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-   -   My new outboard (http://www.rib.net/forum/f36/my-new-outboard-30236.html)

Steve Waters 02 June 2009 04:13

My new outboard
 
Hi eveyone, at long last I managed to get out on the water. Spent a couple of hours out on the Solent yesterday brilliant weather and a fantastic feeling after not Ribbing for so long. It was the first run for my new 50hp Honda outboard and it performed as expected, very nice. The only thing we were worried about was that the rev counter showed bordering on the red at about three quarters throttle and if I opened her right up it vanished out the other side of the red to the needle stop. I wondered whether I have been given the wrong gauge or whether a bigger prop is needed, it is on an Avon Searider 4m any suggestions?
Great to see some others out there as well with lots of cheery waving! and we avoided every sand bank we saw, quite an achievment!!:)

Poly 02 June 2009 05:16

Steve,

The gurus will be able to advise more specifically if you can tell them:

(1) the actual RPM shown on the gauge.
(2) the recommended max RPM for the engine (in the manual).
(3) the pitch of the prop you currently have on.
(4) the speed you were doing (and how measured e.g. GPS).

the bandit 02 June 2009 15:12

Your rev counter may not be calibrated for that engine. We had a similar but opposite thing happen on our inboard engines hit 69 mph and the rev counters only red 3500 as we were running the engines in little did we know they were actually running at 4800

Steve Waters 02 June 2009 16:17

Ooops
 
Looks like this might be difficult I do not know any speeds as we don't have anything fitted yet that will gauge speed. I also haven't got a clue about prop pitch I'll take some pictures and see what you think. Thanks Polwart and The Bandit for your replies hopefully more to follow!
Steve

Hightower 02 June 2009 17:10

What was the RPM on tickover? It should give you a good Idea on whether the rev gauge is setup correctly or not. Engine should tickover at about 650 RPM as a guess.

Yes and Prop pitch. Should be marked on the prop either as a pitch or a serial number.

Any of the Searider gang will tell you what size of prop you should have for a 50hp motor on the back of a 4m.

Nos4r2 02 June 2009 17:16

Quote:

Originally Posted by Hightower (Post 297714)
Any of the Searider gang will tell you what size of prop you should have for a 50hp motor on the back of a 4m.

Well, maybe-though very few use Hondas.

Hightower 02 June 2009 17:35

Quote:

Originally Posted by Nos4r2 (Post 297715)
Well, maybe-though very few use Hondas.

Have they a wildly different gear ratio then or is it the weight and the fact it's a 4 stroke that will make it difficult to predict what sized prop would be best?

Nos4r2 02 June 2009 17:54

Quote:

Originally Posted by Hightower (Post 297718)
Have they a wildly different gear ratio then or is it the weight and the fact it's a 4 stroke that will make it difficult to predict what sized prop would be best?

Recommended WOT rpm varies,as do gear ratios and weight and so on.It can make a hell of a difference.

Steve Waters 03 June 2009 02:33

2 Attachment(s)
The pitch shown on the prop is 286x330 picture enclosed of the prop and the gauge. I'll run the engine up in a minute and warm it to see what the gauge says at tickover. I put another Honda on because I was so pleased with the 30 I had, although I have to admit I was concerned about the weight when we fitted it! With the flooding hull the RIB sinks down very low at the back until the hull is clear then she planes fine. I think we might move the fuel tank to the front to try and distribute the weight a bit more evenly.
Steve

DonMacN 04 June 2009 12:06

I've just fitted a Honda BF90 to my RIB, with what looks like exactly the same tacho/gauge.

What I didn't know (while running in the engine - just as bandit said above) was that the tacho needs to be matched to the engine - something to do with alternator 'poles' which I don't properly understand. Because of complications with prop pitches, this step was omitted during the original installation.

Maybe you know this, or have done it?? But anyway - on the back of the tacho, if it is the same as mine, is a selectable, arrow-shaped 'switch'. You press it in gently with a small screwdriver and turn it to the right setting, which depends upon the engine, but your dealer should be able to get the right setting from Honda for you.

I found my engine was registering something like 250rpm on idle, when Honda said it wouldn't run at that, and ought to have been something like 750/800rpm. While running at what registered on the gauge as about 2500rpm, I'm sure the engine was probably doing something like 5500/6000!

I got the right setting, adjusted the pot, and all seems fine now. Idles about an indicated 850, runs up to between 5500 and 6000 at WOT depending upon load.


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