Max power from engine

[drgibson]

What do you engine guys do to make sure that you are getting max hp from your engine? I have this vague feeling that I may have lost some power on teh shotshot. I only notice it when pulling up a big slalom skier. The engine starts easily, idles smoothly, and runs at 36 smoothly but while I used to be able to pull up both my sons on slaloms at the same time, now I can barely get one up. Granted he weighs a lot more than before. Everything may be ok but I know a gradual lose of power is sometimes hard to detect. I replaced plugs, wire, roter and dist. cap last year. I ran a bottle of injector cleaer early this year and noramally run mid-grade gas since one of my patients who works for an oil production company, told me that midgrade is a lot "cleaer" than regular. BTW, prop is a 13X13 Acme by Tige's recommendation. I wish this marinepower engine had a ODBII port on it but it doesn't. Any ideas??

[chpthril]

And how much profit did the oil co's post last year??????????????????

The GRADE or octane level have nothing to do with how clean the gas burns, or how clean it is going in your tank!

The octane # refer to the heptane/octane ratio. 87octane is 87/13 and 89 oct. is 89/11 and so on.

The lower the octane value, the less heat it takes to ignite the air/fuel mixture. 87 takes a little heat, 89 takes a little more 91 needs more heat, etc.

In other words, the lower the number on the pump, the less heat needed to ignite.

Once ignited, the rate on burn is the same. gas is brewed this way to prevent spark knock (pre ignition), that nasty 'pinging' sound.

I would ckeck and see how much gear you have added to your boat over the years, and also check the hull and prop.

[dogbert]

Originally posted by chpthril
And how much profit did the oil co's post last year??????????????????

The GRADE or octane level have nothing to do with how clean the gas burns, or how clean it is going in your tank!

The octane # refer to the heptane/octane ratio. 87octane is 87/13 and 89 oct. is 89/11 and so on.

The lower the octane value, the less heat it takes to ignite the air/fuel mixture. 87 takes a little heat, 89 takes a little more 91 needs more heat, etc.

In other words, the lower the number on the pump, the less heat needed to ignite.

Once ignited, the rate on burn is the same. gas is brewed this way to prevent spark knock (pre ignition), that nasty 'pinging' sound.

I would ckeck and see how much gear you have added to your boat over the years, and also check the hull and prop.

One thing you forgot to mention is that it's more difficult to control the firing at lower octane rates. Engines these days are really dialed in, especially if you have an MPI. Running at the wrong octane level can make it difficult to start and idle rough, especially when the engine's hot.

[chpthril]

That's so true, Dog.

[drgibson]

Originally posted by chpthril
And how much profit did the oil co's post last year??????????????????

The GRADE or octane level have nothing to do with how clean the gas burns, or how clean it is going in your tank!

As you well know, the oil companys made some major profits last year, but not from me buying 30 gallons of midgrade rather than regular. I hope my divendends in my ExxonMobil stock reflect that major increase in profits or I'm probably going to agree with you even more. The guy that made the comment to me, was employed by Fina I think, and was a refining consultant. I know where he lives and what he drives, and believe me, he is not seeing the excess profits going in his pocket. His comment to me was that the midgrades fuels are more pure and cleaner than regular. I don't know why he thinks that but I know he is not profiting from me buying whatever so you can take the advice or ignore it. I understand your point however and am reminded that MarinepowerUSA recommended that I run regular. If it makes a difference however, the regular gas here is 86 octane and mid is 88. In Dallas (for example) regular is 87. Whether or not, one point of octance makes difference or not I don't know. The advice was only addressing the cleanliness of the fuel, nothing more.
To answer other points, the engine starts and runs smoothly whether it is cold or hot. I never hear a ping or a miss at any rpm. The prop is in good condition. We try to limit the amount of gear we take so as to not load up the boat too much. However, the kids are not teenagers anymore and the skier in question is quite a bit heavier than before which is probably part of the problem BUT we have both skied behind other boats and are aware they pull harder than ours does. I understand my 98 21i is about 400 lbs heavier than other similar boats which also makes a difference.
Now, what exactly are you referring to when you say check the hull? Does it need to be waxed like the rest of the boat or what?
David

[bneub]

Was the change in performance after you changed your prop, or have you always had that prop?

[drgibson]

I bought the prop two years ago to improve the holeshot. It is (or was) the same pitch as Tige is putting on their new boats of this size and I suppose it is a little better, but not much. I had the opportunity to run it wide open with only me in the boat about a month ago and it ran faster top end.than it ever has before. I just feel like I'm tied to a tree when pulling my son up and probably him pulling me, but we are big guys, 6" 3" and 260+ lbs. The head of service at my regular boat dealer is going to look at it with me after Labor day when his business slows down a little. I wish there was a way to put it on an engine computer like you do with a car and be sure it's not losing something somewhere. This same thing happened last year (or the year before, I forget) and I changed the plugs, wires, rotor, and distrib cap and it picked up a nice amount of acceleration. It was also late in the season and cooler which seems to be a bigger factor than I first realized. We haven't run it much this year due to my broken foot but I'm healed and we want to ski as much as we can before it cools off. The boat mechanic suggested we run the blower more as it gets rather hot under the motor cover in the middle of summer.

[chpthril]

drgibson,

Was not my intesion to say that your customer was giving you false info, but the Oil Co's do want us to believe, through advertising, that high octane burns cleaner, When, infact, the EPA requires certain additives to be put in all Grades to reduce harmfull emissions. Yes, the Oil Co's do put in thier own proprietary additives which may or may not reduce pollution.

A funny side to this is that all the refined fuel goes into the same pipe-line system in Texas. When Exxon pulls up the the distribution center in, lets say NY, they are not getting out thier gasoline that they pumped in the the pipe-line that morning. It's all mixed together with BP, Shell, etc.

If you ever watch the 'Modern Marvals' series on History Channel, they have one on the rifining industry that is realy good.

[bneub]

Originally posted by drgibson
I bought the prop two years ago to improve the holeshot. It is (or was) the same pitch as Tige is putting on their new boats of this size and I suppose it is a little better, but not much. I had the opportunity to run it wide open with only me in the boat about a month ago and it ran faster top end.than it ever has before. I just feel like I'm tied to a tree when pulling my son up and probably him pulling me, but we are big guys, 6" 3" and 260+ lbs.

Is your wide open throttle RPM where it should be after you changed props?

What boat and motor do you have?

[drgibson]

Originally posted by chpthril
drgibson,
Was not my intesion to say that your customer was giving you false info, but the Oil Co's do want us to believe, through advertising, that high octane burns cleaner, When, infact, the EPA requires certain additives to be put in all Grades to reduce harmfull emissions. Yes, the Oil Co's do put in thier own proprietary additives which may or may not reduce pollution.

I agree. I don't think all the additives are promoted to increase mileage but basicly, it is the additives that make a regional brand different from Exxon or Shell. Now, if we just knew if the additives were worth it or not. I understood my patient to mean the fuel was cleaner when pumped into the boat, not necessarily burning cleaner but perhaps they are the same thing.

Originally posted by chpthril

A funny side to this is that all the refined fuel goes into the same pipe-line system in Texas. When Exxon pulls up the the distribution center in, lets say NY, they are not getting out thier gasoline that they pumped in the the pipe-line that morning. It's all mixed together with BP, Shell, etc.

Yeah, he told me that a couple of months ago. I never knew that but once had an executive of a local supermarket chain that also sells gas, tell me the trucks that fill their tanks, went directly to major brand stations and filled their tanks too. I wasn't sure he was telling me the truth but now I guess he was. My patient told me that basic gasoline has certain specifications that all refiners have to meet and it's that product that is shipped to regional distribution points. When a truck bound for an Exxon station pulls in, they add certain additives in and when the truck is headed for Conoco, a different set of additives is added to the basic gasoline. After I thought about it, it made perfect sense.

BTW, I had a "duh" moment this morning and decided to call Marine Power and ask my questions. The tech guy said there was no significant difference in reg and midgrade for this engine. He suggested I check my fuel pump presure and said that there is a plug on the engine to attach a engine evaluator (called a Tech Mate) which would probably do what I would like done but he didn't think the Mercruiser version would read the Marine Power engine computer. The closest Marine Power dealer is about 10 hours away. Suddenly I wish I had a Mercruiser.

[drgibson]

Originally posted by bneub
Is your wide open throttle RPM where it should be after you changed props?

Good question, I wish I remembered what the wide open throttle RPM is supposed to be but I think I did know that at one point in time. I believe I can run it up to 4500 rpm's without concern and I think I ran it up to 4700 or so last month.

Originally posted by bneub

What boat and motor do you have?

It's a 98 21i with a Marine Power engine. The engine is a GM 350 EFI rated at 315 HP.

[bneub]

I don't know what the WOT for your 98 is supposed to be. My dealer said they want my 06 to be about 4800. Might be worth checking to make sure you are getting enough RPM's.

[drgibson]

Good point, I'll check it out. I know that somebody told me that number for this engine but I don't recall who or if I wrote it down somewhere. I may have to call Marine Power again.