Runnin a merc 40:1

[andy6374]

Can you do any damage running the engine 40:1 versus 50:1. The mechanic i bought my 88' V6 200hp merc carberated off (as a side note he is a great mechanic, always helps me for free and gives me parts) told me too. He rebuilt it and says he always runs his engines 40:1 and they never burn out or lose compression. They only side effect I can see so far is that you have to replace the plugs more frequent. I probably loose rmp's as well. But is there anything else to be concerned with.

 

[ZmOz]

Re: Runnin a merc 40:1

No...that's fine. I run my inline 6 at 32:1. (actually rignt now it's 25:1 for break in) You'll get a tad more smoke and might make the plugs a tad dirtier...but it will hardly be noticeable. It is very good insurance.

 

[andy6374]

Re: Runnin a merc 40:1

My old 89' V6 200hp Black Max Oil injected, which burnt out (oil injectors failed, horribly!), pushed my boat 36 kts. My rebuilt 88' only gets 29kts. Could the higher oil to fuel ratio explain the decrease in max speed.

 

[JB]

Re: Runnin a merc 40:1

Using 40:1 rather than 50:1 should have no effect on top speed, andy. <br /><br />It probably will make more smoke and shorten time to clean and gap plugs and to decarb, but it shouldn't affect performance at all.<br /><br />Good luck.

 

[LubeDude]

Re: Runnin a merc 40:1

Originally posted by ZmOz:<br /> It is very good insurance.

I believe that the earlier inlines may benifit by running slightly higher ratios, but I see no need to run the v6s at anything other than 50:1. I dont think it will do anything but empty your pockets quicker.

 

[ZmOz]

Re: Runnin a merc 40:1

Originally posted by LubeDude:<br />I believe that the earlier inlines may benifit by running slightly higher ratios, but I see no need to run the v6s at anything other than 50:1. I dont think it will do anything but empty your pockets quicker. [/QB]

It's good to try for 40:1 rather than 50:1 in case you get some bad oil, or miscalculate your oil mix. The difference in cost and carbon buildup is almost nothing...I think it's definately worth it for the insurance. It's also very good in motors with alot of hours on them, since all the clearances are much more loose...the same way thicker oil is better in cars with high mileage.

 

[andy6374]

Re: Runnin a merc 40:1

Then... are there any suggestions why this motor doesn't push me as fast.

 

[timmathis]

Re: Runnin a merc 40:1

Well actually Andy the more oil you put in decreases the octane rating. Witch in turn would lower your performance slightly. I don't think it would that noticeable unless you were timing thru the 1/4 mile ET. from 36 mph to 29 No way it would make that much difference. Is this with the same prop as before? if not that it could be in the tuning! Have you ran a compression test?

 

[andy6374]

Re: Runnin a merc 40:1

Same prop. What do you mean by tuning, I always put in new plugs. Could it be a timing issue? I have not ran a compression test. The guy just rebuilt the engine two years ago and he is the best (next to you guys of course). I would hate to think it has bad compression.

 

[andy6374]

Re: Runnin a merc 40:1

I am going to repost, since we are on a new topic.

 

[Scali]

Re: Runnin a merc 40:1

I started running pre mix @ 100-1 on top of my oil injection this season on my 1994 Merc 40 as an insurance thing.<br />I put 50 hours on it so far & I notice a little more smoke @ start up but thats about it, I think it runs smoother.<br />I do reccommend decarbing more often though, I do it every 25 hours { 1/2 can of power tune & I can REALLY tell the difference afterwards..

 

[andy6374]

Re: Runnin a merc 40:1

When people say decarbing, do they mean take the carbs off and clean them? Becauase that is crazy to do every 25 hrs.

 

[Scali]

Re: Runnin a merc 40:1

no, you spay the aersol crap in the carbs while running then blow it out, that & seafoam ytpe gas additive

 

[andy6374]

Re: Runnin a merc 40:1

Does this clean the carbs. Or does it reduce carbon build up in the cylinders and hence the name decarb.

 

[ZmOz]

Re: Runnin a merc 40:1

It removes the carbon buildup.

 

[andy6374]

Re: Runnin a merc 40:1

Is there a preferred brand of decarb stuff. I have heard mixed reviews on Seafoam.

 

[ZmOz]

Re: Runnin a merc 40:1

Anybody who says something bad about Seafoam has never used it.

 

[dajohnson53]

Re: Runnin a merc 40:1

Andy6374 - read the FAQ on decarbing. There are two methods of doing it - the spray in the carburetor method and the tank method. You can also routinely add some to the gas as a preventative.

 

[andy6374]

Re: Runnin a merc 40:1

Thanks everybody, I decarbed today with some Power Tune. Lots of black crap came out my exhaust. Engine is running great. But my engine still isn't pushing me as fast as it should (34-36 kts), it is about 7-8kts slower than it should be.<br /><br />I will report back with a compression test and max RPM.

 

[timmathis]

Re: Runnin a merc 40:1

Yes Andy I did mean timing. That is part of your tune up I would Do a Link & sync on it. That may put you where you want to be in MPH. If that motor has it in it. You can take 2 motors of the same year and size and they may vary in speed! That could be due to the internal balancing compression etc. Tim