Why Did Indmar Reinvent The Wheel?

[Germaine Marine]

Once you know ratio Josh, we can see where the tradeoff is. If its a 1.7 My guess is you will end up being around the 15.5 x 13 or 15.5 x 14. That should bring you down roughly 250-300 rpm plus from where you are now if you are running a 15 x 12 with a gain in bottom end bite and a little gain in top end as well. The bigger diameter is key if that ratio is around 1.7 you should be able to push into the 16s without issue..... the question mark like ive said is ration and clearance.

[UNSTUCK]

The prop on there now is a 2315. The trans tag has two ratios on it: 1.46 and 1.51. Not sure which it is but they aren't much different. The trans model number is ZF45IV. I have 7/8" clearance to the hull and 1 5/8" to the prop guard. Nettles is expecting to get at least one prop ha I from me soon. I can swap out to a 15.5 if you guys think that's the answer. The guy at acme was having a hard time explaining the difference between a larger prop with more pitch vs a smaller one with less pitch. Seems to me they cancle each other out.
I would be very happy if it was just a prop swap. I have to admit I'm doubting.

[talltigeguy]

Am I the only one that thinks that 5350 pounds ballast with a heavy rear bias may simply be too much for this engine /tranny combo? Without a 2:1 ratio and a 17 inch prop, I think you may be fighting a losing battle.

I love hearing the gear heads talk, and admire your drive to get the max from the boat.

[UNSTUCK]

I love hearing the gear heads talk, and admire your drive to get the max from the boat.

I'm kind of weird this way. To me it sounds like a great idea and a lot of fun to build a new harness for this engine that will allow it to run on GM ecm. Then throw some parts at it and tune. Walk away with 450-500 hp no sweat.

[Germaine Marine]

So why are you running a less aggressive prop 2315 vs 2419?

If you only have 7/8 then we could push maybe to a 15.5 and try it. Take it run it for 10 and see if we have any prop burn...

I still think a prop can fix all of your issues.

[freeheel4life]

As usual, late to the chatter. Been super stimulating so far. I'm curious what aftermarket cam swap you are looking at it. Also there is a bunch of Raptor talk flying around. I don't follow MB that closely, but I know for many years they had a bunch of 343, 409, and ZR6 PCMs crammed in them. Sounds like you have and Indmar pre Raptor, assuming M60...just haven't had the chance to see this configuration and was curious if it was just a few years in between.

Did MB also option out the 5.7 in this same weird crossover. Or am I just missing the boat completely??

[chpthril]

The prop on there now is a 2315. The trans tag has two ratios on it: 1.46 and 1.51. Not sure which it is but they aren't much different. The trans model number is ZF45IV. I have 7/8" clearance to the hull and 1 5/8" to the prop guard. Nettles is expecting to get at least one prop ha I from me soon. I can swap out to a 15.5 if you guys think that's the answer. The guy at acme was having a hard time explaining the difference between a larger prop with more pitch vs a smaller one with less pitch. Seems to me they cancle each other out.
I would be very happy if it was just a prop swap. I have to admit I'm doubting.

On paper. When you go up in diameter, the rpm drop. When you go down in pitch, rpm increase. When you make changes in both when moving to a new prop, the effects of each offset each other. Not necessarily cancels each other out, but each measurement change offsets the other to some degree. So why go up up dia and down in pitch only to have the positive effects of one or both, washed out by the other? Good questions. When you go up in diameter, you are adding surface are to each blade. This adds bit or grip. Overall, it improves the props performance. Just making a pitch drop will increase hole shot, but without adding the extra surface area, we mat still get slip and cavitation. Depending on the load, to get the hole shot we need, the drop in pitch may just increase the rpm too much. Going up in diameter offsets some of that rpm increase, but we still gain some holeshot performance from the pitch drop.

The hull/trailer are going to physically determine the max diameter we can go. However, the engine will also. We can only drive so much wheel. This is where the newer v-drive ratios are coming into play on these boats driving the 15+ inch wheels. We are able to spin the large props through gear reduction without robbing horse power to do it.

The engine is also going to limit the drop in pitch. At some point, the RPMs are too high and we are out of a usable power curve of the engine.

[Germaine Marine]

I don't need to echo what Mike said...

Unless your motor is hurt I can't see why it's having so much trouble. The 400 raptor with the 2419 and 1.5-1 is an absolute monster at elevation with 4500 lbs of weight. You are another grand, and that may be a big problem especially if that motor power wise is inferior.

Go up to a 15.5 x 13 or 15.5 x 14 and let's see what happens.

[UNSTUCK]

Acme recommended the 2315 hoping it would be enough, knowing that the 2419 would be the next recommendation if it wasn't.

[Germaine Marine]

Go to 15.5 and take the risk

[Bakes5]

Am I the only one that thinks that 5350 pounds ballast with a heavy rear bias may simply be too much for this engine /tranny combo? Without a 2:1 ratio and a 17 inch prop, I think you may be fighting a losing battle.

Nope...your situation sounds exactly like an "I got too much ballast" situation. Kinda like when I am experimenting around with seeing how much prop I can get away with. Seriously, you are 5350 ballast + 4400 boat = 10,000 lbs minimum without people, gear, fuel, etc. Let's just be conservative and call it 11,500 pounds in the water. All the newer boats pushing that either have the 575 or a 2:1 tranny or both. I don't think any tune/cam is going to fix that. Forced induction and lower gear ratio should do it though. With either the cam, tune or super charger you are going to up-end reliability though. If I understand Elevated, it sounds like the newer Tiges come with a 2:1 tranny option and 1 1/4 underwater gear to prevent a Nautique like situation where the shaft fails.

In other words, given the rise of the 2:1 ratios and 575 motors with the 11-12K pound boat crowd, your situation is known and has been re-engineered for. I would never mess with a recreational towboat engine like you are talking about. These boats are meant to be run...not tinkered on or hot rodded to the point it will leave you and your family stranded out on some lake at dusk with a storm a brewin.

I still maintain that the search for the perfect surf wave can cause waaaay too much stress and lack of satisfaction than it's worth sometimes. I think you should go back to your original maiden voyage where you had a "surfable" wave and just enjoy it. Sounds like you can get where you need to with an 11 pitch prop and 4K RPM. That said....you are putting significant stresses on your 1 1/8 shaft going 11-12K pounds.

Anyways, just my opinions. I think you should just spend the money on a hydrofoil and you will be waay ahead in terms of fun.

[dakota4ce]

Unstuck:

I run a 2937 at 1000' and full ballast with small crew and rpm is 4000. Running 13 people mostly adults would never happen. I would have to sacrifice ballast.

I would personally run 800# in rear lockers with 500 in bow and slappers and enjoy the ride. That should and would be a killer wave.

Or go spend 140k on a huge supercharged boat.


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[dakota4ce]

I have also run a .150 cupped 15x11 and that drops rpm to 3700 or so, but when it's super hot outside, it isn't happening.

Slap that boat, run a little less weight and you should have a great combo of big boat, good wave.


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[Germaine Marine]

The 2-1 is going to eliminate the need for big HP very very soon... few more tweaks from the big makers regarding strut and shaft angle and a 400HP/430 Tq small block mated to the 2-1 will be able to push 12k ish without problem.... That 2-1 has made me a believer.

[Germaine Marine]

Unstuck:

I run a 2937 at 1000' and full ballast with small crew and rpm is 4000. Running 13 people mostly adults would never happen. I would have to sacrifice ballast.

I would personally run 800# in rear lockers with 500 in bow and slappers and enjoy the ride. That should and would be a killer wave.

Or go spend 140k on a huge supercharged boat.


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I think hes asking a lot with what he has ration and motor wise... Im with you 100% dump the weight, slap it and be good to go.