Engines,props, and wide open throttle

[Delray]

I’m going to put it in the water Saturday if weather is ok, check cav plate position in water, (engines are already on the lowest hole) and see if I can get anymore rpm’s. At least it’s a start, mechanic says 5500ish should be ok/around where I need to be. Boat comes out of the water quite nicely now, although, it’s just been the two of us.
As I said earlier I’m not a go fast guy so losing some top end isn’t really a big issue for me, I just want it work how it was designed.
Thanks for the replies

 

[kaelc]

I’m going to put it in the water Saturday if weather is ok, check cav plate position in water, (engines are already on the lowest hole) and see if I can get anymore rpm’s. At least it’s a start, mechanic says 5500ish should be ok/around where I need to be. Boat comes out of the water quite nicely now, although, it’s just been the two of us.
As I said earlier I’m not a go fast guy so losing some top end isn’t really a big issue for me, I just want it work how it was designed.
Thanks for the replies

The key to getting this right is a run for Tuna. Let me know some dates and I would be happy to help you out.

On a more serious note chat with an experience Yami dealer about prop selection for the 150. I went to the parts guy at SG and he set me up with a slightly different aluminum prop for my Yami 115 when I had your problem of not getting over 5000rpm and not the best performance. It worked out well and I got to 5600rpm if I remember. I wouldn't be investing $2k in new stainless props if I were you but you might find used ones off the forum/ebay or facebook marketplace.

 

[wolf]

check cav plate position in water,

Correct me if im wrong you check all that with the bottom of your hull? if its too low you will have problems just like being too high there is parameters it has to be in. every boat is different too it can be same boat etc but loads and amounts of stuff make a huge difference
As for RPM you want to be at least the min low range of what the engine secs say if its too low its lugging engine which is hard on it , basically think of it this way you drive up the malahat in 5th gear and engine is really struggling same thing put it into 4th gear fly's up the hill no problems.
I have no clue what the factory specs "range" is for your engine
I know for mine it is 5700 to 6200 and I started a ta 21 pitch couldnt get to the lowest part, then had to go to a 19 and im at 5850 RPM so the dealer was happy at that . always fun fiddling with this ****..... NOT

 

[Thunder21]

Personally I would prop it so when you are running with two people and half fuel or so, you can just hit the redline. This way when you throw 4 people and a pile of gear in the boat you are still going to be in the recommended range. It’s better to cruise at a little higher rpm than to be lugging.

 

[VanIsle10]

Another reason or advantage for propping twin engine setups near the high end of the recommended range is to get better single engine performance if you ever need to run back in on one engine. You will have a better chance of planing on one motor if you can spin more rpm vs lugging it.

 

[Brando]

Correct me if im wrong you check all that with the bottom of your hull? if its too low you will have problems just like being too high there is parameters it has to be in. every boat is different too it can be same boat etc but loads and amounts of stuff make a huge difference
As for RPM you want to be at least the min low range of what the engine secs say if its too low its lugging engine which is hard on it , basically think of it this way you drive up the malahat in 5th gear and engine is really struggling same thing put it into 4th gear fly's up the hill no problems.
I have no clue what the factory specs "range" is for your engine
I know for mine it is 5700 to 6200 and I started a ta 21 pitch couldnt get to the lowest part, then had to go to a 19 and im at 5850 RPM so the dealer was happy at that . always fun fiddling with this ****..... NOT

You do the basic cav plate setup with the bottom of the hull and then confirm with seatrial. Less drag when the cav plate is just above the waterline on plane. I think this boat is pod from factory? So if it’s stepped your probably too low in the water that’s pretty normal. Can be upwards of 2+ up for each 12” back all just depends on the hull itself. Sea trial is the best way to confirm your in the sweet spot.

 

[wolf]

True brando ive see too low looks rather funny with boat on plane...

 

[Delray]

Yes it’s a factory pod. I’ll leave everything alone and check engine height while planing first. Then move on. Thanks for all the replies

 

[Delray]

Nice day on the water today so went for a rip. Trimmed out I hit 5400 rpm at wide open throttle, might have been able to squeeze a bit more out but wifey wasn’t at all comfortable with this exercise. engines may be too a bit low but at least I was into the 5’s. Here is a still taken from a video.

 

[Brando]

It looks like you could come up another hole on the motor mounting height to me if possible hard to say exactly from that shot.

 

[wolf]

It looks like you could come up another hole on the motor mounting height to me if possible hard to say exactly from that shot.

I totally agree... looks to low to me water should be under the cavitation plate not on top.

 

[Delray]

I totally agree... looks to low to me water should be under the cavitation plate not on top.

That is what I think as well, problem being it’s already on the lowest hole now. I may just run with it, then see how to raise during the winter ‍

 

[wolf]

That is what I think as well, problem being it’s already on the lowest hole now. I may just run with it, then see how to raise during the winter ‍

you have to come up not down , for example my cavitation plate is just up almost a inch from the bottom of my pod and its bang on when running.. I think spring Velocity had some sort of table thing I saw him post somewhere

 

[Corey_lax]

you have to come up not down , for example my cavitation plate is just up almost a inch from the bottom of my pod and its bang on when running.. I think spring Velocity had some sort of table thing I saw him post somewhere

He's in the lowest hole, so it cant go up more without new holes.

 

[Brando]

Manual jackplates will solve the problem.

 

[Sharphooks]

I also went to 4 blade, will never run a 3 blade again,hole shot and fuel savings are night and day. A friend of mine has a 682 and a single 250 yam, also running 3 blade 19pitch, slow as hell getting on plane and staying there, he runs it at 4800rpm doing like 32 mph and burns a lot of fuel, loaded he needs to do the shuffle to the front to get on plane lol, told him to change his pitch to 17, won’t do it stuburn old fart lol

In my experience, there isn’t necessarily a direct correlation between improved fuel burn when going from a 3-blade to a 4-blade.

A few summers ago I ran a 4-blade on my DF300 Suzuki and hit a rock hard enough to bend the flukes——I had a 3-blade spare to finish off my trip and the first thing I noticed was my fuel burn decreased by 10 -15% — I was so struck by that improvement that I spiffed up the 4-blade and sold it and ran 3-blades on that DF300 for as long as I owned the boat

But I’ll also add that the 4-blade was a 16” diameter stainless PowerTech prop——that’s a huge prop and not too many outboard can turn it. I think the size and weight of that prop was responsible for that increased fuel burn....moral of the story—-not all 4 blades will lead to better fuel burn....thought I’d throw that in

Meanwhile, based on the OP’s description of RPM issues and configuration of his boat, I agree the 19P is at least part of his problem.....maybe a 17x15 3/4” would get him back on Broadway with mid to upper 5’s at WOT?

 

[wolf]

He's in the lowest hole, so it cant go up more without new holes.

HHMMMM well that sucks weird also as they use a template to make it so you can move it up and down with lots of room , I can only assume they didnt use the template and drilled it while motor was on boat...

 

[brutus]

In my experience, there isn’t necessarily a direct correlation between improved fuel burn when going from a 3-blade to a 4-blade.

A few summers ago I ran a 4-blade on my DF300 Suzuki and hit a rock hard enough to bend the flukes——I had a 3-blade spare to finish off my trip and the first thing I noticed was my fuel burn decreased by 10 -15% — I was so struck by that improvement that I spiffed up the 4-blade and sold it and ran 3-blades on that DF300 for as long as I owned the boat

But I’ll also add that the 4-blade was a 16” diameter stainless PowerTech prop——that’s a huge prop and not too many outboard can turn it. I think the size and weight of that prop was responsible for that increased fuel burn....moral of the story—-not all 4 blades will lead to better fuel burn....thought I’d throw that in

Meanwhile, based on the OP’s description of RPM issues and configuration of his boat, I agree the 19P is at least part of his problem.....maybe a 17x15 3/4” would get him back on Broadway with mid to upper 5’s at WOT?

My fuel burn is better because I can run lower rpm at the same speed, also way faster holeshot, I am sure if I played more with 3 blade pitch I might of done better, I was running 14-3/4x18pitch 3 blade, went to 14-3/4 x15 pitch 4 blade, works great on my boat setup, I run a Honda 225 and when she goes in to vtec mode she is thirsty lol, 4500rpm it kick in

 

[Corey_lax]

HHMMMM well that sucks weird also as they use a template to make it so you can move it up and down with lots of room , I can only assume they didnt use the template and drilled it while motor was on boat...

Maybe a 25” leg on a 20” transom? Or something like that

 

[hippaisland]

You should get at least 5500 rpm and I think the prop change will do it.
As far as running WOT, the older 2 strokes were built for it and could endure.
I wouldn't be running a modern 4-stroke at WOT for any more than a couple minutes
at a time, too hard on the internals.
just my opinion.

Not advising running on WOT with any motor for extended periods but they can certainly endure it for more than a few mins. We used to run the lodge boats at either WOT or idle(trolling) for well over 1000 hours a season. There was no in between. Would I run mine like that, no, but in my humble opinion a properly maintained 4 stroke isn’t going to have any issues running high rpm’s for extended periods with proper warm up/cool down.