Thanks for watching, I'm happy to help!

Thank you so much for the kind words!!

That’s what I was going for, glad it helped!

She’s got lots of great points…especially regarding cavitation.

Thanks! Hoping it'll help some folks get their boat dialed in.

Thanks for watching!

Happy to Help!!!

Thanks so much!!

Thank you for watching!

Happy to help, thanks for watching!

Thank you! Hoping it helps some folks out who aren’t sure where to start.

Great questions! It seems to be that a little chewing on the ends of the props doesn't change things terribly, but then a little more damage and you may start to see some speed loss, slippage, and abnormal vibration. On a pontoon boat the speed loss may not be noticeable until there's significant damage compared to a planing style hull. I find that three blade stainless props will yield best top speed. They allow for larger diameters and each blade can have a bit more cup to them. Obviously, there will be others out there who swear by four blade...so I'm thinking this is a "to each their own" scenario, and different hull/motor combos might react differently too. Four blade props should do best for grabbing water at the dock for fine tune handling, reversing, etc. If there's anything more significant than what I can touch up with a hand file then I would say it's time to have it restored. Things can get out of balance if you try to fix majorly damaged blades. I think the biggest signal that it's time to have it restored or replaced is when you're feeling the abnormal vibrations or shaking at certain (or all) RPMs. When I knocked most of a blade off on the river a couple years ago the boat would run slower but ok at certain RPMs. A little higher or a little lower than that sweet spot and it felt like the whole boat was going to shake apart! We got home ok, but had to swap that prop out right away!

Your porpoising (bouncing of the bow) has more to do with needing more weight up front OR more negative trim (or both). Make sure your motor’s trim is adjusted to be able to go all the way down so that you’re getting as much negative trim as possible to help get the bow down. Sometimes there’s a bolt or a pull pin that allows more negative trim. Worst case you can install negative wedges between the motor and boat that will give more negative trim.

I have the same set up with a 10 1/2 inch 14 pitch prop and it does good.

A 4 blade prop will tend to lift the stern somewhat, thus may help. Try to borrow one for testing. It's very important your engine can operate to it's maximum rpm, thus a known calibrated tachometer should be used. One big cause of porposing is a hull with too much rocker shape, weight in the front to bring the bow down will probably help as well.

Glad you got a kick out of that!!

Good, glad you found my channel. I have a few gauge install videos for different brands. I primarily use Faria Gauges as I've found them to be the most universal and user-friendly with outboards. Check out my playlists for electrical stuff and engine rigging.

The owners manual will tell you what your operating range of RPMs should be at wide open throttle, but will not give you any guidance to prop diameter and pitch. That will have to come through testing with a tachometer.

I refer to this chart for all of my WOT numbers: www.kirschbaum.at/ki_prop/pdf/2015/RPM%20Chart.pdf It looks like you're correct, according to the chart an older 1980s vintage Johnson/Evinrude 2 cycle should run somewhere between 5500 and 6500 RPM.

Thank you for the reply. I appreciate it.

@@doctordifferentialspeedsho9506happy to help!

Glad you found us now though!! There’s always the option to build another out of an old pontoon!!!

You'll get cavitation or ventilation from two things typically...the motor being mounted too high on the transom OR a disturbance of water flowing to the propeller. The first has an obvious fix...lower the motor until the cavitation stops. The second is a little trickier because every boat is different. In my observance, some pontoons just weren't designed with high HP motors installed. So if they ran ok out of the factory with a 25hp or 40hp then they kept making them that way. When higher speeds are reached with higher hp the flow of water changes and can cause issues with how it feeds the motor. Again, lowering the motor would be the first way to fix it. Other things that can help with it are hydrofoils (aka whale tale) on the motor to help smooth the flow of water feeding the prop. Also, moving the entire transom back can help as well. The flow of water off the pontoons (standard pontoon, not tritoon) is very interesting to watch at higher speeds. The water will sort of flow down off of the pontoons just forward of the backs of the toons...if the motor is tucked up in front of the outer toons that flow down will make the better flow of water go "under" the prop. Water will always rise back up after being displaced by a hull, so moving the motor back a couple feet can help with that. Lots of variables here, but usually step one is lower the motor if that's possible!

thank you so much my motor is all the way down would you cut the transom down or move it back thanks again @@tomspontoons

@@tomspontoons i forgot too add that I'm not able to trim the motor up at all it will just cavitation /ventilation thanks again for your help hope you all have a great weekend!!!

@@ronaldsmith4068 That's a tricky one! Lowering the motor should eventually take care of the issue. I would probably lean towards that instead of moving the transom back, unless you're tearing the boat down to restore at the same time. Crest doesn't allow for access to the transom bolts from the underside...Their crossmembers only give access when the deck is removed.

@@tomspontoons thanks again I really appreciate it

No, it really should not have any impact as there is little to no resistance to the motor/boat from the air. It's the load from the motor pushing the boat through water with a load that impacts the RPMs the most.

That does seem like a low pitch for that motor and boat combination. That motor should run up to around 5,800 to 6,000 RPM at wide open throttle with a light load. I would expect to see 25 mph out of that boat. I'd start by going up to a 13" pitch which should drop the RPMs a little bit and might give you better bite. Your 11" might be so flat of a pitch that it's having slipping issues. Really hard to say without being there to see and hear everything happening, but I'd start by going up in pitch a couple inches to where you can really test wide open throttle without going over 6,000 RPM.

She’s got me covered!

I would run it through the same steps discussed in the video running it wide open throttle paying attention to the tachometer and where the RPMs are in relation to the recommended range for that motor. You can go check out Mercury's Prop Selector to get a start too.

Yes, I would drop down in pitch to get those RPMs up, assuming it's a four stroke. You may need to check where your tilt pin is at in the lowest position. Sometimes there's a pull pin or bolts that limit the amount of negative trim the motor can get. Porpoising is usually from not enough negative trim or not enough weight in the bow. You might need to keep those trim tabs down just a bit to limit the porpoising. Either way, I'd want to get those RPMs back up in the operating range which should level out all around performance with whole shot and top speed.

According to this website and chart it looks like 4500-5500 RPM which is typical for a two stroke like that. ptpropeller.warhead.com/images/rich-text/YAMAHA_RPM_GUIDE.jpg

Is it a two or four stroke? Assuming your tach is accurate that's way low for either 2 or 4 stroke motor. You'll want to drop in pitch...remember that each inch you drop in pitch is going to add about 200 rpm to your WOT. Also, make sure you're testing those numbers with an empty boat...not a boat full of people and gear!

Thanks I thought the pitch was to high so a 17p would probably work better ? Thanks Bill

@@mrbowfam dropping 4” would get you to the 4300 rpm range. If it’s a two stroke I’d still want to see it higher. You might end up all the way down at a 15” or even 13” depending what motor you’re running and the specs for WOT operating range. Super common for pontoons to run those lower pitch props!

@@tomspontoons thanks Tom yes it’s a two stroke 75 the boat is 1850 dry ! Do I stay with the same diameter at 12 5/8 ?? Thanks again

@@mrbowfam That's not a super common motor around where I'm from! It looks like it should run anywhere from 4500 to 5500 WOT range from what I found online. The diameter will likely change a little, but I wouldn't be concerned about the diameter. I would probably drop right down to the 13" if it were my boat to try to get those RPMs up in the healthier range!! Not sure you'll see a speed change, but all around torque and control will improve, plus it'll be better for the engine to get the proper high RPMs.

What kind of boat is it on? Pontoon? I would be concerned that your tach might not be reading properly. 8" pitch is very low and would usually have RPMs quite high. For instance, we usually run an 11" pitch on the 60 hp Mercurys that we install and that puts those motors in the sweet spot of around 5700 RPM.

@@tomspontoons all appearances it seems to work properly, idle is correct and it comes up smooth and consistent. it doesn't sound like it is running in the upper rpm range but i will find a way to check that. it is a 23ft pontoon. not sure how to verify the gauge is working correctly but i will do some investigating. Thanks!

@@stockenterprises9391 The only way I really know how to check is to hook in another gauge to the tach sending wire that is new and should be operating correctly. Otherwise you can check the pole/pulse setting on the back of the tach (if it's not a Honda brand gauge). It may need to be changed. They can seem to read accurately to a point in the RPMs and then miss, or they can be way off. I've seen both.

Looks like a 75 hp (1990-2005 years, non optimax) should run 5250 at wide open throttle with an empty boat. You could look to drop to a 13 inch pitch, but might have to watch your RPMs if you’re alone at wide open…however it’ll probably help a lot with when there’s a load of people and it might help with torque to get the bow up a little when trimmed up. A hydrofoil would help too, but not a fix for every boat. It’s a lot of boat to move for a 75 hp so I’m not sure you’ll see a big speed change or improvement either way.

@@tomspontoons thanks for the feedback. Loaded or unloaded (people or gear) it will only hit 5000 rpms. I put a hydrofoil on today and ran it, no improvement. I still can’t get the front end up on the water. I’m assuming the front furniture is too heavy for it. I was hoping to overcome that by the help of a hf and a new prop. I can’t afford to build the motor or buy a bigger one for now so I will try a prop next. So my question now is if I’m trying to gain top end speed do I go to a higher pitch or lower, to the 13 ?

@@MrCornbread1980 I think you’re pretty much seeing your max speed. Lowering in pitch would get your RPMs up slightly, but I don’t see that making any changes to top end speed. There’s a point with every pontoon boat or other non-planing hull where the motor just can’t move enough water to make the boat go faster, despite RPM changes. The boat just doesn’t lift enough compared to a planing hull like a fishing boat or speed boat.

Evinrude props are often labeled on the backside where the exhaust comes out. It may be covered by a nut and washer or just dirty from exhaust. Did you check there? Otherwise you’d need to have a prop shop take a look and they should be able to tell you. If it were my boat, that size with that HP motor I would probably run a 10” or 11” pitch.

@@tomspontoons I did not I’ll take a look thanks

Oh man, that’s far beyond my scope of rigging!!! I would call the boat manufacturer first to see what they recommend, then the dealer to see what’s worked on the other boats they’ve rigged similarly. Then search the outboard manufacturers websites for the testing they’ve done with different boats and motors. From that research you should be able to come up with the information you need to make the smartest purchase possible!! Sorry I can’t be of more specific help on this one!

@@tomspontoons Thanks for your answer, but the manufacturer doesn´t test the twinn rigging. But thanks, It seems I have to get the long way and check by myself dif. setups.

@@7markshark that’s wild that they don’t offer some info. I’d also check with other boat manufacturers of similar hulls and motor setups before making the purchase of two stainless props!!

Best bet is to wire in a new tachometer to see if your tach is just bad. Only a few wires to switch over to the new tach. Without knowing RPMs there’s not much else that you can do. Sounds like you’re probably running a little low of pitch if you have good wholeshot but slow top end. Worst case, might have to have a repair shop take care of it.