Finally got it wet

[Neverquit]

Took the Starcraft out again today, fishing was slow but we still brought a few home.

Engine was running good and I was expecting to see better performance with the fresh carb, better but still not there.

Was hitting 3500 RPM and 37 MPH on the gps today.

I tried taking off the 14 x 19 prop and put on the 13 x 17 expecting to see higher RPM, No seemed it was only getting just over 3000 RPM and top speed was under 30 MPH so I put the 14 x 19 back on.

It seems to be leveling off fairly good on plane and really it is already going faster than I need but I am still puzzled as to why I am not getting into the mid 4000 RPM range.
It does seem to act a little tail heavy out of the hole.

Weight wise in the back roughly was a trolling motor (25 lbs), 2 batteries (142 lbs), tool box (15 lbs), anchor (20 lbs), tackle box (25 lbs), daughter (100 lbs) so say 327 lbs.

Up front my wife and I, 1 battery, cooler and misc spare parts in storage area for an estimated total of 410 lbs plus a full tank of fuel.

Does this sound reasonable or would shifting some weight around help?

Can anybody with roughly the same boat motor and prop combination share what RPM's and MPH you are getting?

85 Starcraft holiday 18 with OMC 140 engine and 14 x 19 prop.

Trolling it was running smooth as glass pushing along at 3.8 MPH @ 650 RPM.

 

[Alumarine]

If you're getting 37 mph on a gps I'm guessing your tach is reading too low if it's only showing 3500 rpm.

 

[Watermann]

^^^ exactly what I was thinking. Always seen the RPMs being higher than the MPH. Also I've not heard of a 2" drop in pitch loosing 500 RPMs.

 

[Neverquit]

From what little I know and have read about props (which I admit isn't a lot).

Based on "Assuming you have the HP a higher pitch will give you a higher top speed."

To me made sense as to why my top speed was lower with the 13 x 17 prop.

Rpm wise the results made no sense to me either, then I got to thinking;

As per information from previous owner the complete lower leg had been replaced.

As per me finding the wrong seals on the upper which led to the bearing failure I know someone has had it apart before.

Now what I don't know is;
What gears were in the lower leg he purchased.
What gears were now in the upper that I know has been apart.

So I went out to the shop after lunch, put the boat in gear, disabled the ignition, pulled the plugs, marked the prop and started barring over the engine.

It took about 1.7 turns of the engine to get one full turn out of the prop.
Tried it again and just shy of 7 turns of the engine equaled 4 turns of the prop.
1.71:1 ratio.
If I am correct it should be a 1.71:1 ratio for the 4 cylinder unit.

3500 engine RPM is 2047 RPM to the prop shaft.

To me this sounds a little low.

Back to going over the motor again and hopefully something else will show up.

I will also compare the tachometer to a known one at high RPM, this one has been reading consistent to my meter while testing up to around 3000 RPM, I have not compared it at higher RPM's although I do know the tach on the dash will reach 5000 RPM in the test tank no load.

 

[Alumarine]

Don't rev it to 5000 without a load. Especially if your tach is out.
The fact it revs that high without a load doesn't tell you much.
It will do that on 2 cylinders.

 

[Neverquit]

Don't rev it to 5000 without a load. Especially if your tach is out.
The fact it revs that high without a load doesn't tell you much.
It will do that on 2 cylinders.

It has never seen more than a quick blip on the throttle to that RPM which is why I have not been able to compare the tach to my meter, it is difficult to do much in a 300 gal tank, either going to have to load up some test equipment and go do some power tuning on a lake or just keep at it like I have been doing it bit by bit, then I have an excuse to take it out more often until I get it right.
Which is not a bad thing either as my wife and I have already been out more times this year than all of last summer put together.

Darling I set the timing, we need to go testing/fishing again
Darling I;
put a new water pump in
put new bearings and seals in the upper
put a new prop on
rebuilt the carb
fixed the tilt clutch..................

Lots of fun either way

 

[Watermann]

That gear ratio isn't right, my 4.3 L V6 is 1.81 and 3.0L 4s should be 1.94. I don't know of any MC gear sets being 1.71.

 

[Neverquit]

Don't recall where I read it but it stated the overall ratio for the 4 cyl was 1.71:1

I am guessing this takes into account the ratio in the upper case combined with the ratio in the lower leg.

Would be interesting to know if this is wrong as it would help explain my issues.

 

[Alumarine]

That gear ratio isn't right, my 4.3 L V6 is 1.81 and 3.0L 4s should be 1.94. I don't know of any MC gear sets being 1.71.

He has an OMC. I'm not sure what the standard gear ratio's are for those but I'd think 1.71 is a bit high for the 140.

 

[Watermann]

He has an OMC. I'm not sure what the standard gear ratio's are for those but I'd think 1.71 is a bit high for the 140.

Yeah I know it's OMC, I know only MC but the gear set in the upper shouldn't be much different by engine.

 

[Neverquit]

I looked up the part numbers for the upper and lower gear sets for my exact year and model number.

Lower leg takes a 13 tooth drive gear and a 26 tooth driven gear.

Upper gear case takes a 21 tooth drive gear and a 18 tooth driven gear.

Did the math on it and 1.71:1 is the correct gear ratio for this unit.

 

[Watermann]

Are these the same as MC where the gear ratio is set in the upper gear case with all lower gear cases being the same?

 

[Neverquit]

A handful of design changes over the years with many different ratio's available for the upper and for the lower.

Lost track of how many different gear sets you can get for the upper and for the lower.

Upper 20/16, 19/20, 21/19, 21/16, 21/18, 21/20

Lower 23/15, 26/14, 26/13

These are just the ones I have come across while doing some research, probably are more out there than what I have listed.

You could get 18 different combinations just from the above.

From what I can tell there was a different ratio for 4 cyl, 6 cyl and v-8 and every time they changed part of the design they changed to a different ratio gear set upper and lower as well.

 

[Watermann]

That' sounds confusing as all get out :faint2:

 

[Neverquit]

Took the boat out again on Friday, did not change anything but this time I brought along my digital tachometer.

Got my better half in the drivers seat going wide open, dash tach was reading around 3500 RPM, I hooked the other tach on the engine and it was reading 3875 RPM at 37 MPH.

Probably could squeeze a little more out of it if I play with the jets and power valve but for now I am happy with it as is.

Caught a half a dozen fish, had a great shore lunch and enjoyed not having to fix or adjust anything for a change.

 

[Neverquit]

Thursday's fun;

We took the Starcraft to check out to a fairly remote lake, we were the only ones there out all day.

Go to leave only to find a black bear standing smack in the middle the ramp watching us, the noise of the boat was not scaring it off so we decided it would be wise to cruise the lake for another half hour.

Pulling back up to the ramp I was half expecting to find the bear on top of the deck of my truck as I had been hauling salt blocks out to the cows the day before, fortunately it was long gone by the time we returned.

Saturday;
Spent half a day in the boat at home with a laptop finally figuring out how to properly set up the Humminbird helix, manual is near 300 pages long and covers a dozen different models so it was a chore to say the least but it was worth spending the time as I now feel somewhat educated on what half the settings and functions do.

Sunday's fun and follies;

Spent the afternoon on a lake with the whole family aboard, caught some fish, stopped and cooked up dinner on shore.
Boat was working great except for a minor problem with the shift interrupt switch.
Made a minor adjustment and I felt that problem was solved.

We had been anchored and still fishing a ledge that dropped from 18-26 feet and the fishing was good but it was getting late so we started to head back to the ramp.

Engine fired right up, went into gear nice and smooth, throttled up just fine but it was not getting up to speed so my mind went into troubleshooting mode, I was only hitting 16 MPH and not leveling out. What could be wrong now?

Did I screw something up on the shift interrupt switch?
Am I taking on water?
Maybe a fuel restriction?
Is there too many people and gear in the rear of the boat?

It was then that I shut off the boat and while trying not to laugh too hard I sent one our son's up on the bow and to pull in the 20 lb anchor.

Me being the one that is always preaching to double and triple check everything somehow skipped a step and I am sure it will be years before the boys stop rubbing it in.

 

[ShoestringMariner]

I think we’ve all done that once

how is do you like the Helix?
its on my shopping list

 

[Neverquit]

Like I said it takes a while to figure out all the features on it, but once you get past that you will be happy.

The more features you want the more it will cost you.

I really like the GPS feature, it gives you an accurate speedometer and will bring you right where you want to go which I find handy when on a new to me lake or in bad weather, fog, dark etc.

I even got out of the truck once, hopped in the boat and turned it on to figure out where on a remote road I was.

 

[bchaney]

Glad you are enjoying the boat, that sounds like a great weekend. At least a dragging anchor is an easy problem to fix.

 

[Watermann]

Many a boat has been lost due to anchor dragging and winding the line up around the prop, a snagged anchor with the prop being a windless will sink a boat quick. Glad that it drug along and that didn't happen.