2020 Tohatsu 50 Bad performance, Is It My Prop?

kirkkoh

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Hello everyone, im a new member and have learned so much from this site that i decided to seek yalls help! Long Post but i'd appreciate the help!

I have a 1996 tracker PT175 with a 2020 Tohatsu 50 4 stroke 20" shaft (209 lbs). With calm water, no wind, a light load, and just me top speed is 31mph per GPS. i have my outboard anti-cavitation plate either flush or slightly above the bottom of the transom which is the 2nd highest mounting hole. No noticeable cavitation/ventilation when going straight forward. Water pressure seems consistent and strong, but i will be installing a gauge.im running a stock tohatsu 11x15 aluminum 3 blade prop, however it has a nickel/quarter sized "notch" on the very edge of one of the blades, i know this isnt good. I just got the motor and haven't installed my RPM Gauge yet. I know there's atleast another 3-5 mph that can be gained on this boat.

MY ISSUES: When i trim to max allowed, the motor looks even and the lower unit looks like its sitting in the water where it should be and everything is fine except... i blow out in turns, not even sharp turns also i get some bow rise but not much at all, nothing like i did with my merc 75 4 blade. i assume its a prop issue and not a motor mount height issue.

My idea is to install the rpm gauge and get max rpms and talk with powertech and get a dialed in SS prop. My goal is to fix the blow out issue aswell as maximize speed with the right prop. i also considered getting a micro hydraulic jackplate maybe with setback? but trackers are known to be stern heavy and i cant find much helpful info online of any before and after results or if its even do-able.
 

kirkkoh

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kirkkoh said:
Hello everyone, im a new member and have learned so much from this site that i decided to seek yalls help! Long Post but i'd appreciate the help!

I have a 1996 tracker PT175 with a 2020 Tohatsu 50 4 stroke 20" shaft (209 lbs). With calm water, no wind, a light load, and just me top speed is 31mph per GPS. i have my outboard anti-cavitation plate either flush or slightly above the bottom of the transom which is the 2nd highest mounting hole. No noticeable cavitation/ventilation when going straight forward. Water pressure seems consistent and strong, but i will be installing a gauge.im running a stock tohatsu 11x15 aluminum 3 blade prop, however it has a nickel/quarter sized "notch" on the very edge of one of the blades, i know this isnt good. I just got the motor and haven't installed my RPM Gauge yet. I know there's atleast another 3-5 mph that can be gained on this boat.

MY ISSUES: When i trim to max allowed, the motor looks even and the lower unit looks like its sitting in the water where it should be and everything is fine except... i blow out in turns, not even sharp turns also i get some bow rise but not much at all, nothing like i did with my merc 75 4 blade. i assume its a prop issue and not a motor mount height issue.

My idea is to install the rpm gauge and get max rpms and talk with powertech and get a dialed in SS prop. My goal is to fix the blow out issue aswell as maximize speed with the right prop. i also considered getting a micro hydraulic jackplate maybe with setback? but trackers are known to be stern heavy and i cant find much helpful info online of any before and after results or if its even do-able.
 

MrGiggles

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The prop isn't helping things for sure. But I think that motor is performing pretty well as-is. 50hp is not much on a 17' boat.

Usually blowing out on turns indicates that the motor is too high. You can try dropping it down some, or having some cup added to the prop. A four blade can help as well.

I certainly understanding wanting to get the most out of your setup, but you will reach the point of diminishing returns very quickly, especially when you start talking about hydraulic jack plates and stainless props. My opinion, get a decent 3 blade aluminum that puts your RPMs about where they should be, set the motor to where ventilation is minimal, and spend the money on things that actually catch fish.
 

kirkkoh

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I know 50hp is underpowered for sure. But these new tohatsus have everyone impressed with there power and not only that but it’s only 209lbs. I would think 31 would be normal with wind or chop with another person on board but not an empty hull with just me on calm water. And i think you’re right. Too much money to gain a couple horses isn’t worth it. I think I’ll just go with a SS PROP and call it a day
 

DaleH

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MrGiggles said:
Usually blowing out on turns indicates that the motor is too high.
Agreed that prop is not helping ...

I set the OB height by having the vent plate at the surface of the water or just being splashed ... too deep robs performance. However, you WILL need to trim the OB "in" when cutting sharp turns!

That is why most Dealers mount or rig the new OBs WAY TOO freakin' DEEP! To avoid callbacks from Customers ...
 

nowgrn4

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I would start considering a new prop, and I would highly recommend getting a tach before you do to help choose the right size.
I could definitely see how that "Compromised" blade contributes to your ventilation issue in turns.
 

sonny.barile

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I went through this with my Duranautic 16 side console and Evinrude e-tec 30 hp. I didn’t have a Tach so I was unsure of rpm. My boat hit about 22 with just me and about 19 with a passenger aboard. After adding a tack I found I was getting only 5400 RPM’s. The suggested range is 5500 to 5800. Did some research about motor heigh. The cavitation plate on a boat without much deadrise in the transom needs to be at the waters surface when planing. If not it will cause drag. If it’s to far above it will blow out without much trim.

After the height was set correctly on my boat (had to be raised) I went to 5700 rpm’s with just me in the boat and hit over 28 mph. With another person aboard I get 5600 rpm’s at 26mph. Ended up keeping the prop I had.

Your prop is badly damaged and is going to vibrate at high revs so it’s going to make it harder to work with when trying to figure it out. I would by a cheap Solas aluminum that matches your specs for now and then add the Tach. Motor height may be the only adjustment you need.

Some things to know……
If you want more speed you need to go up in pitch but it sacrifices rpm.
If you want more rpm you will need to go lower pitch and will sacrifice speed.
Stainless props are stronger, have less efficiency loss because they don’t flex, and have more cup than aluminum so they don’t blow out, but if you hit something……all the force goes into your lower unit. I would rather replace damaged aluminum props instead of damaged lower units.
If you are not in the suggested range you do not get all of the rated horsepower.

I would shoot for a pitch that gives you the middle of the rpm range and that will get you good speed. My guess is you should be hitting about 35 mph if dialed in just right.

Sorry if this is a lot of info…..but because I went through this recently it’s fresh on my mind.
 
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kirkkoh

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I went through this with my Duranautic 16 side console and Evinrude e-tec 30 hp. I didn’t have a Tach so I was unsure of rpm. My boat hit about 22 with just me and about 19 with a passenger aboard. After adding a tack I found I was getting only 5400 RPM’s. The suggested range is 5500 to 5800. Did some research about motor heigh. The cavitation plate on a boat without much deadrise in the transom needs to be at the waters surface when planing. If not it will cause drag. If it’s to far above it will blow out without much trim.

After the height was set correctly on my boat (had to be raised) I went to 5700 rpm’s with just me in the boat and hit over 28 mph. With another person aboard I get 5600 rpm’s at 26mph. Ended up keeping the prop I had.

Your prop is badly damaged and is going to vibrate at high revs so it’s going to make it harder to work with when trying to figure it out. I would by a cheap Solas aluminum that matches your specs for now and then add the Tach. Motor height may be the only adjustment you need.

Some things to know……
If you want more speed you need to go up in pitch but it sacrifices rpm.
If you want more rpm you will need to go lower pitch and will sacrifice speed.
Stainless props are stronger, have less efficiency loss because they don’t flex, and have more cup than aluminum so they don’t blow out, but if you hit something……all the force goes into your lower unit. I would rather replace damaged aluminum props instead of damaged lower units.
If you are not in the suggested range you do not get all of the rated horsepower.

I would shoot for a pitch that gives you the middle of the rpm range and that will get you good speed. My guess is you should be hitting about 35 mph if dialed in just right.

Sorry if this is a lot of info…..but because I went through this recently it’s fresh on my mind.
 

kirkkoh

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Thanks, So i shouldnt throw a tach on and use those rpm readings? what you said caught my attention... so the RPM readings with my damaged prop would be inaccurate in helping determin my next NEW prop? i'd hate to have to buy a new prop just to get accurate rpms to go buy ANOTHER prop lol.
 

sonny.barile

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Thanks, So i shouldnt throw a tach on and use those rpm readings? what you said caught my attention... so the RPM readings with my damaged prop would be inaccurate in helping determin my next NEW prop? i'd hate to have to buy a new prop just to get accurate rpms to go buy ANOTHER prop lol.
To be honest I couldn’t tell you……without witnessing it. My intention is not to steer you into any plan but to make you aware of what you most likely are up against.

If it were me I would start with a cheap tach like the “Tiny Tach“. You can pick one up for about $20 on Amazon. The installation is simple. You just wrap the sensor wire around the outside of a sparkplug wire. There is no power or wiring involved……very simple and accurate. You can read your rpm’s at full throttle trimmed out and see where you are at, then work from there….A tach is never a waste. It’s great for finding the sweet spot when underway and can be your first indicator of outboard issues.

Is your motor a tiller or console?
 
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airshot

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Definetly need a tach or your guessing. Prop needs to be in good shape or your guessing. If you want the absolute best performance you need a power trim !! I have a 16' side console alum Sylvan, I have 3 heavy group 31 batteries and a group 24 starting battery. I have a 40 hp Merc 40hp 2 stroke. Typically get 27-28 mph, but if I get the trim just right I can get 31 plus mph ....so being able to fine tune that trim makes a big difference along with no nicks on the prop !!
 

kirkkoh

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To be honest I couldn’t tell you……without witnessing it. My intention is not to steer you into any plan but to make you aware of what you most likely are up against.

If it were me I would start with a cheap tach like the “Tiny Tach“. You can pick one up for about $20 on Amazon. The installation is simple. You just wrap the sensor wire around the outside of a sparkplug wire. There is no power or wiring involved……very simple and accurate. You can read your rpm’s at full throttle trimmed out and see where you are at, then work from there….A tach is never a waste. It’s great for finding the sweet spot when underway and can be your first indicator of outboard issues.

Is your motor a tiller or console?
it is a console. and i bought and installed one of those tachs but wasnt aware the one i bought doesnt have a preset program for a 4 stroke 3 cylinder.
 

kirkkoh

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Definetly need a tach or your guessing. Prop needs to be in good shape or your guessing. If you want the absolute best performance you need a power trim !! I have a 16' side console alum Sylvan, I have 3 heavy group 31 batteries and a group 24 starting battery. I have a 40 hp Merc 40hp 2 stroke. Typically get 27-28 mph, but if I get the trim just right I can get 31 plus mph ....so being able to fine tune that trim makes a big difference along with no nicks on the prop !!
okay that gives some clarification then. i just installed a spark plug wire digital tach but didnt realize it didnt have a preloaded program for a 4 stroke 3 cylinder, ill get one that does. ill buy a cheap aluminum prop with same diameter & pitch as ive got now on ebay for $88 and then do a WOT RPM test to get the info i need. I'll then head over to powertech and hear their recommendations. Also i do have power trim? what makes you think i dont? unless youre meaning a jackplate...
 

airshot

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A jack plate can make a difference but not enough to justify the cost on a smaller motor. Didnt know if tou had a power trim or not, but needed to throw that in as you are looking for peak performance. With your vent plate parallel to bottom of the boat, that vent plate should be even or slightly above the boat bottom. With a good prop and a tach, you should be good to go. I have mine set up to run about 100 rpm above max rpm with just me in it. I never run wot for long periods of time anyway. With that set up, I only loose about 1 or 2 mph with a passenger an extra fishing gear
 

FuzzyGrub

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okay that gives some clarification then. i just installed a spark plug wire digital tach but didnt realize it didnt have a preloaded program for a 4 stroke 3 cylinder, ill get one that does.
The ones I've used have settings for "spark per revolution", not based on number of cylinders. The wire only attaches to a single spark plug.
 

VinTin

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okay that gives some clarification then. i just installed a spark plug wire digital tach but didnt realize it didnt have a preloaded program for a 4 stroke 3 cylinder, ill get one that does. ill buy a cheap aluminum prop with same diameter & pitch as ive got now on ebay for $88 and then do a WOT RPM test to get the info i need. I'll then head over to powertech and hear their recommendations. Also i do have power trim? what makes you think i dont? unless youre meaning a jackplate...

The tach only needs a 4 stroke setting. It doesn't matter the number of cylinders as it is only counting the 'sparks' on one cylinder.
 

kirkkoh

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The ones I've used have settings for "spark per revolution", not based on number of cylinders. The wire only attaches to a single spark plug.
Yes i know it only goes to one plug. The one i bought comes pre loaded for certain outboards that you can choose from for your specific application. I know the modes were mainly 2/4 stroke with 1-2 cylinders. I have a 4 stroke 3 cylinder
 

thill

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IF you have Amazon prime, you can buy a couple of props, and return one or all of them if they don't work, as long as you don't damage them. That way, you don't get stuck with one that isn't suitable.
 
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