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Old 08 June 2013, 11:10   #1
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tohatsu 25 problem

Hi...bought a tohatsu sb and tohatsu 25 2 stroke today..put it straight into the water as soon as I got home...its got much less power than ny tohatsu 18 and doesn't like tickin over it seems to feel bogged down.

Iv changed the plugs
Taken the carb off and cleaned all the jets which looked ok....still running rubbish...

The fella iv bought it off has said he'll be cool about the situation so all good there...
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Old 08 June 2013, 12:30   #2
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Quote:
Originally Posted by woz72 View Post
Hi...bought a tohatsu sb and tohatsu 25 2 stroke today..put it straight into the water as soon as I got home...its got much less power than ny tohatsu 18 and doesn't like tickin over it seems to feel bogged down.

Iv changed the plugs
Taken the carb off and cleaned all the jets which looked ok....still running rubbish...

The fella iv bought it off has said he'll be cool about the situation so all good there...
If hes cool, take it back and get ur money back, could be a can of worms when u start lookin.... He might be fine with helpin out with a 100 quid bill but if it turns into a 500 quid bill bet he wont be so cool then!!!
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Old 08 June 2013, 16:47   #3
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Twatsoo 25s are generally bullet proof. Check fuel, check sparks, check carbs?
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Old 08 June 2013, 17:04   #4
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Hi...its running fresh fuel with decent oil..fitted a pair of new plugs..took the carb off and removed both jets and they are clean...the carb was spotless..that's about the limit of what I can do without some fresh advice...
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Old 08 June 2013, 19:30   #5
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My first plan would be to check the compression. If there is a loss in power it could relate to there being low compression caused by ruptured piston rings or ruptured head gasket.

When you say it doesn't like ticking over to you mean it runs at too high RPMs during tick over or it is just very lumpy and can't keep running in tick over. When my little 4hp was running badly (high RPMs) during tick over I replaced the carb gasket and it was fine. It also increased top end power.

Is the air filter clean? If it is all clogged up then it won't be able to breathe very well resulting in loss in power.

It might also be worth checking the RPMs it is running at then referring to the owners manual to see what they should be running at.

These are the checks I would do. Pretty simple and cheap. A carb gasket is going to cost you no more than a fiver and you can probably borrow a compression tester from someone you know if you don't have one already.

If you don't know how to do a compression test, all you do is take one of the spark plugs out and screw the end into into where the spark plug was. You then crank the pull starter until the pressure on dial stops rising, then repeat on the second cylinder. Simple

Also, you say you cleaned the jets, did you clean the bowl as well?

Henry
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Old 08 June 2013, 19:46   #6
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Hi henry...the engine feels heavy as its reving in gear.it doesn't have any zing to it.almost as if the chokes on...when its ticking over out of gear it gives a slight cough n stops.but this is reliably intermittent...after a run I checked the colour of the plugs and they were the right colour...ill take it to a tohatsu dealer and let them take a look...it almost sounds electrical???
Cheers woz
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Old 08 June 2013, 19:50   #7
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Originally Posted by woz72 View Post
Hi henry...the engine feels heavy as its reving in gear.it doesn't have any zing to it.almost as if the chokes on...when its ticking over out of gear it gives a slight cough n stops.but this is reliably intermittent...after a run I checked the colour of the plugs and they were the right colour...ill take it to a tohatsu dealer and let them take a look...it almost sounds electrical???
Cheers woz
I would be inclined to say it is a restriction of air flow. If it sounds like it is on choke then the fuel mix is too rich in the mixture of air and fuel.

Carb gasket gone me thinks, so there is no suction so the carb can't draw very much air. It is very easy just to wip off the carb and check the gasket, but before check the tubes that carry the air to make sure they haven't perished.

henry
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Old 08 June 2013, 20:39   #8
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Woz,

Have you tried the 25 with the fuel hose & tank of the 18, check. Other issues to check, when starting engine with choke (pull/push) check that butterfly doesn't stay at closed position. Choke knob could be fully in and butterfly jammed at close position inside carb.

Due to lack of lube, salt, etc in shaft, could be sticking and small spring will not have the sufficient force to open butterfly. Remove carb air silencer pull/push choque, check proper working condition. If ok, you could have a spun prop...perform a prop test.

Happy Boating
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Old 08 June 2013, 21:07   #9
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Hi...I haven't bothered with the tank supplied with the 25 because it was bone dry so I used the tank and fuel pipe off my 18 I already had 20 ltrs mixed up. I checked movement of the choke butterfly in situ and when I stripped the carb..all well greased and free moving..

What do you mean spun prop??
It doesnt sound happy (sweet) either in or out of gear almost running on 1 .1/2 cylinders..when ticking over it gives a little cough n cuts out..when reving in gear its flat...out of gear it free revs ok ish but doesn't zing . Sounds boggy
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Old 09 June 2013, 03:46   #10
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I think you've had a fair go at it so I'd suggest you take it back to the seller for a refund if you have this option before you go any deeper. Get him to take it to the Tohatsu agent and then buy it once done. If you do it the other way around you'll end up footing the bill, which may be harder to recover from the seller if he already has his sale.... Carrot & Stick

If you do too much more, he may try to renege on any agreement on the basis of "tampering" . As it stands you seem well covered so don't put yourself on a sticky wicket.

www.BoatsandOutboards4Sale.co.uk
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