Engine won't run in water but fine on muffs

m22nly · 13 April 2017, 06:43

Hi I recently sold my rib with a 96 mercury 70 oil injection on it . I didn't use the boat at all last year but was fine the year before that . I got the boat out and ran it up and it was all fine but the new owner has now contacted me saying the boat doesn't run once it's in the water but is fine on muffs. One message said he took it out and it stalled on him at 3000 revs then it wouldn't start again . I can't see how it could run on muffs but not in the sea . Any ideas?
Thanks guys

jeffstevens763@g · 13 April 2017, 07:21

Did it stall because the intake was blocked at sea?

m22nly · 13 April 2017, 07:23

If you mean water intake I would say no . It had a new impellor when last used and is pumping water really well.

m22nly · 13 April 2017, 07:25

I wasn't there though. It's the new owner having the issues but I kind of feel responsible. I wondered if the carbs could need cleaning due to no use last year ?

jeffstevens763@g · 13 April 2017, 07:30

Quote:

Originally Posted by m22nly

If you mean water intake I would say no . It had a new impellor when last used and is pumping water really well.

No I mean seaweed or plastic bag they drop to safe mode around 1000 rpm then cut out I think mine is 3 mins not sure on your old engine how long it runs if it runs on muffs it's not carbs IMO

warder54 · 13 April 2017, 07:39

Is he using bad or dirty fuel?, try a fresh fill tank.

beamishken · 13 April 2017, 07:41

Muck in the carbs is a good possibility and could give those symptoms. When it's on muffs with no load it only needs a small amount of fuel to run , once in the water with a bit of load it needs more fuel as it has work to do
Without hearing or seeing it its only guessing but cleaning the carbs is a good starting point as it is a common problem after a long layup and if you or the purchaser can do it yourselves then it's free too

John Kennett · 13 April 2017, 12:27

My first guess would be the primer bulb. The internals are prone to breaking down with age which blocks the flow when above tickover.

m22nly · 13 April 2017, 12:46

I have forwarded these suggestions to the new owner but I am about 4 hours drive away so not really ideal for me to pop down and take a look but feel bad it's playing up for them when they have just bought it . I'm sure it can't be much . Thanks for all the advice guys hopefully it will be s simple fix

Xk59D · 13 April 2017, 13:10

Fuel filter or bad fuel is very possible, had the same thing last year.

willfinch36 · 13 April 2017, 13:54

Friend had a similar issue just last week. One of the coils was faulty.

jncunliffe · 15 April 2017, 07:06

I had a very similar problem just a few weeks ago. Fine on muffs, but wouldn't maintain tick over when the leg was fully submerged. Fix was just to tweak the idle adjuster screw a fraction and up the revs.

It does sound to be fuel related so before cleaning the carbs I'd suggest making sure they're getting some fuel in the first place. Check for fresh fuel, replace/drain the inline filter/water separator, check the bulb by squirting some fuel into a bucket (look for anything floating), look in the engines fuel filter (is it clean, does fuel, flow through the mesh). Checking this should take about 10mins. Worth doing before a carb strip down.

HTH,
Gadge