 1,00-1,250 with the throttle backed right off, my motors manual says the trolling idle is adjustable between 600-900 rpm using the buttons on tiller arm, i can adjust idle up to the point where my tach reads around 1,300-1,350, then pushing rpm up button dosnt do anything so i know i'm around 900 actual rpm.
However at 25 mph cruise on gps the tach reads 4,800-5,500, WOT was more inconsistant, first time i hit wot tach read 5,500, second time it jumped to 6,700 and never bothered to look after that.
So since i am able to hit 35+ im asuming i must be close to the right propping and mounting height, without accurate rpm i just cant be sure but has to be close i would think, although i think if i could trim out just a little more i could get 37 mph out of this motor.
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| dgoodhue |
Posted on 05/23/13 - 7:15 PM
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I think your spot on for what I would expect from a 50hp motor on classic 15'.
Dave |
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