Are the Optimax 200, 225 and 250 using the same internals to make the different HP? Looking at Mercury's website it looks that way. Granted I'm not gear head, just dangerous enough to think I know something. If the same block and bore is being used, does the higher HP engines have a high internal temp? On a single rig, is the difference in HP very much noticeable? How about in a twin and triple rig? Thanks Dwight
Hey Dwight - Unfortunately there are very few torque curves available from outboard manufacturers. In my experience you don't want the highest horsepower motor that a manufacturer makes off of a given block (displacement) as many times the max hp means they sacrifice somewhere else to get to that max hp. (at least for show skiing application) The only exception to this rule I know of is the 300 E-Tec which has a different ecu fuel map than the 250HO and a different gear ratio. My guess is in the Optimax lineup the regular 225 or 225 Pro XS are probably the best for show skiing. I have a feeling once you get to 250 Pro XS the emphasis is on max speed and not low end. You'll notice the difference more in a single/twin rig than in a triple rig but in show skiing it is hard to notice because if you run the same prop on a 200 as you do on a 250 with the same gear ratio, until you max that motor/boat out you might not notice any difference. We went with the smallest hp built off the 3.3L block from Evinrude (200HO) on our triple because it is the least expensive and yet the torque is fantastic. Evinrudes typically have 1.86:1 gearing where the Merc Optis 200 and up have 1.75:1 so you need to go to a smaller prop pitch on the Opti to max out your low end pulling power. Hopefully this makes sense and is not just rambling. Erich
Dwight I believe you are correct that the main difference is in the ECM and maybe the size of the throttle body. More fuel and air make more hp. I do not think the internal temp is that much difference because the compression ratio is the same. Yes they make more hp but that requires more fuel which acts to keep the engine cool. I can't comment from experience on the singles or twins but the triples I can and the more hp the more you can pull. Seven years ago we put our first triple with 250hp xs racing engines on a triple which Ron drove. I was skeptical with the same concerns that Erich talked about(racing high hp motors are for racing not for pulling). I was proved wrong they have a bigger torque curve and have a higher rpm. So you get great torque and can run faster speeds because of the higher rpm. I do not have the data on the curves like Erich said a closely guarded secret in the outboard world. Ron pulled 50 with the 250xs racing outboards but took us all morning to get everyone off the dock. Ron pulled 44 at Nationals which I think is about the limit with 250's. Hope this helps Edd
The one thing I have done and you may be able to do it online or at a Merc dealer is compare the part numbers of the engine blocks and ECUs. In Evinrude's case the 200HO/225 and 225HO/250 each share the same components. You can sometimes sort of deduce which model might best suit your needs this way. My guess is you'd be happy with any triple with 225/250.
Mercury did publish the torque and horsepower curves for the 250xs and the 300xs when they first came out. I had them in my computer for years, but I must have deleted them. I never expected the issue to come up here. From memory the 250xs produces about 270 hp and had a broad torque curve with good mid range. It would also run on 87 octane which made it a real bargain. I think the 300xs produced about 330 hp, also with a broad torque curve. It required premium fuel. I think Mercury was pretty proud of the numbers and published the data on their site. I was surprised at the numbers to say the least. I also searched Scream and Fly because I posted the stuff there, but I could not find it. It would be a pretty old post. Dynebob has a 250xs on his 18 and maybe he will see this. That is a very potent motor. Don't forget that these xs motors with a low pitch ski prop will have a pretty sensitive throttle on a light boat. jim
When I purchased the 250XS for my 18 footer, I kind of expected the things that go along with a high performance engine. ( hard starts...rough idle...loading up during long idle periods..etc.) Much to my supprise..none of that. Mercury hit a home run with this series of engines. It has all the low end power you'd need..great mid-range...super top end..and even decent fuel consumption if you don't push it real hard. Jim was right on about the throtle control with a light boat. Dialing in and keeping a low speed with this engine and the stock Mercury controls proved to be a chore. I spoke to a few of the drivers at the nationals, and they suggested to get rid of the Merc controls in favor of the dual lever. I purchase and installed the dual lever Livorsi unit, and now can control the slow speeds much better. The only time I have to tweek it is when pulling into long gentle turns, and a slight twitch of the wrist does it. Propped with a 19 pitch High-Five, it pulls like a freight train but still has a great top-end. Bob
I saw Merc's numbers too but didn't keep them - or at least can't find them right now. Here is Evinrude's take.
