Yamaha T50TLR on 18x60 weldbilt low power

[mcdowellkm]

I know i have never posted here before, but here is my problem. I am a diesel technician so i'm pretty handy with these sort of things usually, but this one has me a little taken back. first lets go through a little history.

Bought my 2003 WeldBilt 18x60 flat bottom boat 2 years ago for a duck/river boat. It has a 2001 Yamaha T50TLR High Thrust tiller on it. When i purchased the unit it had sat for 3 years un-used. Fuel tank was full of nasty stuff so i took it out cleaned with solvent and also replaced the fuel line from the bow of the boat where the tank is all the way back to the motor. Carbs were also full of trash so i took them off, cleaned all 4 of them in untrasonic as well as pulling the jets (both idle and main), as well as the emulsion tubes and throughly cleaned them at the same time. Boat would then (once started) run like a sowing machine. Had a problem with it being hard to start. Would make about 1 revolution then would act like it had a dead battery (or an old chevy with headers causing heat soak in the starter). Fixed this problem by adjusting the valves (which with all the paint that was still on the bolt heads told me had never been done). Now she starts and runs very smooth with no question as to reliability.

Problem is this boat is very slow to plane, as well as when i have it really loaded down (4 guys, guns, dog, decoys) , then it barely gets on plane. when going lighter weight (fishing in summer 2 guys fishing gear) it still takes a while to jump on plane. When loading onto the trailer it's like it doesn't have enough guts to shove itself onto the trailer (which i have never seen a boat that weak). (My dad's 17' lowe jon boat with a 35 merc 2-stroke has no trouble with torque while loading or getting on plane with same loadout as my boat by the way.) First crack of the throttle is real strong but then it falls on it's face almost like it's not advancing the timing correctly But timing is non adjustable on the Yamaha right?. prop is a 13p vengance and the anti-cav plate is 1/2" below the bottom of the boat. also when crusing at wot (i know i don't have a tach on it yet) just seems to me like it's no where near the ideal rpm range at wot. I honestly chucked this up for a long time to this being my first 4-stroke and it being so quiet.

Second problem. This boat will porpoise real bad anywhere above trim all the way down. I have tried moving people to the front and it doesnt really seam to help. I have an 18gal cell mounted in the bow as well as boat has a full 5' deck and 70lb thrust trolling motor mounted on the bow so i would assume there is enough weight up there. I can put people, cooler, decoys in the front and it still wants to bow bounce (porpoise) anytime im higher than trimmed all the way down. in the back i just have 3 batteries (one for outboard, 2 for trolling motor) and myself (250lbs), a tool box in one of the two lockers in the back, and an anchor in the other locker and thats it. Boat originally had a StingRay whale tail on it when i bought it but i noticed it really fought me for steering and caused magor drag on the boat due to the cav plate being lower that the bottom of the boat, plus when i ran it i still had the same plane and low power problems.

Any help or sidection on this would be greatly appreciated.

I have done a compression check which was good, also i only run 93 octane in all my boats with seafoam in them also. another thing i have done is add in an inline fuel filter before it gets to the engine.

 

[hotshotinn]

drop down couple of pitch on your prop and you will come out of the hole better.sounds like you are trying to haul big heavy loads with just 25 horse.you can allso play around with your engin height too for best performance but you can only get so much out of the smaller engins

 

[rscottp]

I don't know much about motors(you do obviously) but going down on prop pitch is probably a good idea. Is it possible the floatation foam is waterlogged making the boat much heavier than it should be?

 

[mcdowellkm]

The boat has a 50 horse "high Thrust" (which basically means it uses a 2.33:1 instead of a 1.88:1 final gear in the lower unit) and i run a 13p prop so i would have thought it would have enough...I'm gonna throw a tach on it this weekend and see what it's actually putting out. Better to know for sure instead of guessing by feel and sound i suppose. I'll play with some different props but i just really thought it could have been more of a motor problem.

Suppose i should add in this is deamed a commercial vessel so it has no floatation foam in it.

 

[huntinfool]

I have an 1860 tracker grizzly and it is rated for a 90 HP. My boat will get on plane, but only run wot at 33mph.
My initial thoughts are you are over weight/under powered. For the amount of weight I think you have too little motor. 4 guys ( 200 lbs average) 18 gal. fuel, 3 batteries, trolling motor, duck decoys, guns, shells, etc. A different pitch prop might help, might.
I'd also consider raising your outboard up one hole. This might help both problems. Or you could add a whale tail to help with the porpoising.
If it were mine, I believe I would raise the motor one hole and see how it acts first. This is easy and free. If this helps the porpoise issue then no need for the fin. Lastly would be the prop. But I think even with a different prop, you're still overweight and under powered.

JMHO.

 

[Zum]

Yamaha's outboard website's preformance bulletin for the G3 1860 cc w F50 shows 11 5/8X 11pitch, 30mph @ 5950. Check it out. Oh, it also says 3.74 sec. to plane.
Although you have the high thrust one,it might handle the bigger prop....but only if lightly loaded.The tach is going to help you alot with props.
Porpoising...I'd raise the outboard also, just make sure it pumps a good flow of water.

 

[juggernot]

Zum » Today, 20:18[/url]"]Yamaha's outboard website's preformance bulletin for the G3 1860 cc w F50 shows 11 5/8X 11pitch, 30mph @ 5950. Check it out. Oh, it also says 3.74 sec. to plane.
Although you have the high thrust one,it might handle the bigger prop....but only if lightly loaded.The tach is going to help you alot with props.
Porpoising...I'd raise the outboard also, just make sure it pumps a good flow of water.

I have a G3 1860, it is not a flat bottomed boat, it's a semi V hull, 5 degrees I think . I'm no expert but I think your overloading your flat bottomed boat and have trouble staying on plane (porpoising) and pushing water w the bow instead of riding on top of it. Have you checked the weight capacity of your hull to the weight you are carrying? I would suggest a 4 blade alum. prop for that 50 HT. A 4 blade improved my boats performance all around from the factory alum 3 blade. I also agree w raising the motor till the AC plate is level or slightly above the keel.

 

[mcdowellkm]

Thanks for the advice guys.

I have to travel out of town next week but hopefully will be able to raise motor and retest this friday before i leave. Come to think of it i do notice alot of splash up from the cav plate while on plane.

The boat is rated for up to a 115HP motor, and i'm not sure what the capacity is on the vessel itself as it has no coast guard tag on it with being a commercial deamed vessel (also why it has no flotation foam).

I called the dealer who sold the rig new to the guy i bought it off of and bounced this problem onto him. He suggested putting floatation pods on the boat. Says i have way to much stern weight. He also is trying to get me to upgrade the outboard to a 90hp but i just dont have the funds for that right now. He claims that if i throw the pods on it will counteract all the battery weight and the weight of the heavy 4-stroke, not to mention the guys i normally hunt and fish with are equal size to me ~250lbs.

I will update as soon as i raise the motor.

 

[juggernot]

After researching/viewing Weldbuilts 1860 I'm wondering if the corrugated bottom w 15 slots causes some drag and reduces top speed? I could not find any capacity or max. HP info.

 

[juggernot]

I think your "dealer" is full of it w the pods recommendation, you could move the batteries forward pretty cheap if that's the problem. If you're runnin a 50 and rated for 115 and loaded near capacity you're under powered IMO. My 03 F-90 weighs 380lbs !. I also have a 12 gal. tank and 2 batts right on the stern, she has a fat a$$ !!. I'm sure the 50 is much lighter than the F-90 and my 1860 will run 40+ and over rev w a 17 pitch 4 bld. prop. I'm no expert but I thought the High thrusts were low geared for propelling large, heavy, slow craft like big pontoons or used for large sailboat kickers? I think you might need a standard 2 or 4 stroke 90 or higher HP outboard for more speed with the loads you're carrying but again....I'm no expert. I checked again and the HT motors have a different lower unit and propeller design than the standard 4 strokes and are apparently not built for speed.

 

[mcdowellkm]

Is there any way to bump the horse power in the boat. I was looking at the specs for the 60 and the 50 from yamaha and they share the exact same compression, bore and stroke. That only leaves the cam and carbs...Didn't know if it would be possible to hop-up the ponies in my little 50?

 

[juggernot]

I think it's not the HP, it's the gear ratio and propellers designed to push heavy hulls/loads that will never plane. Look at Yamahas website at the difference in the High thrust and standard outboards lower units and props in the same hp range as the high thrust engines, they are very different the HT props have no rake at all and round blades.

 

[mcdowellkm]

one more question i have and i know this sounds crazy but hear me out. Last fall during duck season i was driving the boat and thought something was wrong because it was big time losing power. turns out with my waders i couldnt even feel that i was stepping on the fuel line. Reason i bring this up is that the boat never died or missed, but it was just low on output power. Now i know i told you guys earlier that i had installed an inline fuel filter onto this thing and it's one of those 5/16 30micron units you get from the boat dealer but hear is my question. My fuel cell is mounted all the way in the front of the boat. on left hand side under the deck. The line runs through the right hand side wall, then at the stern has the primer ball, then the inline fuel filter, after that it goes through the factory fuel filter on the outboard then to the fuel pump. So we have literally like 20' of fuel line, a pick-up tube in the cell, 2 fuel filters to go through, then it makes it to the pump. Do you think with it having so much distance to pull the fuel that it could be short on supply volume? is this possible? Also i am not sure the difference it would make especially at WOT but i have never synced the carbs since i have owned it.

I am really over thinking this.

I will buy a tach friday, raise the motor, and see where that gets me.

 

[mcdowellkm]

Prop thing is driving me crazy so i went out and took some pics of what is on the boat now. It's a 10 1/2" x 13p SS Vengeance 3-blade.

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[mcdowellkm]

AH HAH!!

So being as how i can't let things go at all. i started looking into props...Turns out the T50TLR Yamaha High Thrust that has the 2.33 gear ratio is supposed to use a 15 spline 14-15"dia prop. I thought this was rather funny due to the fact that when i looked up the part number for what i have on the boat now it stated 13 spline 10.5"dia. Just to be sure i went out to the boat and popped off the prop and counted the splines...Sure enough what i had only had 13 splines. so since curiosity was killing me at this point i decided to throw a wrench up on the ole flywheel bolt, throw her in gear and give her the ole redneck gear ratio check. I was rather baffled to find that 1 full revolution of the prop only yielded me a shade over 1 3/4 turns from the crank. So either the guy who sold it to me lied by saying he never had the lower unit off or someone at the factory 13 years ago put an F50TLR lower unit on this boat. Kinda strange the model number on the tilt/trim mount says T50TLR and the cowl cover says high thrust on it, but oh well i guess.

So my previous thinking was that the T50 with the lower ratio turning a 13" prop would be like the F50 higher ratio turning an 11.5" prop. Now that i know what i know, the performance bulletins make a whole lot more since. When you look at those boats performance reviews that are set up similar to mine and now with the correct gear ratio i know i am def 2" over propped for my weight load-out. So now i guess we put the right prop on the boat, raise the motor, and get a tach? Right?

 

[turbotodd]

Raise the motor. About 1/2 to 1" above is going to be close. Could go more if the prop has some cupping.

IF you have an F50 with the 1.88 foot, 11" pitch is about all that heavy boat is going to take. Maybe even drop to a 10" with a heavy load. And here's why I think that. The boat is rated for 115. You have a heavy 50 on it. It will be a slug. BUT it is what you have (and that F50 is a sweet motor, BTW) and if you can maximize what you have to deal with, it'll be more enjoyable to run. Just don't expect it to be a powerhouse.

Synching the carbs helps a bunch of these, as well as any of the four stroke multi-carb engines. Did an F50 recently, guy was a friend of mine and didnt want to wait to sync the carbs. Back the next day says it's idling rougher than he thought. I drilled the caps off of the idle mixture screws. Hooked up a manometer. Synched all 4 to within .5 in/Hg, then adjusted the mixture screws. It literally is so quiet and smooth that the only thing I hear with it running is the pee water hitting the lake. Guy runs it across the water and comes back saying it's a different motor. No speed or torque increase but it holds plane lower and runs a LOT smoother, with seemingly less throttle input to maintain speeds. This same friend swears up and down that his 15" prop is THE prop for his motor. So I "borrowed" his boat while he was at the bar and put an 11" on it that I had in the shop (and wasn't using). The difference was night & day. Top speed even increased by about .5 mph. On plane a LOT faster. Max RPM went from 4600 to 5950 (with just me in it, plus a couple fishing rods and a 30 lb tackle box). I left it on there and put the 15" in his box for a spare prop.

Also on the carbs, these 50's are REAL sensitive to carbs...keep in mind the jetting is different for each cylinder, and swapping them without knowing can affect the power output. Years ago I was helping a customer who had let his F50TLR sit for a few years, plugged the carbs, and asked me to clean it all out & get it going for him. Sure no problem. Pulled the carb set, disassembled, dunked it all in the ultrasonic and pulled 'em out looking brand new. Screwed the jets back in and it ran. Customer picked it up and called while on the lake, said it didn't sound quite right. Bought it back, I found nothing wrong. It ran well in the tank. This went on for several weeks, I was into EVERYTHING (valves, cam timing, ignition timing checks, etc). Then the Yamaha rep was by the shop..for his once-every 2 years visit, and asked me to check YDS for the jet sizing. Sure enough, different size main jets and I think 3 different pilot jets (but I don't remember for sure on the pilots). Swapped it all around like it should have been and it honestly sounded differently, idled different, and revved cleaner. Customer gets it back and calls to say it was absolutely perfect. Thank GOD. Lot of lost shop time.

Always remember on the 4 stroke stuff that they are a LOT more sensitive to propping. The wrong prop KILLS them, the smaller the motor the more sensitive they are. With the old 2 stroke stuff you could get it close and you were happy. Close doesn't cut it with 4 stroke engines, well most of 'em. The variable cam timing stuff is changing that a little....