mercury 4cyl 50 hp help /advice please !

[tonyc1]

Hi
Just purchased fletcher boat with 50 hp merc outboard.
Found slow to get on plane but started very easily.
On the way back to launching slip lost 85% of power to engine going full throttel.Had to hop back to slip (took hours and pritty scary with big boats waves ect with no power.
In reverse sounded like i had ful revs but in foward sounded like a dip in the sound of engine at full throttel but slight increase about 3/4. max speed on the way back must have been about 5 knots.
Any help or advise would be appreciated. checked a couple of plugs and they were blackish. Just need some advise as to what to tell an engineer to look for and test.
Kind regards

 

[jfm]

Nice engine, bit of a classic.

I found your description of symptoms bit unclear.

First off, is the vent screw in the fuel tank filler cap open? Cos if it isn't then you will get those symptoms.

If it is revving but not driving the boat, like a clutch slipping, it is likely the rubber bush in the prop needs replacing. Easy, just mail it to steel developments in wimbledon and they'll do a great fix for small £££. Google them

If the engine wont develop power then likely it is fuel or ignition, cos there isn't much else the go wrong on a 2 stroke. You need to check the fuel system thoroughly. Pumps, filters, carb, air vent in the tank filler cap, etc.

If fuel is good then ignition, but that is harder to diagnose. Could be a coil failure at high rpm (look for arcing, look to see if they are well grounded as aluminium corrosion can build up and make a bad earth connection, etc)

What year is it (cos that dictates whether it has points ignition, or electronic but with mechanical distributor, or all-electronic)? If you dont know the year post a photo

Bit hard to say more than that from such a brief set of symptoms....

You could find a good dealer or use www.oldmercs.com for info if you are doing it yourself.

Where are you located? In case someone can suggest a good workshop...

 

[tonyc1]

Hi
Thanks for your reply!
I had a bit of power to get me back but very slow.when i stopped it and put it in reverse it seemed to have loads of power but foward not much but i think it was trying.Iam now going to try quick silver tune spray in a test tank and clean plugs.
ill let you know how i get on.
Thanks again.
I forgot to say for half the day it seemed ok but i was expecting more from it, but when i did get on plane i had to slow it down (kids started screaming!!!)
Any more thoughts well apreciated

 

[aquaholic]

I used to have one of these on a shakespear speed boat, lovely engine but never liked having the vent screw fully open, found I used to have to crack it then half a turn and it would run all day.

 

[landlockedpirate]

I think it sounds like the rubber bush in the prop is slipping(Can you still rev to full throttle when its out of gear ?). You can get the prop redone for about £20. I have used Steel developments before, good quick service. It takes about a week altogether, with the postal time. If you cant wait that long, order a new prop from them and then send your old one off to be repaired. (You will need a spare one, cos it will get trashed at some point )

With regards to the time taken to get on the plane, what model of Fletcher have you got ? A 50hp on the 13ft one will fly, but on the bigger boats it can take a while to get going. /forums/images/graemlins/mad.gif