Motor height - Merc 150 seapro

[Aquaholic]

As @InterMechanico is implying...Turning Point props are junk. Stick with Mercury/Quicksilver props...they are pretty much the best props around. I run a Mercury/Quicksilver prop on my Yamaha and it is great

Their decades of a highly successful racing program has put them as a leader in propellers.

 

[SpringVelocity]

I don't think a prop is going to do anything honestly speaking from trying various things with exact boat. Your bow is way to light (that is the design). Again shift your weight forward, and also recommend running on 3/4 to full tank. The design of that boat sits heavy in stern. I battled this issue as well with my inboard before podding. Just move your weight around. Lighten the stern first, and keep that foil on if you can.

For transducer I ended up going to thru hull, so not dragging anything. The only other thing I have on my boat vs 182 is that the fuel tank is in center but goes far forward and ends at the cuddy.. I assume you have the same?

 

[Aquaholic]

I don't think a prop is going to do anything honestly speaking from trying various things with exact boat. Your bow is way to light (that is the design). Again shift your weight forward, and also recommend running on 3/4 to full tank. The design of that boat sits heavy in stern. I battled this issue as well with my inboard before podding. Just move your weight around. Lighten the stern first, and keep that foil on if you can.

For transducer I ended up going to thru hull, so not dragging anything. The only other thing I have on my boat vs 182 is that the fuel tank is in center but goes far forward and ends at the cuddy.. I assume you have the same?

Do you know if the boat builder had two different locations for the fuel tank depending on if the boat was built to be an outboard or stern drive? Some other builders do it.

 

[Macdeep]

@Macdeep - Fix the transducer since this is obviously throwing up a ton of spray. I generally agree that you are likely stern heavy, but why not start with raising the motor one more notch?

Here's what I see: In both photos of the anti-cav plate, you are still low. The entire plate should be skimming the surface - I can just see a little bit of it in one of the photos. Unless you are blowing out/venting the prop, motor is too low. Raise it one more, and see where you are at - you are close, but not quite there.

Once the motor is up, it will help the porpoising, but to really address you may need a stern lift prop (typically a 4-blade, but not always). The foils may also help lift the stern, but only if the foils are skimming the surface. If they are buried, it just makes the handling go completely wonky.

Your description of having to run with the motor fully trimmed down to avoid porpoising was exactly what I was dealing with on my etec. I had to raise it 2 holes and switch to a 4 blade. Its a learning experience for sure.

Roger, ya, I have a feeling that raising it a notch is in the cards for sure.

I only posted my situation to confirm what others are telling @Macdeep and give him a comparison/moral support, haha. I am well aware my motor is running low and needs to come up. It is being done next week, while I have the boat in for annual service. Unfortunately, I only have 1 more hole to go before I max out. Hopefully it is enough. Also aware of the trailer tongue lift trick @Max123 noted. I may have gone that route if I wasn't taking it in for other service too - but good info for those that may just need to play with mounting height.

Regarding the question for OP about raising it one hole or two now, I offer an alternative perspective: If you think you might need to go 2 holes, you can go all the way now. If it works, then you're done. If it is too much, you can come back down 1 hole. Someone told me that a year ago, but I thought I was playing it safe and only went up 1 hole. Now I'm going back to go up another hole. If I had just gone 2 to start with it would have been one less motor move.

I appreciate the moral support! Great group here

 

[Macdeep]

At this point I would give you a stainless REV4 just to prove the night and day difference between Aluminum and stainless. but I've suffered enough reading. You're reluctance to explore this is gonna cost ya in the long run, its like wheels on a car except more important Compare this to when you actually need quality ball joints but do tires. I spent 2k on Stainless props when I got my boat and they are paid for in spades. Zero Regrets. Prop is the most important piece on the boat. "Not interested in SS Too $$$" Now this all makes sense.... Thats all i can say.

Ya i get it and I agree that it's the most important part once the rest of the setup is correct. I'm just looking at costs for moving the motor up again, and have the repowering costs that I'm still feeling, so dropping another 2k just isnt in the wallet without some concessions at the other end - I'm getting perimeter drains redone on my house as well as some basement water issues addressed by way of flooring etc, so it's just not great timing. I dont disagree that a SS prop will be worth it just in fuel savings alone, but I'll have to wait till the dust settles on my house projects before I spend any more on the boat besides one last kick at getting the motor height right and a second cheap-o aluminum prop either as a spare or the new main especially if I go with a 4 blade as a final step. I'm even balking at spending 5-600 on a new aluminum prop and going used in the 200$ range if that helps frame where I'm at. I've looked at used SS but they are hard to come by in what I'm after. But I'm calling the prop shop today so will see what they have in stock in my budget. Will dream of an SS prop down the line. I appreciate the advice and take it seriously.

 

[Macdeep]

Alright, after reconsidering...

1) move motor up one notch (possibly 2, but it's already 2" above the hull...)
2) re-balance the weight - thinking if this works, then going up 2 holes will be too much.
3) look into a used SS prop from a prop shop, probably a 4 blade for stern lift.
4) dont get hung up on the foil - if it works ie. is above the water when on step and not causing wash or spray with the new height and weight distribution, use it, but if its still causing spray, ditch it. I have more than enough power to get up on step quickly without the foil, and I have trim tabs to help if I'm heavily loaded or poorly loaded with people etc on big fishing days.

Will be a few weeks at least to get back in with the mechanic, but will post pics again assuming all's well

This has been educational. I appreciate it. Great group here, lots of good advice and expertise.

 

[Max123]

I think you are close on mounting height, one hole should do it. Your photo showed that the anti-cav plate was visible, but not skimming the water. Its close - just no quite there. Each hole gives you a 3/4" rise. Rough rule of thumb is that if you take a straight-edge along the bottom of the hull and extend it back to the anti-cav plate, the underside of the plate should be 1" higher for every 12" from the transom - but that's just a rough guide - mine was higher than that - very much depends on hull shape.

There are a lot of terrible youtube videos on this, but here is the best one I found. It starts off with the motor mounted too low, and then he raises the motor and tests a few different props. It shows you what you should be looking for in terms of how the anti-cavitation plate should be skimming the surface. The visuals are a useful reference.

 

[Pineapple Express]

I think you are close on mounting height, one hole should do it. Your photo showed that the anti-cav plate was visible, but not skimming the water. Its close - just no quite there. Each hole gives you a 3/4" rise. Rough rule of thumb is that if you take a straight-edge along the bottom of the hull and extend it back to the anti-cav plate, the underside of the plate should be 1" higher for every 12" from the transom - but that's just a rough guide - mine was higher than that - very much depends on hull shape.

There are a lot of terrible youtube videos on this, but here is the best one I found. It starts off with the motor mounted too low, and then he raises the motor and tests a few different props. It shows you what you should be looking for in terms of how the anti-cavitation plate should be skimming the surface. The visuals are a useful reference.

I agree with your description of motor mounting height recommendations @Max123 . Motors are often mounted too low and I frequently recommend that people take the time to dial in the mounting height and propeller selection to improve boat handling and efficiency. On my boat it came from the factory with the motor buried...we raised the motor 2 holes (actually went up 3 holes but came back to 2 holes). Also switched to a prop with more blade area and it helps lift the whole boat and rides better in the chop.

I actually think that @Macdeep is close on mounting height. In one of the pics posted you can see part of the anti-ventilation plate visible. It should be more visible when running normally but it's not because @Macdeep is running fully trimmed down. The boat probably needs to have the centre of gravity shifted forward to prevent porpoising....once this is achieved and the motor is trimmed more neutrally I think the mounting height will be close.

@Macdeep can experiment with changing the centre of gravity by utilizing temporary ballast (sand bags, buckets of water, cannonballs, etc) strictly for experimentation. For a small planing hull boat (like this) adding ballast isn't desireable because it will affect the static stability and will reduce the load carrying capacity of the boat. If it is confirmed that the boat runs better with the centre of gravity further forward than it is now the best course of action is to shift heavy items forward (batteries, fuel tanks, etc)

Another experiment would be to remove the kicker and see how the boat runs without that extra 120lbs hanging off the port transom.