'75 Mercury 1500 stalls on acceleration

[rickdb1boat]

Re: '75 Mercury 1500 stalls on acceleration

Steve,<br />Are you running a 50:1 Mix now. If not , you should be!

 

[sbryant]

Re: '75 Mercury 1500 stalls on acceleration

Hoo boy. I wasn't really expecting any more replies to this... I switched to nothing but 92 octane for the boat last summer after a lenghty discussion under a different thread. I'm running 40:1, sometimes almost 50:1 mixture, because that's what the motor seems to like the best. I tried the 32:1, and the motor wasn't overly happy with it, even when I adjusted the mixture screws (going by the manuals instructions of course.) I have tinkered with the mixture screws on three different times out on the water, just to make sure I have them at the best setting for my motor. At this point, there really is no more hesitation on the way to WOT (except when more grit washes up from the gas tank and plugs the filter, which is why I plan on installing a clear in-line before taking it out on the water this year.) The only real problem I have left is that WOT is only hitting about 3200 RPMS. But, I think that's probably due to the wrecked sparkplug wire mentioned in my last post. I don't think the #4 cylinder has been firing at all with the wire in the condition it is. I plan on replacing all the sparkplug wires before taking her out this year, and hope that will take care of that issue. <br />Thanks again everyone! I have to say, I do a lot of newsgroup and message board browsing, and this is BY FAR the most informative and helpful group I've ever come across.<br /><br />-Steve in Idaho

 

[sbryant]

Re: '75 Mercury 1500 stalls on acceleration

Correction to previous post:<br />After the fixes, I was able to get it to 4100 RPM. (I just checked my notes, 3200 didn't sound right.) My understanding is that the max RPM for this motor is SUPPOSED to be 5200-5500.<br /><br />-Steve in Idaho

 

[Gold Bear]

Re: '75 Mercury 1500 stalls on acceleration

Steve in Idaho <br /> You need to keep after the low RPM's "problem" until you get the engine to operate in the correct range.<br /><br />I would pursue the #4 spark plug wire problem first.<br /><br />If you have never reached the correct range, perhaps you should consider installing a prop with less pitch. There are plenty of threads here that cover that adjustment. If the engine does not turn up enough RPM's it will carbon up, and that in itself will cause it to run poorly.<br /><br />Good Luck,<br /><br />Gold Bear

 

[sbryant]

Re: '75 Mercury 1500 stalls on acceleration

I fully plan to replace the entire sparkplug wire set when spring comes around. The weather here has been... odd. Very spring-like at times, and then this morning, I awoke to snow. Ugh. I'm willing to bet at this point that the #4 cylinder wasn't firing all last summer, and I think that would account for the low RPMs (not to mention the crummy fuel economy I was getting.)<br /><br />Steve in Idaho

 

[Preston]

Re: '75 Mercury 1500 stalls on acceleration

Hey Steve<br /><br />I am currently running a Mercury 1400, the same vintage as your 1500 on a 17' glastron. I have had serious trouble with fouling the plugs and have had to go to a step hotter plug-- (not recommended). I have come to the conclussion that the main jets are too large for the altitude that I am running at, here in Burley, Id. You might check the burn on the top of your pistons and then check your manuel for what it recommends for a correct jet at your given altitude. My manuel noted that many Mercs' had the largest jets installed as a standard application. <br /> I do not recommend messing with changing the ratio of oil to fuel, it should be 50:1 and use a good quality omc approved brand, however; there is extremely good advice to burn the premium fuels with at least 92 octane. Anything of a lesser quality has a poor detination and at best a very short life in the tank before it begins to varnish. I have had people tell me to not let mixed fuels set longer than 30 days. <br /> As for the RPM, check the prop for pitch. I had to drop (2) sizes to get up to the proper 5500 range. Boy what a difference. Come to find out the prop that was on the boat as well as the jets were for down in the Lake Powel area. I'll bet it was a screamer there.<br /> There is one other item you might consider using as it has been recommended several times on this sight, and I can attest to the effectiveness of it---SeaFoam as a fuel additive and stabilizer.<br />Works great!!<br /><br />Preston

 

[waynebo]

Re: '75 Mercury 1500 stalls on acceleration

did'nt read all the post so this may have already been recomended.After tear down on carbs remove the jet with tight fitting screw driver and flush out with any good carb cleaner.once back on motor,now install a good spin-on water/filter seperator.If you dont do this it will run good after you work on it and then go downhill as it clogs up again,sound familar. waynebo

 

[sbryant]

Re: '75 Mercury 1500 stalls on acceleration

Preston, your elevation is 4100 feet or thereabouts, right? Post Falls (where I live), is only at 2200 feet. I don't really think the size of the jets is the problem, though I'll consult the manual just to be sure... Prop will be my next check after I see how it runs with new spark plug wires.<br />Waynebo, I totally rebuilt the carbs over the summer, and plan on putting in a good in-line filter this Spring.<br /><br />Thanks to all!<br /><br />Steve in Idaho