Horizon 26 / 1GM10 Power issues...!

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Mwinda

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New (ish) boat to me so still on the learning curve....
1986 Hunter Horizon 26, with an Outboard -> Inboard convert about 10 years ago, but only 100 engine hours.
Under power the performance seems dismal. With the engine seeming "happy" we seem to make 1-2 knots. Higher revs does make the boat go faster, but lots of black smoke, oily stuff coming out in the exhaust etc.
I don't have a rev counter, so no idea what the actual revs we are cruising at is.
Engine oil remains a nice light colour after the last change in the Spring, no obvious leaking of oil from the engine.

So...
What sort of performance should I expect for a boat of this size, under auxiliary?
(she sails fine!)
If there is a problem, where should I be looking?
Thanks for any advice in advance!
Jonathan
 
I've got a 27'er with a bit more displacement that will do about 5knots in flat water at about 2,800 rpm. Summat not right with yours.
Other forumites are more clued up than me but to kick off:
serious fouling on hull and prop but then you say she sails fine,
exhaust elbow clogged up but seems unlikely after 100 hours
The black smoke is unburnt diesel, I believe but why and where is beyond poor me.
 
I have a Hunter 245 with a 1 GM 10 in.
Normally I would see about 5 knots ish max with about 4.5 cruising.
If as you say she sails OK , I would suspect the prop is fouled or the boat is over propped or possibly has the wrong gear box ratio.
It is also possible the exhaust elbow is blocked due to carbon build up from not getting up to temperature. This is caused by just using the engine to get in or out of the Marina and never giving it about three quarters max revs for any length of time.
It would be worth removing the elbow and checking this out.
 
Thanks all, that's helpful.
What about the injector? Would a dodgy injector result in that sort of performance?
She starts easily though, and idles nicely.
Jonathan
 
jakeroyd said:
I have a Hunter 245 with a 1 GM 10 in..
Click to expand...
Another 245/1GM owner here, agree with Jakeroyd's comments.
If the problem has appeared suddenly, may simply be some rubbish picked up on the prop.

Problem described is typical of a very badly fouled prop, but would be odd to find a fouled prop on a boat with a clean hull.

Gearbox ratios vary but around 2.6 : 1 is common (the ratio is stamped on the side of the gearbox) and the most likely prop is then a 2 blade about 14" dia and 10" pitch. If the prop is a lot bigger than this, either in terms of diameter or pitch, or a 3 blade, could explain a lot (wouldn't do a lot for sailing performance either).

Think you will need to dry the boat out and have a look (once you have checked the exhaust elbow and gearbox ratio).

Oh, and check the prop turns easily with engine not running (!) and gearbox in neutral.

For a newish engine which starts and idles OK, the injector is not the first thing I would suspect. I assume the engine will rev reasonably high with no smoke if gearbox in neutral ( if the answer is "smoke even when box in neutral" then I have run out of ideas!).
 
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Is there enough air getting to the engine air intake? Too little air can cause black smoke and the higher the revs, the more air is needed.
Perhaps whoever converted the boat did not allow large enough vents to the engine bay.
On our previous boat (Hunter Horizon 23) the (inboard mounted) outboard would only run well if the engine locker was left open -for the same reason.
 
Thanks
Its a two blade prop - and not especially big - pic attached.
When I dried her out in May the prop and shaft did have lots of hard worm shell things on, but I scraped them off.
 
I had the HH 272 and would see about 5.5 knots with a two blade folding. A weeded hull would easily knock two knots off but yours does not sound healthy.
Take the exhaust elbow off and check it is all good, its an easy job.
If that does not work and your fuel filters are good then look at the injector.

All jobs on the 1GM are easy as its a simple engine that is normally very reliable.
 
Thanks all appreciated, will run through that check list when I get down next.
Fuel filter should be ok, I changed that recently, and the diesel looks clear.
Gearbox oil level again was fine earlier this year (until then I had no idea it had a separate gearbox dipstick..... a worry I know....)
Jonathan
 
looking at the picture , I can not see detail of course but just going on that it looks the same as my prop.
It would have to be very badly fouled to reduce your speed to 2knots.

I suspect you are not getting anything like full revs from the engine.
 
jakeroyd said:
looking at the picture , I can not see detail of course but just going on that it looks the same as my prop.
It would have to be very badly fouled to reduce your speed to 2knots.

I suspect you are not getting anything like full revs from the engine.
Click to expand...

see what rpm you get out of gear
check the shaft is free turning, with engine off
 
Just following up the ,
"are you getting full revs" issue it might be worth getting hold of a laser device to check the rpm you can get either in neutral or under load.

From memory a 1GM10 should rev to about 3600 rpm under no load conditions.
A laser rpm meter would confirm this.
You sometimes have to attach something bright like a bit of singer foil to the front vee pulley. Then use the tool to make the measurement

Something like this

http://www.ebay.co.uk/itm/Handheld-...quipment_ET&hash=item19d010da36#ht_5843wt_922
 
OK, another easy check on the 1GM10 is the air filter. It can get choked. Insufficient air is usually the cause of black smoke. Mine suddenly developed a taste for lub oil. The breather, located on the top of the rocker cover, had a reed valve. This "encourages" the crankcase to experience low pressure. Mine was not flat, so didn't seal well. It's a £3 part (but don't forget to order the gasket, too - another £1.50) so it's a cheap job even if it's in vain. I'm assuming you're not losing a lot of crankcase oil (it doesn't take a lot to show up in the exhaust). There is a oil scraper ring on the piston which, if it's broken makes this worse but it's a big (=expensive) job to do even an investigation on that. Broken compression rings will mean the engine is unlikely to start, Trying to swng it over by hand will let you know how good the compression is.
 
Laser rev meter - now that looks like a cool toy!
Having nearly killed myself unsuccessfully trying to hand-crank the engine I think we can safely assume the compression rings are ok ;-)
Thanks again - what a helpful bunch you lot are!
 
By the way, a 1GM10 is more than adequate for a 26 footer and the Hunter is an easily driven craft anyway. I know people with 18 & 23hp engines fitted to Contessa 26's but they're both overkill. If you fancy a twin or FW cooling by all means get a Beta 12 but nothing bigger.
 
I fitted a 1GM10 to my old Hunter 26 and it was quite happy to do 6kn in a calm with just a 2 blade prop. Yours has a fault somewhere
 
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