Engine selection

[titus14]

Hello all,

This is my first post, although I've gotten tons of useful information from this forum as a non-member in the past, so firstly, thank you all. However, I have a few questions now, because I'm in a tight spot.

In Louisiana, we typically don't need to winterize until late in the year because the warm temperatures allow us to play on the water sometimes as late as November. However, in October I was hospitalized due to cancer, and never got the chance to do my yearly duty to my 2008 Crownline 180BR. Now, due to an extremely cold winter, I'm replacing the entire engine due to a cracked block, and intake and exhaust manifolds. Rather than waste time crying about it, I'm really looking forward to upgrading, but I need some education on my options.

I've already purchased a new 4.3L and stuck with the carb'd intake. I know the MPI is better on throttle response, but I've towed plenty of fuel-injected fellow boaters to the dock, and I don't trust it. The engine I did purchase is directly from the Mercury Marine, and listed at 210hp, and will work with my existing carb and alternator, saving me some cash. This is 20hp above the setup I had, and the mechanic said he could jet the carb to give me approximately the same hp as the 4.3MPI. My question is throttle response. Has anyone ever played with the jets on a stock 2bbl and gotten a gain? I'm looking for low end power with this set-up, not top end speed. I use a 4 blade 20 pitch Mercury prop, which gets me 38mph with a loaded boat and 4 adults at 3700rpm, (I NEVER over-rev), and I've taken it to 45mph at 4600rpm unloaded with just me in the boat. But it used to drag coming out of the water with a lot of weight in the stern. I need to know if this new setup will stress my out-drive with the increased hp. It uses a 1.81 gear ratio, and I know the 220hp MPI uses a 1.62. I don't mind re-propping, but since I'm making some changes, I'd like to hear some advice from more experienced people than I.

 

[Bondo]

Re: Engine selection

Hello all,

This is my first post, although I've gotten tons of useful information from this forum as a non-member in the past, so firstly, thank you all. However, I have a few questions now, because I'm in a tight spot.

In Louisiana, we typically don't need to winterize until late in the year because the warm temperatures allow us to play on the water sometimes as late as November. However, in October I was hospitalized due to cancer, and never got the chance to do my yearly duty to my 2008 Crownline 180BR. Now, due to an extremely cold winter, I'm replacing the entire engine due to a cracked block, and intake and exhaust manifolds. Rather than waste time crying about it, I'm really looking forward to upgrading, but I need some education on my options.

I've already purchased a new 4.3L and stuck with the carb'd intake. I know the MPI is better on throttle response, but I've towed plenty of fuel-injected fellow boaters to the dock, and I don't trust it. The engine I did purchase is directly from the Mercury Marine, and listed at 210hp, and will work with my existing carb and alternator, saving me some cash. This is 20hp above the setup I had, and the mechanic said he could jet the carb to give me approximately the same hp as the 4.3MPI. My question is throttle response. Has anyone ever played with the jets on a stock 2bbl and gotten a gain? I'm looking for low end power with this set-up, not top end speed. I use a 4 blade 20 pitch Mercury prop, which gets me 38mph with a loaded boat and 4 adults at 3700rpm, (I NEVER over-rev), and I've taken it to 45mph at 4600rpm unloaded with just me in the boat. But it used to drag coming out of the water with a lot of weight in the stern. I need to know if this new setup will stress my out-drive with the increased hp. It uses a 1.81 gear ratio, and I know the 220hp MPI uses a 1.62. I don't mind re-propping, but since I'm making some changes, I'd like to hear some advice from more experienced people than I.

Ayuh,.... With the 2bbl. carb, yer gonna get 190 hp, at the most,....
It'll be exactly the same as yer old cracked motor,...

To get 210 hp or Better, ya need a 4bbl. carb, or Efi,....

 

[titus14]

Re: Engine selection

Thanks Bondo. Do they list it as 210 at the flywheel and 190 at the prop? Because they sure explained it as a 20hp upgrade, and that was from the factory, not the mechanics. In reference to the other questions, if I do change intakes and carbs, will I over stress that drive assembly?

 

[Bondo]

Re: Engine selection

Thanks Bondo. Do they list it as 210 at the flywheel and 190 at the prop? Because they sure explained it as a 20hp upgrade, and that was from the factory, not the mechanics. In reference to the other questions, if I do change intakes and carbs, will I over stress that drive assembly?

Nope,... but ya might need a taller pitched prop,...

 

[achris]

Re: Engine selection

...I'm looking for low end power with this set-up, not top end speed. I use a 4 blade 20 pitch Mercury prop, which gets me 38mph with a loaded boat and 4 adults at 3700rpm, (I NEVER over-rev), and I've taken it to 45mph at 4600rpm unloaded with just me in the boat. But it used to drag coming out of the water with a lot of weight in the stern.....

Some history with my boat before we get into your setup. I have a nice heavy 20' cuddy. Had a 165 in from day one (May 1972) and when I bought it (in 1986) the prop was a 17". Those old in-line 6s were specced to 3900-4300. With the 17" prop she barely made 3900, and was a dog. Took forever to come on the plane and was like trying to drive around an old boot. I changed it for a 15" (WOT now 4350) and the difference was chalk and cheese. The whole boat felt more 'alive'. It would pop straight onto the plane, was much more responsive to the throttle, would turn on a dime and it used less fuel. In 1994 I replaced the very tired 165 with a nice shiny 4.3LX.. 4bbl 180hp at the prop, and 1.81:1 drive. Having had the experience with the 2 different props on the 165 I opted to go straight to a prop that would get me right up to the top end of the spec. This engine was recommended to run 4400-4800rpm at full noise. With a 21" Laser II prop she was pulling just on 5000, and loved it. I ended up running most of the time with a 20" 4 blade SS prop which would pull about 5100 if I let it. In 2006 I changed the engine again, to another nice shiny new 4.3MPI, this time with a 1.62:1 drive. I had to again re-prop, which meant selling all the other props (I usually have 4 or 5 different props) and buying a bunch more. When I first got the MPI I found it seriously lacking in torque in the mid-range. I ended up propping with a 17", which runs right into the rev-limiter, at 4950. If I put the 19" she's right on 4600, but is back to the old 'dog-like' performance. So, the 17" SS 'Vengance' prop is my everyday prop. Oh, that lack of mid-range torque has been solved by allowing the engine to run-in properly...

Ok... I hear you saying I'm over-revving. Yes I am. But, these 4.3s are quite happy with that. You won't do them any damage, in fact you'll be doing them (and yourself) a favour. That previous engine (the 4.3LX) is in a friends' boat now, and still going strong. When I bought that engine new I put closed cooling on it, and a pair of SS exhaust elbows... Almost 2000 hours on it and the only things that have been changed, apart from regular service items (oils, filters, spark plugs and water pump impeller), are the uni bellows, the oil pan (and I also galvanised the new one) and an ignition coil (water dripped onto it and rusted out the bottom). That's all!

Now, to your boat/engine set up. As Bondo has already pointed out, 190hp. Re-jetting the carb will not change anything, apart from use more fuel. Remember that the optimum air/fuel ratio is about 14:1. That give maximum usage of fuel. If it's richer then there is not enough oxygen to burn all the fuel, same power, but un-burnt fuel is headed out the exhaust... Leaner and there is not enough fuel to fully use all the oxygen, which will produce less power, and also burn valves because the combustion temperatures will be higher.

Another advantage of a lower pitch prop is it takes the load off the engine, and that goes for the entire rev range. The engine experiences less wear, the drive experiences less wear and doesn't get as hot. The engine bearings don't get pounded out, and the boat is a whole lot nicer to drive.

As for the 1.81:1 drive... Great! The higher the prop pitch the more efficient the prop. That's the one thing I regret with my engine, not speccing the higher reduction drive. Don't worry about stressing the drive. These drives are good to about 300hp.

So, when you put your new engine in, prop it up to at least the top of the range (4800rpm), and if your over a bit, even a couple of hundred revs, that's a bonus.... You did say it 'dragged a bit' coming out of the water, that's because you have too much pitch. I'm not sure if you use the boat in the ocean or on the river or lakes, but if it's ocean work, then as you climb and run down swells, with a big prop you'd notice the falling off of boat and engine speed as you climb, then a lot of increase in both as you run down the face of the swell. All this means a lot of throttle work to maintain a constant speed. Put a lower pitch prop on and that problem is gone, near constant speed at all times.

I honestly can't think of any reason not to prop right to the top of the rev range, especially with the crappy fuels we have these days....

HTH,

Chris........

 

[Bondo]

Re: Engine selection

Some history with my boat before we get into your setup. I have a nice heavy 20' cuddy. Had a 165 in from day one (May 1972) and when I bought it (in 1986) the prop was a 17". Those old in-line 6s were specced to 3900-4300. With the 17" prop she barely made 3900, and was a dog. Took forever to come on the plane and was like trying to drive around an old boot. I changed it for a 15" (WOT now 4350) and the difference was chalk and cheese. The whole boat felt more 'alive'. It would pop straight onto the plane, was much more responsive to the throttle, would turn on a dime and it used less fuel. In 1994 I replaced the very tired 165 with a nice shiny 4.3LX.. 4bbl 180hp at the prop, and 1.81:1 drive. Having had the experience with the 2 different props on the 165 I opted to go straight to a prop that would get me right up to the top end of the spec. This engine was recommended to run 4400-4800rpm at full noise. With a 21" Laser II prop she was pulling just on 5000, and loved it. I ended up running most of the time with a 20" 4 blade SS prop which would pull about 5100 if I let it. In 2006 I changed the engine again, to another nice shiny new 4.3MPI, this time with a 1.62:1 drive. I had to again re-prop, which meant selling all the other props (I usually have 4 or 5 different props) and buying a bunch more. When I first got the MPI I found it seriously lacking in torque in the mid-range. I ended up propping with a 17", which runs right into the rev-limiter, at 4950. If I put the 19" she's right on 4600, but is back to the old 'dog-like' performance. So, the 17" SS 'Vengance' prop is my everyday prop. Oh, that lack of mid-range torque has been solved by allowing the engine to run-in properly...

Ok... I hear you saying I'm over-revving. Yes I am. But, these 4.3s are quite happy with that. You won't do them any damage, in fact you'll be doing them (and yourself) a favour. That previous engine (the 4.3LX) is in a friends' boat now, and still going strong. When I bought that engine new I put closed cooling on it, and a pair of SS exhaust elbows... Almost 2000 hours on it and the only things that have been changed, apart from regular service items (oils, filters, spark plugs and water pump impeller), are the uni bellows, the oil pan (and I also galvanised the new one) and an ignition coil (water dripped onto it and rusted out the bottom). That's all!

Now, to your boat/engine set up. As Bondo has already pointed out, 190hp. Re-jetting the carb will not change anything, apart from use more fuel. Remember that the optimum air/fuel ratio is about 14:1. That give maximum usage of fuel. If it's richer then there is not enough oxygen to burn all the fuel, same power, but un-burnt fuel is headed out the exhaust... Leaner and there is not enough fuel to fully use all the oxygen, which will produce less power, and also burn valves because the combustion temperatures will be higher.

Another advantage of a lower pitch prop is it takes the load off the engine, and that goes for the entire rev range. The engine experiences less wear, the drive experiences less wear and doesn't get as hot. The engine bearings don't get pounded out, and the boat is a whole lot nicer to drive.

As for the 1.81:1 drive... Great! The higher the prop pitch the more efficient the prop. That's the one thing I regret with my engine, not speccing the higher reduction drive. Don't worry about stressing the drive. These drives are good to about 300hp.

So, when you put your new engine in, prop it up to at least the top of the range (4800rpm), and if your over a bit, even a couple of hundred revs, that's a bonus.... You did say it 'dragged a bit' coming out of the water, that's because you have too much pitch. I'm not sure if you use the boat in the ocean or on the river or lakes, but if it's ocean work, then as you climb and run down swells, with a big prop you'd notice the falling off of boat and engine speed as you climb, then a lot of increase in both as you run down the face of the swell. All this means a lot of throttle work to maintain a constant speed. Put a lower pitch prop on and that problem is gone, near constant speed at all times.

I honestly can't think of any reason not to prop right to the top of the rev range, especially with the crappy fuels we have these days....

HTH,

Chris........

Ayuh,.... Agreed,....

If nothin' else, it gives ya a wider window before Detonation goes from "Oops" to "Oh, Ship",.... :lol:

I'd drop an Edlebrock 1409, 'n intake on it, 'n go have Fun,....

 

[achris]

Re: Engine selection

Some history with my boat before we get into your setup. I have a nice heavy 20' cuddy. Had a 165 in from day one (May 1972) and when I bought it (in 1986) the prop was a 17". Those old in-line 6s were specced to 3900-4300. With the 17" prop she barely made 3900, and was a dog. Took forever to come on the plane and was like trying to drive around an old boot. I changed it for a 15" (WOT now 4350) and the difference was chalk and cheese. The whole boat felt more 'alive'. It would pop straight onto the plane, was much more responsive to the throttle, would turn on a dime and it used less fuel. In 1994 I replaced the very tired 165 with a nice shiny 4.3LX.. 4bbl 180hp at the prop, and 1.81:1 drive. Having had the experience with the 2 different props on the 165 I opted to go straight to a prop that would get me right up to the top end of the spec. This engine was recommended to run 4400-4800rpm at full noise. With a 21" Laser II prop she was pulling just on 5000, and loved it. I ended up running most of the time with a 20" 4 blade SS prop which would pull about 5100 if I let it. In 2006 I changed the engine again, to another nice shiny new 4.3MPI, this time with a 1.62:1 drive. I had to again re-prop, which meant selling all the other props (I usually have 4 or 5 different props) and buying a bunch more. When I first got the MPI I found it seriously lacking in torque in the mid-range. I ended up propping with a 17", which runs right into the rev-limiter, at 4950. If I put the 19" she's right on 4600, but is back to the old 'dog-like' performance. So, the 17" SS 'Vengance' prop is my everyday prop. Oh, that lack of mid-range torque has been solved by allowing the engine to run-in properly...

Ok... I hear you saying I'm over-revving. Yes I am. But, these 4.3s are quite happy with that. You won't do them any damage, in fact you'll be doing them (and yourself) a favour. That previous engine (the 4.3LX) is in a friends' boat now, and still going strong. When I bought that engine new I put closed cooling on it, and a pair of SS exhaust elbows... Almost 2000 hours on it and the only things that have been changed, apart from regular service items (oils, filters, spark plugs and water pump impeller), are the uni bellows, the oil pan (and I also galvanised the new one) and an ignition coil (water dripped onto it and rusted out the bottom). That's all!

Now, to your boat/engine set up. As Bondo has already pointed out, 190hp. Re-jetting the carb will not change anything, apart from use more fuel. Remember that the optimum air/fuel ratio is about 14:1. That give maximum usage of fuel. If it's richer then there is not enough oxygen to burn all the fuel, same power, but un-burnt fuel is headed out the exhaust... Leaner and there is not enough fuel to fully use all the oxygen, which will produce less power, and also burn valves because the combustion temperatures will be higher.

Another advantage of a lower pitch prop is it takes the load off the engine, and that goes for the entire rev range. The engine experiences less wear, the drive experiences less wear and doesn't get as hot. The engine bearings don't get pounded out, and the boat is a whole lot nicer to drive.

As for the 1.81:1 drive... Great! The higher the prop pitch the more efficient the prop. That's the one thing I regret with my engine, not speccing the higher reduction drive. Don't worry about stressing the drive. These drives are good to about 300hp.

So, when you put your new engine in, prop it up to at least the top of the range (4800rpm), and if your over a bit, even a couple of hundred revs, that's a bonus.... You did say it 'dragged a bit' coming out of the water, that's because you have too much pitch. I'm not sure if you use the boat in the ocean or on the river or lakes, but if it's ocean work, then as you climb and run down swells, with a big prop you'd notice the falling off of boat and engine speed as you climb, then a lot of increase in both as you run down the face of the swell. All this means a lot of throttle work to maintain a constant speed. Put a lower pitch prop on and that problem is gone, near constant speed at all times.

I honestly can't think of any reason not to prop right to the top of the rev range, especially with the crappy fuels we have these days....

HTH,

Chris........

Ayuh,.... Agreed,....

If nothin' else, it gives ya a wider window before Detonation goes from "Oops" to "Oh, Ship",.... :lol:

I'd drop an Edlebrock 1409, 'n intake on it, 'n go have Fun,....

You must have been reading this as I typed it... That was a very fast response..

And I completely agree with the Edlebrock and intake....

 

[titus14]

Re: Engine selection

Chris and Bondo, you've helped me out a lot. Thank you very much! I just ordered a new 18 pitch 4-blade a few minutes ago, and hopefully that will suffice for now. I'll have to try a bit harder to convince the better half that we need more engine parts for the new engine. But, I'll save that conversation for another forum. Again, thanks for all your help!

 

[Walt T]

Re: Engine selection

Just clarifying for others, Fuel jets do not increase power on their own unless there is a serious mismatch. Increasing or decreasing fuel only changes mixture ratio with incoming air and the incoming air is a constant relatively speaking. As throttle plates move, air is regulated and fuel is metered to that air. This is true no matter what intake you are running. with TBI, EFI, MPI, EPA, FBI, CIA, NSA, there is more precise control of the fuel being metered which makes the engine respond way better than a carburetor. Nothing wrong with carbs, they're great when properly set up.
Those who claim big HP increases by changing jets and power valves I would submit the carburetor was not set up properly to begin with and your motor wasn't putting out max HP to begin with.
More power is obtained by burning more air and fuel in a set period of time. However your engine is limited to how much it can burn by the size and rpm limits. Bigger motor is more HP- usually, but they do produce more torque at lower rpms. Higher rpm theoretically is more HP but only if the engine is set up to use it.