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Mercury Marine Force 25 hp Outboard

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NorfolknGood

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Hi chaps

A complete newbie here just bought my 1st outboads 1 is a Force 25HP tother is a Mariner 3.5hp. The Force apparently knocks when running and the previous owner thinks it may be big ends worn. I have not been over to pick the engines up yet which are sitting on the back of a 16' day boat I also bought.

My question is does the prognosis sound correct are the parts readily available in the UK and is it a big job to do? I assume I will be needing a gasket set, bearings.............. are they OEM Force parts or available from any bearing stockist?
 

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The forec 25 is the Mercury motor and depending on year its either a chrome bore or Mercosil block. The chrome bore block if damaged is non repairable except by sleeving which costs more than a replacement block. The Mercosil is a boreable block but needs diamond honing to finish size and only large shops usually carry these type of tools. The bearings on crank and wristpin are needles and will not knock like a babbitt bearing. If a bearing did fail the crank and block will be damaged.
 
faztbullet said:
If a bearing did fail the crank and block will be damaged.
Click to expand...

Thanks for that faztbullet, I picked it up today and have had a quick play. No provision for cooling it so I tried starting it and ran for literally 1 second just to prove it will run. Not long enough to hear this knocking I have been told about but as soon as I get a proper fuel feed (rather than a quick squirt down the carb) and a tub of water to sit it in I can run it up proper and maybe take a vid and post here for your ears and opinion.

It's a 1998 3 cylinder model 2 stroke (you probably already know all that) with the serial No. OE301261

Pulling it over without plugs in all seemed smooth, put plugs back in and wow loads of compression and again sounded fine to my untrained ear. I'm used to small 2 stroke motors from my radio control aircraft anything upto 75cc so know a little about engines.

I will report back soonest with a better test.
 
Oh before I go further................. I assume I will have to make my own bracketry to use a remote steering, gear and throttle system? I can find very little info about the Force outboard on the internet and unfortunately cannot throw £££ at it to fix it and fit it to the boat.
If I have to make my own brackets etc does anyone have any diagrams/pictures for me to work with. TBH I have no idea what the connections should look like.
 
Hi kimcrwbr1

It does have tiller only at the moment but the boat does have throttle, gear and steering ready to hook upto a motor. 25HP is more than enough for here on the Norfolk Broads where there is a low speed limit. I doubt I will ever use it offshore, I dont have enough experience for that but have been on the Broads all my life sailing a 18' traditional half decker single handed at the age of 5.

I have no idea what fuel consumption I can expect from this motor if I is fit for purpose. I guess all depends on how long I want to run it and at what throttle settings.............. will be just over idle for 4mph I guess.
 
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No, but some bolts may break trying to remove things, and the driveshaft might be rusty where the seals ride (correctable).

Jeff
 
Not to be directing you away from this forum,I have had a lot of help with my obsession from the good folk here,but there are a few members of the CMBA,Classic Motor Boat Association, on the "Broads" who may have a good working knowledge of these older outboards and may not be too far from you,and are always willing to help.And Jeff is correct when he says some may break.A good soaking with a good penetrating oil,heat and if you have access to an air gun,low setting and let it work away.In saying that,some will still break
 
Thanks chaps I will take a look at CMBA.

Bolts wont break if I leave em alone:rolleyes: I have had engines before that ran fine and in my 'improving them' by stripping down and renewing anything slightly worn made myself a massive job so now unless something is a real classic or super ***y I leave alone anything that does not need immediate attention.

I just made up a test frame and dunked it in a big bucket leaving the hose running in it and the engine runs fine and throttles well but it does rattle. Apparently the chap I bought it off was sold it as running............... well it runs but does create a racket. It's made the same noise for 2 years and he has not treated it as if it was on it's last legs it's been at full chat being used as a tender to a yacht. Not sure what to do, my local outboard dealers within walking distance wants £42 to run it up and give an estimate on anything that may need work on although I would be surprised if anyone could tell with any certainly just by listening if something is worn and needs a change. Also where do you stop renewing slightly worn but still works ok parts?
 
I'm not worried about the corrosion I can see except that little bit I pictured where the corrosion has blown out the side of the bolt hole through expansion. It's the corrosion I cant see I'm worried about!!!

I have only run the motor for a minute or 2 on my stand and am not sure where the pee hole is, I did not see anything squirting out other than bubbling right near the prop mainly exhaust gasses. Engine did not get to hot to bear my hand on anywhere. The rattle sounds like crank area to me but I did not do the ole screwdriver check just stuck my nose near it. I took a video with my mobile phone but the quality is so poor it give no indication of noise so pointless posting it. I assume from the heat the water pump is ok but that may be 1 thing worth checking regardless I suppose.



*EDIT* Just an the engine again oa couple of minutes and it never went over body temp at idle. The screwdriver said pot No.2 on the head made more noise than 1 and 3. Slightly louder nose with my ear against shaft where there is exhaust gas coming out, 2 holes 1/2 way down the overall height of the outboard, noise appeared to be coming out of these holes.

Oh, don have pot pressure testing facility :(
 
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Forget what I posted about the block as you got that dang old mixed motor. That a chizzler powerhead on a Merc midsection and was only made for 3 years so parts may be a bear to get.
 
The parts are going to be a headache to find,cheap as chips,but most are going to be in the 'States with P&P astronomical money.I have seen them on ebay.co.uk on occasion. That wee mariner is a Yamaha,so I would hold on to that.
 
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