Yamaha 70hp issues!

[Rhosneigr Gaz]

Morning all

Not sure if this is in the right section but here goes....

I have a 1985 70hp Yam which i've just spent a few quid restoring, it's had.....

1. New charging circuit
2. New prop
3. Refurbed lower leg
4. new steering
5. Heat exchanger cleaned

So in preperation for this years first outing i fired her up, ran 100% on the muffs at home, no problem.

Got her to the beach and fired up no probs again, HOWEVER when i put her in gear she wont take any revs. She goes into gear fine and will spin the prop fine at tickover, however as soon as you open the throttle she just bogs down and dies.

I have in my head that it's a fuel starvation issue, does this sound possible?

Any help would be much appreciated!

Included a pic so we know what motor i'm on about! (Pre resto and looking tatty!)

 

[LittleShip]

Hi Gaz


Yep sounds like fuel starvation.

Have a look at the carburetor needle it may have some crud on it which is stopping full flow. (assuming that it has Carb)

Tom

PS you didnt come back to meet the guys at Pilots

 

[Rhosneigr Gaz]

Hi Gaz


Yep sounds like fuel starvation.

Have a look at the carburetor needle it may have some crud on it which is stopping full flow. (assuming that it has Carb)

Tom

PS you didnt come back to meet the guys at Pilots

Ha ha, no i didn't because my 25 litre tank on that boat was giving me cause for concern! I appologise!!!!

You'd be amazed how much fuel Rhosneigr to Llandwyn at full chat uses! (Because who drives sensibly in a SPEED boat!)

I could have come back but with only a 5 litre spare i didn't want to chance it.

I probably COULD have done it, but am a safe boater when the sprog is in tow!

Back to my problem......

It has 3 carbs is line, one for each Cylinder....

Might be time to get it serviced i suppose, am gonna check the fuel pump first, hope for the cheap option!!!!

 

[Rhosneigr Gaz]

P.S. keep an eye out for this boat for the rest of the summer as the Yellow/white one has gone!

 

[tinkicker0]

Ha ha, no i didn't because my 25 litre tank on that boat was giving me cause for concern! I appologise!!!!

You'd be amazed how much fuel Rhosneigr to Llandwyn at full chat uses! (Because who drives sensibly in a SPEED boat!)

I could have come back but with only a 5 litre spare i didn't want to chance it.

I probably COULD have done it, but am a safe boater when the sprog is in tow!

Back to my problem......

It has 3 carbs is line, one for each Cylinder....

Might be time to get it serviced i suppose, am gonna check the fuel pump first, hope for the cheap option!!!!

Fuel filter? Following that low fuel delivery from the pump.

The book will probably have a spec for minimum fuel quantity delivered in one minute. Probably ITRO 1.5 litres / min. although I know nuthing about outboards, just a Yam / Honda motorcycle techie.

 

[Philiz]

You're right, most probably fuel trouble. I'd do what Tom suggest and clean the carbs out first. I'm not familiar with the engine but there must be a filter somewhere which may need changing or cleaning out. If you're not confident to tackle it yourself, Kwackers is yer man, he's well versed on these engines.

 

[rr_123]

I had a similar problem with my "new to me" Princess and her old volvo petrol engine a couple of weeks ago. A mate and his new girlfriend came over for the shakedown; but the engine was "hunting" and not delivering constant power, also failing to respond to a handful of throttle so we canned it.

Said mate and I agreed that this was clearly fuel starvation, and proposed cleaning of fuel filter, checking of fuel pump, and rebuilding of carbs as the best courses of action, starting with the simplest first.

However; the next day I had another idea and took the boat out again, but this time I opened the fuel cock and it worked just fine! (doughnut of the week award for me...)

Don't overlook the simple stuff like blocked breathers on the fuel tank etc.

 

[Kawasaki]

Gaz, rr123 may be right, it sounds like something simple
That unit was one of Yams best.

If it's idling ok on the water but won't rev when put in gear it could very well be a fuel related prob
But you say 'a new charging circuit was fitted' do you mean the stator plate, coils under the flywheel?
'Heat exchanger'? that's confused me on one of those?
Anyway
Only a few miles from you.
Your welcome to run it over for a quick check
Or I can pop over for similar.
Nice picture on the beach by the way!

 

[Rhosneigr Gaz]

Thanks for that, any offer of help will be taken up!!!!

Yes it had a new stator(?) so the flywheel has been off, maybe upset the timing advance thing?

The heat exchange is the radiator core thing that the water cool through, it had silted up overthe years!

Where are you based then (I'm sure i asked u before but i got a head like a sieve!)

U around next weekend? I'll pay!!!!

 

[Kawasaki]

Thanks for that, any offer of help will be taken up!!!!

Yes it had a new stator(?) so the flywheel has been off, maybe upset the timing advance thing?

The heat exchange is the radiator core thing that the water cool through, it had silted up overthe years!

Where are you based then (I'm sure i asked u before but i got a head like a sieve!)

U around next weekend? I'll pay!!!!

Ah, see what you mean ref 'radiator core' thing!
'Advance thing' may be playing up but unusual.

£100 an hour OK?

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