motor de-carb treatment...

[Deiter]

gday gents, wondering if anybody out there has used a de-carb treatment of any description on their donks.

I have heard about "sea-foam" and some others (redex, i think?) being used by mariners who say the difference in performance from before and after can be huge.

Now, just recently i had someone more learned than me in these things telling me that sometimes these treatments can have disastrous effects, depending on the condition of the motor.

anyone more enlightened on this topic, your knowledge would be greatly appreciated.

deiter

[Big_unit]

Any power tune / de carb solution is detrimental to any old motor that is beyond repair due to being worn out. Its because the carbon build up behind the rings holds them inplace then you remove the carbon, and thats when you lose compression and risk blow by condition. This mainly applies to four strokes.

Two strokes will also behave poorly for similiar reasons but due to loss of compression in the crankcase as this is where the carburretted two stroke relies on the engine getting the fuel / air mix down the transfer port into the combustion chamber. End result is obvious losses in power.

DFI two strokes are a slighty different story.

Cheers
James

[Deiter]

thanx James, i am not a marine mechanic, but i understand what you are saying - don't do it.

appreciate the feedback

deiter

[QldKev]

I tried it out for the first time about 1 year ago. Engine was a 1977 55hp Evinrude I had for 6 years. I used the 'Johnson Engine tune up'. To say a lot of smoke and bits of carbon were removed would be an understatement. Afterwards noticed it cranked a lot faster, felt smoother, and had a better top end speed.

As soon as I got my next boat 1977 Merc 85hp, I performed the same treatment, and once again happy with the outcome.

A few things to think about;
- carbon is course so it can easily damage an engine, to me its better of not in there, causing premature wear.
- if you mainly do high speed running carbon will not be as much an issue, as a troller.
- carbon can help with comperssion in a really bad engine, but chances are this engine is almost ready for a rebuild anyway, so yes a decarbon may stuff a working engine. I personally have never seen it happen.

Hope this helps

Kev

[flotsom]

big unit is 100% correct.

[Deiter]

ok, so from the feedback so far, am i correct in saying that if your motor is nearly stuffed, a de-carb will finish the job.

but what effects/benefits may one expect from a donk that is still in reasonable running condition.

i have a '91 model johnson 90hp that is clean as a whistle under the cowl and revs well (wot = 5600rpm @ 35kn on 17ft glass runabout, unsure of prop size). i have owned it for about 18 months, no probs, just likes a fair bit fuel to start.

so enough beating around the bush, here's a direct question - if this was YOUR motor, with the knowledge and experience YOU have, would YOU give it a de-carb treatment, or just leave it the way it is.

thanx to you guys who have offered your expertise/ opinions so far.

Damo

[MyEscape]

Well you mentioned that it runs well and plenty of revs etc. "just likes a fair bit of fuel to start"

That has to be a different problem. Hot or cold starts?

Is it really getting fuel when you prime it to start with. My 2 bob's worth only, but perhaps the problem might be with the fuel.

Steve

[Big_unit]

Deiter,
Take it to your mechanic and have him look over it. If you both feel confident that a power tune will be solve the problem then do it. There are a a range of problems that could be causing the start up issue.

In short to answer your question - Yes taking into account that its been regularly maintained & isnt worn out.

Cheers
James

PS - I am not a marine mechanic either.

[BaysideMarine]

Go ahead Deiter, it will be fine.

I had a 200 Evinrude 78 model a while back that came in slightly down in comp on one cylinder. A quick hit with the power tune followed the next day by a hard full throttle run and the comp was back up with the rest of them.

Its a great product and should be done every season or 2 to keep carbon buildup down.

Cheers,

Nicholas