early 70 evinrude 33hp will not rev.

[corcan1]

got a early 70's 33hp evinrude electric start short shaft given to me and im having problems.

motor starts well, idles a little slow but nothing major.
motor will not rev.. seems to only reach 1/4 to 1/2 throttle..
everything looks to be moving freely, carb is opening all the way, just doesn't seem to make much of a difference past half throttle.

good compression, good spark. no fuel leaks...

this motor may have been sitting for a year or more, i have no clue.
i have it on a 14foot fiberglass.

did some searches here in the forms and from what i've read this could be a carb problem. probably a dirty/clogged jet. just wanted to get a second opinion first.

 

[F_R]

Re: early 70 evinrude 33hp will not rev.

Do not go messing with the carburetor...at least till you rule out whether it might not be running on one cylinder. Carbs do not cause running on one cylinder when a single carb feeds both cylinders (like on a 33)

 

[tashasdaddy]

Re: early 70 evinrude 33hp will not rev.

i agree with F_R, check spark first. what are your compression #'s? good tells me nothing.

 

[Basszilla4]

Re: early 70 evinrude 33hp will not rev.

Not that this is your problem but it was the exact same thing mine did. I bought my boat from a guy in Missouri. Bought off of eBay. Went and got boat from him and he started engine just to show it ran. Brought it home, then boat sat for two years without running. Finally got it legalized, put fresh gas in it, and took it out for first time about two months ago.

Same thing happened. Would start instantly, idled great, but when you gave more than a few inches of throttle, engine would bog bad and I could tell something was wrong. First thing I did, check compression. Over 120psi on all three cylinders. Great spark. So had to be fuel. Upon inspecting, there had been a brand new fuel pump installed before I bought. So, hmmmm, what could it be?

Knowing a lot about motorcycles, mostly 2 stroke dirtbikes, I thought I'd clean the carbs. After taking off the carbs, I noticed a blue waxy looking substance in bottom of float bowls. Didn't even realize there was a high speed jet down in float bowls, was so caked with gunk. So, took carbs apart, carefully keeping an eye on how they came apart and where all the jets were set at.

Took boat out after cleaning and WHAM!!! Boat ran like brand new. I was amazed. On dirtbikes, there is a pilot jet that is only used during idle to quarter throttle. Once you start to open throttle further, you start using the main jet. If main jet is clogged, bike would idle fine, but **** poor when on the throttle.

Now, I am not saying that this is whats wrong with your engine, but something to consider. Sitting with fuel in the float bowl for long periods, not good. Hope this helps and doesn't confuse the heck out of you.

I agree with these other posts though. You need to check compression, spark, and fuel delivery. If all these check out, then I'd clean the carb(s). Keep us posted...

 

[corcan1]

Re: early 70 evinrude 33hp will not rev.

took a look at the engine this morning, took compression - 115 each cyl. next checked for spark, top cyl was dead. now i dont get this.. i checked them when i first put the motor on my boat, they looked great, nice blue spark. anyways, gonna pickup 2 new ones on Monday.


also decided to open the carb and do a cleaning / blowing of the passages / jets. everything looked nice and clean. no varnish. i did notice it was mising the cork gasket at the bottom of the highspeed jet! thinking this would cause some problems aswell... i have a 28hp johnson which is almost the same except its a long shaft. took the carb off the 28 and used that gasket for the 33.

also switched the props from the 28 to the 33 as the one on the 33 was in poor shape.

will let you's know how well i made out next week.

 

[corcan1]

Re: early 70 evinrude 33hp will not rev.

2 new plugs in, both have nice blue spark. motor seems to run the same, but i only have it in a barrel of water so cant rev it....

the motor makes a few pfft noises now and then, im guessin cause the engine is still cold. it seemed to clear up after a bit....

a neighbour of mine told me you could remove the prop and rev them up a bit in a barrel of water and this would not hurt them. is it true?

 

[corcan1]

Re: early 70 evinrude 33hp will not rev.

took boat out over the weekend, motor now rev's nice!! very pleased with it. but it seems like when you open the throttle past 1/4 it slips. the motor rev's up but you go no where... let off on the gas and it starts to push again.

is there some kind of clutch in the foot?

i do have a spare foot of my 28hp that i could try.

thanks for the tip on checking the spark and if anyone has any suggestion on this slipping problem.