Any outboard motor mechanics?

Sorry for not coming back earlier, my O2 card was not working on board where I was from Friday.

All these comments are aplicable to simple carbed motoes

Firstly all marine engines are not tuned for optimum performance (and by the bye do not run at their best out of the box) but often for worst scenario, poor fuel poor operating conditions, requirement for longevity ect. My comments about "secret" were flippant I know that many people know how to do it.

Simply dynamically tune the thing under the operating conditions it is normally run.
You may be surprised at what you can get sometimes just by using differing plug configurations over gapping the plugs and a slight advance in ignition timing.

We used to do it by blueprinting i.e. selecting the best tolerance parts and building from there. Modern engines are made to such close and constant tolerances that unless it is for out and out racing that is now pointless.

As for what I base my comments on that's from 30+ years of doing it.

David
 
David,

I'll certainly second your comments about engines not giving their best "out of the box". I've got two Mariners and one had to be taken back (twice) when new. The dealer should have checked it over properly but it must have been a "Friday" engine; in the end it was exchanged for another new one.

I would also agree with your comments about tuning engines to get the best performance out of them. In my motorcycling days we would go to enormous lengths to get a tiny bit more out of an engine. I must admit that I don't bother these days with outboards. Perhaps I should, but I'm more interested in them starting easily and running reliably.

From your earlier postings my guess is that you are mainly involved with bigger (inboard?) installations, rather than small outboards. However this thread started with a question about restrictor plates on small Suzuki's, and I am going to try to get you to concede that in some cases it really is as simple as removing the restrictor plate. Obviously not in every case and presumably not in the case of big high performance engines; but quite common at the small end of the business.

Go on, admit that we are right! /forums/images/graemlins/smile.gif

Joe
 
Outboards, along with most other things, cost us what the manufacturer thinks we will pay, and may have little to do with what it costs him. Examples are the variations in price between here and the US, and until recently cars here and on the continent. I heard a rumour that 4-speed Vauxhalls used to be 5-speed with a plate to blank off 5th gear, yet cost a couple of hundred quid less!
 
"I am going to try to get you to concede that in some cases it really is as simple as removing the restrictor plate", No need, (I already said it in the first sentence of my first post on this subject). I really can't see how it could be clearer.

"Go on, admit that we are right!" Read my post I said it can be that simple but often not.

You are correct in your assumption about larger inboards, at least these days. But and guess I may be guilty of considering any O/B below a 40 small.

I guess I could have said it might work and it might not like everybody else, but I thought a little more detail might help in pointing the original questioner in he right direction if it did not. I stand by the technical content of my posts on this subject though I certainly will not trouble myself in future.

David
 
Thanks for clarifying that, David.

I do hope that you do "trouble yourself" in future. Most contributors on this forum appreciate the helpful advice that comes from many quarters; the trouble is that frequently the advice is different. It can be hard to sort the wheat from the chaff. On this occasion I think we were both trying to help the original poster, but probably coming at it from different directions!

Joe
 
There are regulations over here with regard to operating a boat with more than 10hp, hence all the 9.8, 9.9, etc. models. Most boats have max. hp ratings. One of my dingys is reg'd at 12.5hp, another at 3.5hp. In order to fit all the different criteria manufacturers de-rate their motors with restrictor plates. My 9.9 Mercury is actually a de-rated 15hp. It is very common over here for mechanics to take the five minutes to up the power of a 9.9hp to 15hp for customers who want the extra ponies but need to remain compliant with the below 10hp stickers on the motor.
 
Now that _is_ interesting.

I have the 10HP Mariner Magnum. Is this easily re rated to 15HP? I use it as an aux but have been knonw to hoon with it on the tender too:-)

Mind you, in a fit of pique last month I managed to pull the choke knob out, indeed right out of the motor. Nowt seems broken, any idea how it goes back?
 
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