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Old 04 May 2014, 17:15   #1
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Country: UK - Scotland
Town: Aberdeenshire
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Make: Ribcraft 4.8m
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Tohatsu one step away from being an anchor!

Got up at 5.00am to launch out of Cruden Bay. Picked up my brother on route and we were on the water by 7.30am. The sea was calm which is a first for the east coast!

I have an issue with the main engine. I had a oil recirculation pipe blow off in April (first trip out in April). Thinking it was carb related I'd striped them the previous week. The engine is a 2006 Tohatsu 60hp, 2-stroke. The carbs were clean as a whistle, no deposits, etc. Fuel was fresh. It's an autolube engine (Quicksilver topped up).

I also renewed the primer bulb after that first outing with a Quicksilver replacement, as the original rubber bulb was hard.

Not far out of the harbour after launching - the engine felt bogged down. Normally the Tohatsu is eager and quick to respond, but it was very sluggish. I'd reset the fuel pilot screws on the carbs to 1 5/8 turns from lightly seated, but it was struggling. After various impromptu stops it ended up at a full 4 1/2 turns out, which is crazy.

The engine pumps water fine. The impeller was changed last season. I also renewed the fuel pump diaphragm, thermostat, last year, etc. All genuine Tohatsu parts, etc. The head gasket spark plug holes had threaded at the start of the season, so I had them retapped (steel inserts) and used a new gasket. No indication that the gasket has failed.

The spark plugs are from last year. I changed them to another set I had on board and it did seem to make a difference. I'll try changing the sparks, but wondered if anyone has any other suggestions. Can the timing go off, or could this be a weak spark from one of the HT leads?

With two-up we topped out at 27mph which is poor. It normally does well over 30mph and the power delivery is instant and smooth.

Earlier thread here for info: Tohatsu running rough
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Old 04 May 2014, 18:21   #2
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I have the same engine and ended up having the fuel pump replaced after repeated loss of power. The pump is apparently similar to other outboards and the engineer put a used Yamaha pump on. Not looked back!
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Old 04 May 2014, 19:22   #3
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Country: UK - Scotland
Town: Aberdeenshire
Boat name: Sula
Make: Ribcraft 4.8m
Length: 4m +
Engine: Tohatsu 60hp + aux
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Quote:
Originally Posted by pow2gran View Post
I have the same engine and ended up having the fuel pump replaced after repeated loss of power. The pump is apparently similar to other outboards and the engineer put a used Yamaha pump on. Not looked back!
Interesting, thank you for the response. I rebuilt the fuel pump last year with genuine Tohatsu diaphragm parts last year. I'll strip it down and check it again.

How did the issue manifest itself with you? Did it happen all of a sudden, or prolonged issues?

How many turns out from lightly seated are your carb pilot screws - 2 full turns?
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Old 05 May 2014, 05:03   #4
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the fuel pump on my tohatsu 50 is rubbish as well, I've got a replacement Mikuni one to go on, comes standard on seadoo/yamaha jetskis
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Old 05 May 2014, 15:42   #5
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Country: UK - Scotland
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Cheers Roflhat.

I'm going to check compression on all the cylinders before throwing yet more money at this problem.
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Old 05 May 2014, 15:49   #6
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Cheers Roflhat.

I'm going to check compression on all the cylinders before throwing yet more money at this problem.
friend of mine had similar symptoms with a 100hp yam 4 stroke. It turned out to be the HT leads & coils- he replaced both at same time so not sure which resolved the problem.
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Old 05 May 2014, 17:06   #7
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Country: UK - Scotland
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Cheers Henry.

I'm inclined to think its electric rather than fuel. Last year I renewed the inline fuel water separator, cleaned the fuel filter on the side of the engine, rebuilt the fuel pump (genuine Tohatsu parts/diaphragms), and just replaced the fuel primer bulb to Quicksilver part. All the fuel hoses are in excellent condition and I've checked the connectors, etc. The carbs have been rebuilt countless times, and are spotless. Fuel was new and oil is from Autolube reservoir. Butterfly choke valve was seized last year with a little corrosion, but it moves freely.

Electric wise, I've just order new NGK spark plugs. The battery was on trickle charge the day before we went out. I tested it tonight and it's reading 12.4v. The HT lead and coil pack (3F3-06040-0) are a 70 part plus shipping. They do come up on Ebay from time to time, but given its difficult to test that could be false economy? Is there any way to test them. I have a multimeter but I assume they require something a little more sophisticated?

Not sure if it's related, but the tachometer is on the blink too. I know the green wire is the pulse signal. Could be something or nothing?
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Old 05 May 2014, 17:11   #8
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Originally Posted by spartacus View Post
I'm inclined to think its electric rather than fuel Henry. Last year I renewed the inline fuel water separator, cleaned the fuel filter on the side of the engine, rebuilt the fuel pump (genuine Tohatsu parts/diaphragms), and just replaced the fuel primer bulb to Quicksilver part. All the fuel hoses are in excellent condition and I've checked the connectors, etc. The carbs have been rebuilt countless times, and are spotless. Fuel was new and oil is from Autolube reservoir. Butterfly choke valve was seized last year with a little corrosion, but it moves freely.

Electric wise, I've just order new NGK spark plugs. The battery was on trickle charge the day before we went out. I tested it tonight and it's reading 12.4v. The HT lead and coil pack (3F3-06040-0) are a 70 part plus shipping. They do come up on Ebay from time to time, but given its difficult to test that could be false economy?

Not sure if it's related, but the tachometer is on the blink too. I know the green wire is the pulse signal. Could be something or nothing?
one way you can test if it is the ht leads is to spray some WD-40 (what we did to diagnose my mates dad's problem) if you see some improvement then it would indicate it could be the HT leads.

I mean at the end of the day is 70 and the engine may benefit from new ones anyway because everything needs replacing eventually.
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Old 05 May 2014, 17:16   #9
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Tohatsu one step away from being an anchor!

I might be barking up the wrong tree here BUT, doesn't the tacho signal come from the charge coil on the stator?

Have you checked output voltage whilst engine is running?
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Old 05 May 2014, 17:18   #10
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I might be barking up the wrong tree here BUT, doesn't the tacho signal come from the charge coil on the stator?
think we may have found the problem

get that ht kit ordered

(assuming A1an is right then everything makes sense )
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