Fuel ecomony

[TMALEGA]

I was just wondering how much fuel economey is hurt or changed due to a bad prop. I ran about 1.5 hours on 6 gallons and it wasnt at wot the whole time. I would have put this in the prop talk but i thought if it isnt prop causing it then it may be a engine issue and you would be the ones to ask on it.

One other thing how does one calibrate a tach? I have it set to 10p and it is showing too high a reading, i did try to switch to the other acc post on the rectifier last night and havent been able to restart it to test it.

All this is on a 1985 85 hp force motor. I was told i should be able to run the whole weekend and still have a little gas left over on a 12 gallon set up.

Thanks for listening to my bordem at work and questions i have.

 

[ezmobee]

Re: Fuel ecomony

Following the very general rule, your motor should burn around 8.5 gallons per hour at WOT. So that certainly isn't a whole weekend on 12 gallons unless you're hanging out at the sandbar all day.

 

[TMALEGA]

Re: Fuel ecomony

Ok i wasnt sure how much the prop being bent and dinged up was affecting the econemy. Any ideas on how to cal the tach?

 

[jerryjerry05]

Re: Fuel ecomony

Untill the tach is working right.And we know the RPMs at WOT.And what pitch the prop is.
These all factor in economy and performance.With out a working tach.We'd be using the WAG system(wild a## guess).J

 

[TMALEGA]

Re: Fuel ecomony

This i understand that is why i was wondering how to cal the tach.

 

[jerryjerry05]

Re: Fuel ecomony



On the back of the tach is a small slot that takes a knife point or very small screwey.
Turn it one click at a time while the motor is running.This should make it run right.
If it doesn't then you probably have the wrong tach.
Make sure the tach is wired right.J

 

[TMALEGA]

Re: Fuel ecomony

ok thank you jerry i have that set to a 10p i was told that was where i needed it to be. is that incorrect? i have 4,8,10 and 12 also all of which have a p after that. i also have this tiny little hole on the oposite side that has cal. above it and it takes a very small scew driver and has what i guess is a screw of some sort. i cant get a good enough picture to show you what i am speaking about. i will go see if there is a model number on the back of the tach. i saw no model number however here is a pic please excuse the mess of wires it isnt as bad as it looks.

 

[Frank Acampora]

Re: Fuel ecomony

The calibrating potentiometer is only good for a couple of hundred RPM maximum, so don't bother messing with it.

The "P" stands for PULSES. While the 20 pole alternator does have 10 poles dedicated for the charging circuit, it does not output 10 pulses per rev, rather a larger AC fluctuating voltage because of the number of magnetic poles in the strip magnet at the flywheel rim. Because you are taking an AC signal, it doesn't matter which AC terminal on the rectifier you connect to the tach.
More than likely you have an incorrect tach. The only tachs I have seen for 20 pole alternators that were adjustable for 12 and 20 had a 3 and a 4 setting on the back.

I don't know if they still make them, but Teleflex made the sportsman or international series (I think red) in 0-6000 for 12 pole and 0-8000 in 20 pole

 

[SwampThing]

Re: Fuel ecomony

Just how "bent and dinged up" is that prop? I would be more concerned about a "bad" prop destroying a bearing or something else than about fuel economy.

 

[TMALEGA]

Re: Fuel ecomony

I have taken the prop by a repair facility trying to get a match to it but he told me it isnt damaged enough to cause wear to anything just enough to cause power and fuel problems. I have no vibrations in anything at any time, as for the tach i will take this one out and take it back and see about getting one that is like you described thanks for the advice. I may just buy one from ebay and call it good i just wasnt wanting to get a high dollar tach when i wasnt sure the tach was frozen in place. Now that i know it at least works i may just get one and call it good.

 

[zubol]

Re: Fuel ecomony

also try tach made by Faria. I bought this one: http://greatlakesskipper.com/produc...-outboard-only-oversized-boat-tachometer.html

 

[steveclv]

Re: Fuel ecomony

also try tach made by Faria. I bought this one: http://greatlakesskipper.com/produc...-outboard-only-oversized-boat-tachometer.html

For $39 - someone grab them quick!!

 

[TMALEGA]

Re: Fuel ecomony

So i would get one of those but the shipping to my door is 20 bucks and i can get the same thing from the same supplier on ebay for 5 bucks more with free shipping. However i am leaning towards the white face one since my volt meter is a white face gauge. And it is 65 i think with free shipping.

 

[SwampThing]

Re: Fuel ecomony

I have taken the prop by a repair facility trying to get a match to it but he told me it isnt damaged enough to cause wear to anything just enough to cause power and fuel problems. I have no vibrations in anything at any time, as for the tach i will take this one out and take it back and see about getting one that is like you described thanks for the advice. I may just buy one from ebay and call it good i just wasnt wanting to get a high dollar tach when i wasnt sure the tach was frozen in place. Now that i know it at least works i may just get one and call it good.

I don't want to sound condescending but what does he base this on then? How can the prop be damaged to a point that it will cause "power and fuel problems" and yet not run the risk of further engine damage? It's your boat and your engine do what you want. Of course it could be that it's not damaged enough to cause either problem. Admittedly, I ran a damaged prop for a season with out any issues also. I only brought up the prop issue in the first place to possibly save you additional grief further down the road. If you think it's good then run it. Just be aware.

 

[TMALEGA]

Re: Fuel ecomony

Now i understand your worry and statement, which is why i am taking it in to get repaired this week hopefully. His explination was that it isnt causing a vibration and is not bent any more then a normal force prop but it is missing parts of the ends from where something hit it. So what he was explaining to me was that it was in need of repair but the engine would have to use more fuel to get going and continue at a given speed but since there was no abnormal vibrations as he put it then i should be ok until i got a working tach going. My plan is to repair this one and get another for my main and keep the old one as a spare. Thanks for the advice and i didnt take it as anymore then good advice.

 

[jerryjerry05]

Re: Fuel ecomony

Whats "not bent any more then a normal force prop" mean???? ANY bending and chunks missing can cause damage to the shaft and bearings.
If anyone tells you it's ok to run with a bent /broken/twisted any kind of damage prop.I might wonder about that.Post a pic before you repair.I'd like to see it.J

 

[TMALEGA]

Re: Fuel ecomony

Will do jerry tonight when i get home i will post a few pics for you guys. From what he was telling me, force props come with a cupped edge. So he said it was not any worse then they come in it is just missing pieces. I have seen worse.

 

[TMALEGA]

Re: Fuel ecomony

So i took the prop to a prop rebuilder and seller and he laughed when i told him what the other store had told me. Apparently they have a bad rep and i had no idea of this but do now. First question he asked was if i was sucking the gas straight out of the tank and having to get right back on the trailor to fill up. Second was if i was even remotely getting any power out of my motor. Both of which are issues i have had obviously. But i should have my rebuilt prop on friday of next week. Said i will think it is a whole new prop when he is done with it. So here are the pics i promised they arent the best but does show some of the damage. If he cant fix it then the only prop he has for it is a 17 pitch not a 19 but it is all that is in the city. New wise.

 

[ezmobee]

Re: Fuel ecomony

Yeah that one was pretty bad. I could see that costing you some power.

 

[TMALEGA]

Re: Fuel ecomony

so to post a update i got my old damaged prop back from the repair shop today. i also got a used one from the same guy for 50 bucks it is a 19 pitch also but it is going to be my back up the one i had repaired is going to be my primary. here is a pic of the repair i think it turned out really well.