1994 70 evinrude 3800rpm at WOT??

[tengals123]

ok here goes
70 hp 1994 evinrude 3 cyl
vro is disconnected
compression is 125 across all three
new battery
new plugs
carbs have been removed and all cleaned
all carbs have been sync and linked
rebuilt fuel pump
new thermostat

motor starts perfect, runs perfect, but only reaches 3800rpm under load, it doesnt miss at all

pulled the leads off the plugs at wot, and they all dropped indicating good spark to all 3

fuel bulb stays firm

the prop in a 13 3/4 x 15, I tried a 13 1/4 x 17 and lost another 300 rpm with that prop

what could my problem possiblily be?
everything on this motor is perfect only that it gets to 3800 at WOT! the cavitation plate is even with the keel..even at WOT on the trailer (in the water) is still only reaches 3800rpm

I can only now assume it is not fuel related, it cant be prop related, so im thinking ELECTRICAL.

has anyone had this or a similar problem? can anyone help me with this issue? or any advise?

thanks in advance.

 

[tedious]

Re: 1994 70 evinrude 3800rpm at WOT??

What kind of boat is this on? Did it used to rev higher?

Sounds like you need a lower pitch prop, not a higher one.

Tim

 

[tashasdaddy]

Re: 1994 70 evinrude 3800rpm at WOT??

why do you suspect electrical, you have good spark, compression, and IF the carbs are truely clean and working correctly, it is either the wrong prop for the boat, or the boat is waterlogged. exactly what boat is it on?

 

[tengals123]

Re: 1994 70 evinrude 3800rpm at WOT??

im not sure i just bought the boat

but even 3800rpm on the trailer, this makes the hull null and viod

i should still be getting way over 3800rpm on the trailer right?

and also, cant be a massive change in prop to gain an extra 2002rpm can it?

thanks in advance

this is really frustrating me

regards,

 

[iwombat]

Re: 1994 70 evinrude 3800rpm at WOT??

I didn't see mention of a spark check, have you done that?

If spark check pans out, I'd be diving right back into those carbs and putting new kits in.


Edit: Could also be an air leak - some things to check.
1) Use a different (portable) fuel tank and hose.
2) Make sure the jet covers on the carb are tight and have washers installed.
3) Make sure all the fuel hoses are in good shape and have zip ties or hose clamps.

 

[tedious]

Re: 1994 70 evinrude 3800rpm at WOT??

im not sure i just bought the boat

but even 3800rpm on the trailer, this makes the hull null and viod

i should still be getting way over 3800rpm on the trailer right?

and also, cant be a massive change in prop to gain an extra 2002rpm can it?

Can't say I've ever revved up on the trailer, but yes, it seems like it would take the hull out of the picture. However, it seems to me that it's less likely to hit WOT on the trailer than it is out in the water - because its held in place, it's acting like a heavier boat. The only way to tell for sure, on the trailer or in a tank, is with a test wheel.

And yes, it would take a massive change in prop to gain an extra 2000 RPM. From your description, the carbs and spark are doing what they should, so it may be just a radically wrong prop. If you can, borrow a 13-pitch and see what it does for you - on the water, not on the trailer.

Tim