What kinds of engine instruments are on your boat?

[ThePHNX]

Do any of you - given the lack of information from engine manufacturers like Mercury - add things like vacuum, manifold pressure or fuel flow gages to enable better power management?

While many like to talk speed, my interest is range: both are served by knowing proper power settings.

HBH

[1bayouboy]

I have a 350MAG MPI engine that I added the smartcraft system tach and speedo with the system link gauges .....I don't think you can get any better info. It's good enough to sway me towards the optimax for repowering my Tsunami.

[Bigshrimpin]

Phnx - If you're interested in Range, repower with the Diesel cummins/mercruiser 1.7L 120hp combo. The package is around 10K (sometimes under)

http://www.cmdmarine.com/PDFs/4081824_1104.pdf

Lots of folks here have fuel flow gauges, but I doubt many people monitor there motors past the usual Temp, water pressure, and oil pressure (i/o). The ammount of work/time it takes to fine tune your rig and get the extra mph or gallon per hour just isn't worth it to most folks. You might be able to find a machine shop that specializes in rebuilding marine motors to help you, but I beleive that most folks with your motor just want to go fishing or cruising.

[spareparts]

a vacuum guage is a complete waste of space on a boat, the only time it will ever read vacuum is when your idleing, or when you back off the throttle, you're under enough load the rest of the time, that a vacuum guage will read very little difference, if any, when plumbed to manifold vacuum. Best guage to get is a reliable tach, and check it against an even more reliable tach, check all you guages at normanl operating range against known measuring devices. Most marine gauges read somewher close, never accurate. I've check 6 new temp gauges right out of a box, found them to be as far as 25 degress off, no two of them were the same. Buy a good fuel flow meter and calibrate it, they are close sometimes, but whats the use if you don't know if its right. Be carefull with the smart craft, that is a calculated fuel flow, not a measured fuel flow, and the fuel level is only as accurate as who calibrated the smartcraft when it was installed

[Miles Offshore]

i use and calibrated my fuel flow gage(navman)and love the thing. I have friends (hard to believe I know) that never even put fuel gages back in their boats when replacing tanks or their gages go bad. The standard fuel gages are notoriously innacurate. When you calibrate one though, I think it is neccesary if you have a fairly large tank- i.e.> 25 gallons, to calibrate it using the largest amount of gas/number as possible (gallons at refill vrs stated # on meter). Trim Gage would also be nice- (trim Tabs)- i have seen the smartpack system on my buds new 350/325 merc i/o/ coupled with the garmin bottom machine and it is sweet. I like to track engine hours as well for oil changes, thats about all I pay close attention too- The navman/tach/motor water temp (and charging system and track of the boat while running set-up on the plotter)

[ThePHNX]

More good input, thanks Spares.

Was wondering if engine instrument displays couldn't be brought into the Garmin network capable plotters such as the 3006C.

Would need something more than the transducers/senders, a black box to translate the information to display. Know of anything? Will check with Garmin.
On the instrument errors: can most these be calibrated and are there services that will calibrate them to a standard reference?
The RPMS you guys talk are very high to me, 5,000 plus - more like two stroke motorcycle turns. Am I hearing two-stroke RPMs or are you also running the 4-stroke GM engines that high on a constant?
I do note that the lower ends are beefed up - more mains - over their automotive brethren.
What RPMs are best for cruise on plane with the stock I-6?

Thanks, HBH

[spareparts]

the mercruiser smart craft is NEMA 183 compatable, Navman and North Star GPS( Brunswick did own them, i think they just got sold off) are plug ins to the smartcraft systems. Volvo has had the same on their diesels for about 5 years. Most every one in the market is now offering NEMA in/outs for displays. I hooked a Bennet trim tab indicator( NEMA 2000) to a RayMarine E-120 last week, i'd rather have separte gauges personally, but it worked like it said it would.

Recomended max rpms for current MPI Mercuiser 4.3, 5.0,5.7, 6.2 engines is 4800-5200. Older engines( pre vortec head motors) were 4400 to 4800( most people proped the 5.7 out to 5000, they feel good there). Your 250 six needs to turn 4400 max( light loaded), ahd a friend that hot rodded his, he turned it 6500 with stock bottom end, never had a bottom end problem. I don't know why, but allmost every engine combo i have monitered for fuel burn, seemed to like 3000 to 3200 for best fuel burn to speed, it didn't matter if it was 4 cyl, or 500 hp v8( it depends on which hull as well)

[1bayouboy]

Ditto that Spareparts....my 5.7 Horizon is spec'ed at 4800-5200. I propped it to turn 5000; but I cruise around 3600-3800. Best fuel efficiency is in the 3000 range. I believe the Horizons all have roller lifters.

[ThePHNX]

Terrific Info.
The 3000~3200 comes quite close to that `magic' 75% setting.
BTW: spent some time thinking about it and have to disagree with you on the vacuum gauge. Manifold pressure and vacuum tell a great deal about load and efficiency on normally aspirated Internal Combustion Engines. Suspect you have used a shop gauge to diagnose engines, the common panel gauges are colour coded to show most efficient, moderate overloading and heavy overloading. A few of the high performance cars I've had came with vacuum gauges straight from the factory - think it was a mercedes that described it as a better shift indicator than simple RPM. Several machines have had `shift lights' that were the vacuum equivalent of an idiot light. The value of the gauge is somewhat diminished by the skill of the user. In hands like yours, I'll bet you can spot a burnt or sticking valve, ot other combustion problems with one.

You are right that it is not an instrument for constant reference, but I can see smoothing out acceleration and getting up on step by keeping it `in the green'.

Am thinking that if we do install one it might just as well go on the engine housing facing the console rather than run tubing hither and yon. Is there a vacuum sampling port on the Merc's?

Back to your excellent info on instrumentation. As you pointed out previously a fuel flow reading that is computed rather than actually measured is less desirable than a true flow measurement. What units in your experience actually give true readings rather than estimated?

Did you also ever see my question as to instrument calibration services?

Thanks, HBH

[Bigshrimpin]

I've had two navmans (F2100 and older F41?? model) on different boats and they were dead on out of the box.