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2004 Honda 50hp
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| rjstox1 |
Posted on 07/13/13 - 8:41 PM
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My 2004 Honda 50 hp carbureted outboard runs rough at high rpm's. Midrange is smooth. Tried gas treatment and techron with no success. Replacing spark plugs when they arrive. Any guesses as to what the issue might be? Thanks
Edited by Joe Kriz on 07/13/13 - 11:45 PM |
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| tedious |
Posted on 07/14/13 - 3:25 AM
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Most likely dirty carbs. When was it last running OK?
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| rjstox1 |
Posted on 07/14/13 - 3:46 AM
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Just bought this used engine a couple of weeks ago. The engine came off a pontoon boat in New Hampshire. I think you are on the right track and I hope the Techron will help clean the carbs. I have only run about 3 gallons of gas through the engine since I have had it installed and I hope more use will take care of the problem. As long as it runs strong from the mid range to about 80% of full throttle, that is acceptable for now. My 1984 Sport really moves even with 4 people on board. if you can think of any other possibilities that a DIY'er could take care of, let me know. Thanks for all input on the matter.
Edited by Joe Kriz on 07/14/13 - 10:42 AM |
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| tedious |
Posted on 07/15/13 - 6:35 AM
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Rebuilding carbs is well within the capabilities of a do-it-yourselfer. It's not that much harder than changing out plugs, just more parts to keep track of.
Another thought - do you have a tach in your setup? You mentioned the motor performs very well in the midrange, even when heavily loaded. I am thinking you may be significantly underpropped and hitting the rev limiter. Typically the rev limiters work by dropping ignition cycles (and on a fuel injected moter, injector cycles too) so it would have the effect of running rough at high speed.
Let us know what prop you have on there, the top speed, and top RPM if you have it.
Tim
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| rjstox1 |
Posted on 07/15/13 - 8:34 PM
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No tach yet......I never thought of the possibility of a rev limiter. Installing Lowrance elite 5 this weekend and the tach will be a project for a couple of weeks in the future. Will let you know when all equipment installed. Thanks for all advice.
Edited by rjstox1 on 07/15/13 - 8:35 PM |
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| Joe Kriz |
Posted on 07/15/13 - 8:37 PM
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One of the most important gauges/instruments is a Tachometer.
Every boat should have one.
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| tedious |
Posted on 07/16/13 - 5:16 AM
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RJ, did you just leave on the same prop that was used when the motor was on the pontoon boat? I am sure a 'toon would not go as fast as your 15, so if you just reused it, that may well be your problem. In any event, you'll want a tach on there to help you figure out the correct prop.
Tim
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| rjstox1 |
Posted on 07/17/13 - 9:50 PM
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Prop was changed out by Owens Marine of NH......it is the correct one........Just installed a Lowrance Elite 5 today and will be shopping for a tach Friday.......Any idea what the red line is for my Honda 50hp? Thanks to all.
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| tedious |
Posted on 07/18/13 - 5:01 AM
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Current Honda 50 has a full-throttle range of 5500-6000 RPM. That means they want to have your RPM in that range when wide open, lightly loaded, for best performance. Usually the rev limiter is set a little above the redline. The gear ratio is 2.08/1. I don't know if those figures are the same for your older Honda - you may need to check with a dealer.
No offense to Owens Marine, but not everyone knows how to pick a prop, and in any case it sometimes takes some trial and error to get it right. If you can describe the prop that's on there, you'll probably get some good advice here.
Also, where was the motor mounted on the transom? Many dealers slam them all the way down, and that's not correct with modern props.
Tim
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| rjstox1 |
Posted on 07/19/13 - 3:51 AM
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Thanks Tim......off to get a tach today.....in regards to the prop.....I am not sure how to detail the props characteristics........When it was swapped out, there was magic marker writing on a blade that indicated this was a Honda prop......I took that as gospel as I do not know otherwise.......I will say that the boat gets up on plane really well so I think the prop is ok......it was the rough running at high rpm that was the problem and without a tach, I do not know if I was pushing the engine too hard and the rev limiter kicked into play......hopefully, after the new tach is installed, it will correct my throttle technique.......I recently changed the plugs and found one that was cracked. Waiting to go for a ride Sunday and see if all is well. thanks again for all input
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| tedious |
Posted on 07/19/13 - 8:17 AM
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Certainly a busted plug could be a factor, but I would have thought that would give you trouble at all RPMs.
Props are characterized by diameter and pitch and model - usually there is a number somewhere on the prop that will let you look up what you have.
Your consideration that the prop is OK because the boat gets on a plane very well is not completely correct as acceleration is only 1/2 the equation. If you are underpropped (too low a pitch) it is like driving a car in too low a gear - you'll accelerate very well at low speed, but you'll hit maximum RPM very fast. That is my concern about your setup.
In any case, changing one thing at a time (the broken plug) and retesting is the right approach. Good luck!
Tim
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| rjstox1 |
Posted on 07/21/13 - 3:35 PM
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Sunday ride up the Piscataqua Maine/NH border......Full moon tide made it a nail biter so we headed for calmer waters.......Hit something below the water line in about 40' of water.......bent prop the outcome......must have been a log in some of the seaweed floating on the surface.......question....3 blade or 4 blade replacement?
Edited by rjstox1 on 07/23/13 - 4:52 PM |
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| rjstox1 |
Posted on 07/24/13 - 6:56 PM
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tedious wrote:
RJ, did you just leave on the same prop that was used when the motor was on the pontoon boat? I am sure a 'toon would not go as fast as your 15, so if you just reused it, that may well be your problem. In any event, you'll want a tach on there to help you figure out the correct prop.
Tim
The prop I have is a 11 3/4 X 10 ........just before the rev limiter starts to engage, I am going 23.5 mph with a full load. A tach is to be installed by the weekend so I can be more specific regarding the rpm vs. speed. Thanks for you help
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| tedious |
Posted on 07/25/13 - 5:28 AM
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Been there, done that with a submerged object - not a lot you can do about it. I was out that night myself a bit north of you - beautiful full moon. I guess the good news is you needed a prop anyway!
The other piece of good news is that you don't have a motor problem - you're hitting the rev limiter for sure. Using the 2.08 to 1 gear ratio and the 10 pitch prop, and assuming 8% slip, it calculates out to 25 mph at 6000 RPM. It looks like you need about a 13 pitch prop, and that is what I would try next - should get you into the 33 - 34 MPH range. Get a nice stainless prop while you're at it - no sense handicapping your nice ride with older technology and the stainless ones are not that much more expensive at an online discount place, although they are at the dealer. I have had good luck with Stiletto props from Dan's Discount Props, although I am unsure of the exact fitment. The Star 1 in 12x13 might be the ticket, looks like the price on it is $205 with the hubkit.
I don't see any reason to put a 4-blade prop on a relatively light boat like a 15 unless you're always running with a very heavy load.
Tim
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| Phil T |
Posted on 07/25/13 - 6:47 AM
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Tim has some very good advice.
Going forward, it is important to tell us what model you have (classic 15)
We should know at what height your motor is mounted? Looking at the top set of holes, how many empty bolt holes are above the bolt?
To accurately setup your engine/prop, we need to know what your typical load/passenger count will be. Your load factor will affect the brand/size of propeller recommended.
You should find a marina or shop that will let you test props before buying to save you from a $200 mistake.
As it has been said, dealers do not always know best when it comes to to engine height and props for Boston Whalers. Members on this board have proven results from actual use and testing.
Edited by Phil T on 07/25/13 - 6:48 AM |
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| rjstox1 |
Posted on 07/25/13 - 10:23 PM
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Phil T wrote:
Tim has some very good advice.
Going forward, it is important to tell us what model you have (classic 15)
We should know at what height your motor is mounted? Looking at the top set of holes, how many empty bolt holes are above the bolt?
To accurately setup your engine/prop, we need to know what your typical load/passenger count will be. Your load factor will affect the brand/size of propeller recommended.
You should find a marina or shop that will let you test props before buying to save you from a $200 mistake.
As it has been said, dealers do not always know best when it comes to to engine height and props for Boston Whalers. Members on this board have proven results from actual use and testing.
Phil and Tim,
I have the 1984 15' Sport. There are NO empty holes above the bolt as the engine is all the way down to the top of the transum where the first bolt is in the top hole. Average weight of all onboard with gear is about 425-450 lbs. Thats two of us with gear and gas. We do have the occasional extra couple of passengers on board which would kick that up to about 650 lbs. Honda Tach installed yesterday as per the wiring diagram but did not work properly. It is getting power and pegs when I start the engine. I will adjust the pole setting today and try again. I have been considering an SS prop and the prices aren't so bad as to be prohibitive. The 12 X 13 prop sounds like the option to try. Hope this information helps. Let me know what you think about the engine height. Thanks for all input.
Edited by rjstox1 on 07/25/13 - 10:24 PM |
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| tedious |
Posted on 07/26/13 - 5:08 AM
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RJ, if you go with a good stainless prop, you'll be able to (and should) move the motor up two holes. That is, raise it until there are two empty holes above the hole the bolts are in. This should leave your antiventilation plate around 3/4" above the keel, which is about where you want it. I know you had your transom rebuilt, so that may not be perfect but it is a good place to start.
The advantage of raising the motor is that it will give you slightly better mileage and top speed, create less bow rise on accelleration, and make trim changes more effective.
It's pretty easy to raise the motor - loosen the bottom bolts slightly, remove the top ones, and lift the motor. Let the bottom bolts slide up in the slot. and reinsert the top bolts when they line up with the holes you want. It's best done as a two man job unless you have something like a chainlift. You can lift the motor with a floor jack, or even just put a block of wood under the skeg and raise the trailer jack to lower the stern relative to the motor.
Tim
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| rjstox1 |
Posted on 07/26/13 - 5:31 AM
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Tim,
The motor looked a "little" low to me from the beginning. I will get the tape measure out and eyeball where the 3/4" mark should be and see what hole I need to raise the motor up to. If the motor is raised, does that mean a smaller diameter prop is necessary? This is my first boat and the learning curve regarding engine set up is pretty big. I can see the importance of having a marina work on your boat that knows what they are doing. It appears that the marina where I bought the used engine just set it on the transum and bolted it down. Knowing the the antiventilation plate should be around the 3/4" mark, I will get on that today. Thanks again Tim
Edited by rjstox1 on 07/26/13 - 5:32 AM |
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| tedious |
Posted on 07/26/13 - 5:41 AM
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rjstox1 wrote:
If the motor is raised, does that mean a smaller diameter prop is necessary?
I guess theoretically if you raised the motor enough, you might need a smaller prop to keep it in the water, but in practice, no. Modern props have a much better grip on the water, so they can run closer to the surface, improving performance. Many dealears and boatyards have not figured this out yet - or maybe it's just the consequences of mounting a motor too low are less obvious than the consequences of mounting too high, so they minimize customer complaints by slamming the motor all the way down on the transom. Performance suffers, but not everyone would notice that.
In any event, you only have to set the height once, so it makes sense to get it right.
Tim
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| rjstox1 |
Posted on 07/26/13 - 12:41 PM
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tedious wrote:
rjstox1 wrote:
If the motor is raised, does that mean a smaller diameter prop is necessary?
I guess theoretically if you raised the motor enough, you might need a smaller prop to keep it in the water, but in practice, no. Modern props have a much better grip on the water, so they can run closer to the surface, improving performance. Many dealears and boatyards have not figured this out yet - or maybe it's just the consequences of mounting a motor too low are less obvious than the consequences of mounting too high, so they minimize customer complaints by slamming the motor all the way down on the transom. Performance suffers, but not everyone would notice that.
In any event, you only have to set the height once, so it makes sense to get it right.
Tim
Tim....I just looked at your home page.....great looking whaler.....hope to get mine looking half as good as yours this winter.
I took some pics and posted them on my home page. The engine IS low and should be raised at least an inch as indicated in the pic, however, the transum design did not allow for the lower bolts to be set in the bottom elongated slot on the bracket. That elongated slot is so low on the engine bracket that I would have drilled into a void in the lower inside transum area and it would not have been possible to get a nut on the bolt end. This prevents me from raising the engine. The pics show both the inside and outside of the transum where the bolts have been placed. I do not know if there is a way to resolve this problem. I guess I could buy one of the adjustable brackets for the transum and then attach the engine but that may not be worthwhile. I may just have to suck it up and live with less performance due to the problems encountered. If we can't come up with a reasonable resolution, I think I will get the 12 x 13 SS prop and enjoy the rest of the summer. Any other thoughts or recommendations are appreciated. Thanks again for everyones suggestions.
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