Mercury 2005 60 HP EFI/prop? warning bleep/over-revving?

[Max...]

Had the first trip out yesterday in the 4.7 SR with the above engine. Sea was slight. All well but a few times at the end (only out an hour or so) when I was pushing it a bit more the alarm went off; continous bleep - which according to manual points to over rev, cooling or oil prob. Oil level was fine, tell tale was flowing so pretty sure it was the revs.

Also when turning with power on it seemed to rev-up erratically a bit sometimes.

In the excitement of first trip, nervous family (incl 1 x queasy kid/pushed for time etc) I was not really able to try different secnarios to see exactly when it happened or check revs etc.

I'm not sure I had the trim set correctly if this has a factor but the engine was not excessively up.

Prop on there is a 10.5 x 11 which previous owner had on for watersports. The other prop I have is a 10.5 x 14.

Would welcome any advice on this from those who know these engines or can advise on prop etc.

[SeaSkills]

Max, if it was me (bearing in mind that I know next to nothing about how engines work - someone more knowledgeable will add their comments, I just like to keep engines going!), I'd get it checked out.

The presence of the tell-tale only tells you that the impellor is working and lifting cooling water from the sea. If the thermostat isn't opening, that water won't be making it around the engine and you could still have a problem.

You could still have an oil pressure or valve problem even though the oil level looks right. If your engine was losing power when the alarm sounded, that's another indication of a problem.

Hope ita ll turns out OK

[Poly]

Originally Posted by Max...

Had the first trip out yesterday in the 4.7 SR with the above engine. Sea was slight. All well but a few times at the end (only out an hour or so) when I was pushing it a bit more the alarm went off; continous bleep - which according to manual points to over rev, cooling or oil prob. Oil level was fine, tell tale was flowing so pretty sure it was the revs.

I'd agree with SeaSkills - don't assume that because the oil level is OK and the tell tale is working that there are no other oil/cooling issues it is alerting you to.

Also when turning with power on it seemed to rev-up erratically a bit sometimes.

I'm not sure I had the trim set correctly if this has a factor but the engine was not excessively up.

It sounds like the prop is ventilating (getting too close the surface sucking in air, which is much easier to "chew" so it spins faster). Its maybe a shame that a RIB wasn't available during your PB2 - the instructor would have covered trimming in for high speed turns. Not sure if that would have been covered on the "big boat" or certainly been as obvious, as you are not usually trying to turn through 180 degrees at high speed on a cruiser. Would still have expected them to cover trim settings though?

Prop on there is a 10.5 x 11 which previous owner had on for watersports. The other prop I have is a 10.5 x 14.

The 11" pitch does sound a bit small? Someone who's had a similar combo will be able to comment better - do you have a tacho (rev counter)? do you know what speed you were doing?

[Downhilldai]

I reckon you need a 13" pitch prop on that boat/motor combo.

It will, in all likelihood, over-rev with a 11" pitch. what rpm were you running at when the alarm bell started ringing?

[Max...]

Thanks guys - really annoyed I could not have more time to try and pinpoint the conditions under which it happened but I could not stay out any longer with a sick feeling 7 yr old for fear of putting him off. When we returned up the channel everything was fine, no other factors to point to engine/cooling problem and when flushing with fresh water I ran it for 10 mins. Oil is nice colour and smell and level is perfect.

We covered trim in PB2 but again not enough time for me to experiment yesterday to get it right.

I'm 99% sure the alarm coincided with high revs - glancing at one point I am sure it nudged over 6000...

Brad - I have a feeling Matt said the same and that an 11 was too low and 14 too high.

Maybe best if I try and get out again with the 14 on and see if it behaves itself.

I have always serviced my own engines (Land Rover enthusiast) but I have no experience of outboards or electronically controlled engines. I really know I should get it maybe up on a dealer's diagnostics but this is a major faff/expense/huge round trip - of course safety comes first so I will take advice on this. I also need to find a marine dealer to trust - years of dealing with un-trustworthy car garages makes me wary!

[matt h]

will post it anyway as might be usefull for someone else!!

its the over rev alarm, as your running the fine pitch prop, IT MUST NOT GO OVER 6000 rpm,!! i have set the throttle so its just on 5950, if sea conditions are perfect or running with the tide, it could go over and the rev limiter will cut in giving a beeping sound, if you swapped the prop the prop to a 12 or 13 pitch it would disappear, in this case (you would have to unscrew the throttle stop as you would need more revs) to run a courser prop,as i have limited the amount of throttle you get as your running a fine pitch prop,

[Max...]

Thanks Matt - and for the PM. Are you sure that's the case, did it happen when you had it? - don't want to get stuck out there!

I'll swap to the 14 and see how it runs. How did you set up the throttle screw though? Is it a case of on a calm sea go to WOT and if it makes, say 5250 RPM, stop engine, cover off, wind out 1/2 turn, try again, repeat if necessary??!!

[Downhilldai]

Originally Posted by matt h

..running with the tide, it could go over

Could it?

[matt h]

its basically the same as running a car in first gear flat out, your gonna over rev it.
as the pitch is so fine, it will over rev, so you increase the length of the throttle stop screw to limit the throttle movement which is easy to find on the o/s rear quarter of the engine.

[Downhilldai]

Or, keep an eye on the tacho and throttle back when it approaches 6k

[matt h]

Originally Posted by Downhilldai

Could it?

well you got me thinking there, if your running against the flow your working it harder, if your running with the tide theoretically less effort reqd, which means if you have WOT ..........

[matt h]

Originally Posted by Downhilldai

Or, keep an eye on the tacho and throttle back when it approaches 6k

of course but in this case the thottle is nailed open and past the 6k marker!! naughty boy!!!

[Max...]

Cheers Matt. What about guaging the adjustment of the stop screw - is it done how I said, ie on the water - run, adjust, check etc? Or does one turn = 250 eg?

[Downhilldai]

Originally Posted by matt h

well you got me thinking there, if your running against the flow your working it harder, if your running with the tide theoretically less effort reqd, which means if you have WOT ..........

Perhaps a strong following wind would cause it, but tide, .......

[matt h]

i would do adjustments on the water as very easy to do. your working rpm should be 5750-6000, if the engine is pulling anywhere in between then all good!!!

[Maximus]

Originally Posted by matt h

i would do adjustments on the water as very easy to do. your working rpm should be 5750-6000, if the engine is pulling anywhere in between then all good!!!

Takeing advice from MATT H about er,.. LOWERING revs!!!??? Like asking George Best how to cut back on the BOOZE!....

[Max...]

Chaps - another thought -changed over the prop last night to the 14 so I can try that but while there I noticed the engine height. According to the Merc' manual and conventional thinking on threads I searched on here it should have the cav plate level or within a inch below the hull bottom:



Mine is an inch above, see pic below (engine fully trimmed in) - would this lead to more likely cavitation on sharp turns and hence more likely to over-rev as noted? I am sure I had it trimmed well in when turning. The mounting holes are 3/4 inch apart so should it be dropped 2 holes?

And any thoughts on a 12 pitch vs 13 pitch on this sort of SR/60hp set-up? As long as it does 30 knts or so I'm more concerned with pull for a mono skiier than top whack.

[Downhilldai]

I run my SR4.7 with the cav plate an inch above the keel line, with no problems.

The lower unit has a 12:22 (1:1.833) ratio, so I reckon a 13" pitch would be right for general running about with 2-3 persons on board (mine has a 12:28 or 2.33:1 ratio and I use a 17" pitch with a Twatsoo 60). A 13" pitch prop should give you 30-35 kts, depending on sea conditions and load. If you intend pulling a skier with 2-3 people on board, you may need to drop to a 12" pitch, but as you already have an 11" pitch, try skiing with that first, before you spend a fortune on props you don't need.

[Max...]

Thanks for that - the 11t was definitely too low I think but I've got my eye on a 13 so will try that. Probably have the 11 and 14 to sell so that should balance out the £'s maybe a 12 and 13 for ski/cruise will be a good pair.