Low rpm bogging on Evinrude 70 1983

[Stevet1984]

Hi after fixing the head gasket i have got my engine running fairly well apart from it seems to bog when trying to pull away. It seems to struggle to get to 2500 then just seems to come to life and fly! top end is fantastic it eats my bosses 1989 70 VRO! but just got this bogging issue.

I hope to use this boat for wake boarding but as you can imagine it doesn't have the power to lift you out of the water.

Any ideas?

Thanks

 

[Stevet1984]

Re: Low rpm bogging on Evinrude 70 1983

Anyone know?

 

[billy4hp]

Re: Low rpm bogging on Evinrude 70 1983

Anyone know?

Have you checked the basics?

Good even compression across all cylinders?

Good fuel, proper oil mix ratio

Carb's cleaned?

Spark test to make sure all cylinders have a good blue spark?

Sparkplug's good and gapped to spec?

Carb's to Timer Link and Sync performed?


Around 2500 rpm is actually about the most critical point in any marine engine as that is the approx rpm where most hulls plane and require the most torque (therefore putting the most load) from the engine.

HTH

 

[Stevet1984]

Re: Low rpm bogging on Evinrude 70 1983

Hi Thank for your response

I'm trying to track down a compression tool to check the compression.

Fuel is good and mixed to 50:1

We have had the carbs apart and all looks good and clean

All cylinders have a good spark and new plugs.

Haven't done a link and sync.

Just got the book on this outboard today and am finding a little hard to understand.

Cheers
Steve

 

[Stevet1984]

Re: Low rpm bogging on Evinrude 70 1983

Have you checked the basics?

Good even compression across all cylinders?

Good fuel, proper oil mix ratio

Carb's cleaned?

Spark test to make sure all cylinders have a good blue spark?

Sparkplug's good and gapped to spec?

Carb's to Timer Link and Sync performed?


Around 2500 rpm is actually about the most critical point in any marine engine as that is the approx rpm where most hulls plane and require the most torque (therefore putting the most load) from the engine.

HTH

Compression is 140 on all 3 cylinders

new fuel mixed at 50:1

We have stripped one of them down and it was spotless not yet done the other two.

All sparks are good

All plugs are new and set correctly

I have synced the carbs.

The prop was a 14x17 which i believe was too big as there was only 3mm between the prop blades and the caverty plate. So i have replaced with 13-1/4x17 which i beleive to be the std propeller.

When doing the head gasket i also found that they thermostat was missing so that has now been replaced. The water now coming out of the pee hole is now warm and the top exhaust is now fairly hot! Is this right?

i have recorder a video on my phone of the acceleration.

You can kinda hear me saying the RPM as i go.

www.visitaldeburgh.co.uk/MOV00002.3gp

from starting till 3000 at WOT there is almost no power. then suddenly it just goes as you will see.

Any help on this would be fantastic!

Thanks Steve

 

[tashasdaddy]

Re: Low rpm bogging on Evinrude 70 1983

stripping carbs down is not cleaning them, did you remove the jets with the special tools? did you use rebuild kits? if not you wasted your time. have you heard of ethanol? check you timing, then do a linc n sinc. this is a step by step procedure to coordinated timing and carbs, it is only covered in your OEM Evinrude service manual.

good info here. http://forums.iboats.com/showthread.php?t=299680

 

[Stevet1984]

Re: Low rpm bogging on Evinrude 70 1983

stripping carbs down is not cleaning them, did you remove the jets with the special tools? did you use rebuild kits? if not you wasted your time. have you heard of ethanol? check you timing, then do a linc n sinc. this is a step by step procedure to coordinated timing and carbs, it is only covered in your OEM Evinrude service manual.

good info here. http://forums.iboats.com/showthread.php?t=299680

The one that we stripped down we cleaned out even though it looked clean. I would use a rebuild kit but im having trouble finding one in the UK.

I have heard of ethanol but we dont have it in our fuel over here so thats not really a problem.

What are the chances of the time being out? i dont think that it has ever been altered?

I did the link and synk on the carbs.

Im going to take them allapart this week and see what i find.

Steve