engine consuming way too much gas

[Mercs and such]

I took my boat for a unofficial trial run and the 1984 75hp seems to slurp down gas. I have a 6.5 gallon plastic tank and it was gone after about 1hr of running.

Hull is clean
prop is good

i believe it is something to do with the carbs or fuel.

It would also not accelerate instantly. IF i throttled up, it would bog down but if i waited and eased the throttle up, i could get up to WOT.

What could be the problem?

Mercs

 

[Silvertip]

Re: engine consuming way too much gas

It is actually running quite efficiently. A 75 HP two stroke will burn 7.5 gallons of fuel per hour at wide open throttle. Yes - I know you didn't run wide open all the time but if you ran a between 1/2 and 2/3 throttle it would burn between 5 and 6 gallons/hr. It is spot on for fuel economy. How do I know this? I have one and it is fitted with a fuel flow monitor.

 

[Mercs and such]

Re: engine consuming way too much gas

Really? I used to get about 2 hours out of a 6 gallon tank i just had it rebuild. is there a way that it is set too ric. I did notice the plugs are very wet and seem to be fouling. Why is it doing that throttle hesitating??? any suggestions

mercs

 

[saumon]

Re: engine consuming way too much gas

Is it the same engine than the one on your other thread?

http://forums.iboats.com/showthread.php?t=376248

If so, does it have been fixed by you (you mention ?rebuilt?)? And did you wait for your manual?

Sounds like a carb related problem to me. Did you do it yourself to specs?

 

[sschefer]

Re: engine consuming way too much gas

Mercs and Such - You might try just adding info to your current threads as you go. This will keep the history of your work together so we can reference what you've done and give you better answers.

And for Saumon - could you translate this

...If so, does it have been fixed by you

Just pokin a little fun at ya...

 

[trendsetter240]

Re: engine consuming way too much gas

Really? I used to get about 2 hours out of a 6 gallon tank i just had it rebuild. is there a way that it is set too ric. I did notice the plugs are very wet and seem to be fouling. Why is it doing that throttle hesitating??? any suggestions

mercs

The hesitation is likely a fuel restriction or carburetor problem. The carbureters should be removed and cleaned. Next item to check is spark on all cylinders. I'm assuming you checked the compression and it's good?

By the way, if the engine was just rebuilt you should not be running it at WOT until you have completed the break in procedure which takes 10-20 hours of runtime.

 

[achris]

Re: engine consuming way too much gas

Hi Mercs,

Your hesitation is a sign that the carbs are set too lean at idle... Turn the idle mixture screws 1/4 turn anti-clockwise. That will fix the hesitation problem. When you pulled the carbs, did you reset the float levels, as per the Merc manual?

When you say "gone in about an hour", what engine speed were you running at? Also, this rebuild... exactly what was done? Pistons, ring, bearings? Anything else?

Chris.....

 

[saumon]

Re: engine consuming way too much gas

And for Saumon - could you translate this

...If so, does it have been fixed by you


Just pokin a little fun at ya...

Yeah, sure: ?l'as-tu r?par? toi-m?me?? haha! or ?did you fixed it yourself? is it better?

Sorry but sometimes my french to english brain translator is misfring. I dunno if it's the swithbox or the coils, i haven't swapped them yet. I'm no longer under warranty

 

[achris]

Re: engine consuming way too much gas

...

Sorry but sometimes my french to english brain translator is misfring. I dunno if it's the swithbox or the coils, i haven't swapped them yet. I'm no longer under warranty

Well said, sir.... Shame on you, sschefer...


.

 

[j_martin]

Re: engine consuming way too much gas

Yeah, sure: ?l'as-tu r?par? toi-m?me?? haha! or ?did you fixed it yourself? is it better?

Sorry but sometimes my french to english brain translator is misfring. I dunno if it's the swithbox or the coils, i haven't swapped them yet. I'm no longer under warranty

touch?

 

[backyard mechanic]

Re: engine consuming way too much gas

Float levels... there is a float drop adjustment and a float stop adjustment. You are almost certain to find the problem there. Countless times I've found the float levels are off. That spring in the top of the float has an adjustment too. Consult your manual for set up specs and while you're at it... do a sync and link to make sure your timing is right on.

As always check that compression while you are looking at the float levels.