60's or 70's 33hp bigtwin problem

[dondre47]

Hi im new to this forum and been looking around. sounds like alot of you are experienced on repairs/problems on these motors amd maybe can help me. Just bought my first boat and took it out today to test it out on the lake. When i throttle up the top speed is very slow and the motor dosnt seem to be running at full potential. Every once and a while i would get a power kick and it seems like everything is running good but it wouldn't last (3 seconds or so)and it would go back to running at low power.

After an hour of testing i turned it off and restarted about a half hour later. when running this time the motor would stall like it was out of fuel. I realized that i had to pump the gas pump at the tank to force fuel in the carb to get back to shore. i lost power to my battery also probably from trying to start it so much. Tomorrow i will check the fuel pump but i also still have the low power issue. I would appreciate some help if possible.

Thanks

 

[F_R]

Re: 60's or 70's 33hp bigtwin problem

Hi im new to this forum and been looking around. sounds like alot of you are experienced on repairs/problems on these motors amd maybe can help me. Just bought my first boat and took it out today to test it out on the lake. When i throttle up the top speed is very slow and the motor dosnt seem to be running at full potential. Every once and a while i would get a power kick and it seems like everything is running good but it wouldn't last (3 seconds or so)and it would go back to running at low power.

After an hour of testing i turned it off and restarted about a half hour later. when running this time the motor would stall like it was out of fuel. I realized that i had to pump the gas pump at the tank to force fuel in the carb to get back to shore. i lost power to my battery also probably from trying to start it so much. Tomorrow i will check the fuel pump but i also still have the low power issue. I would appreciate some help if possible.

Thanks

Your story is almost a classic one. Your motor is running on one cylinder. Once in awhile the other one will kick in and give you that surge of power. And now the "good" one isn't firing either.

It is NOT a fuel problem, although that is not to say that you might not have a fuel problem in addition to the first one. The carburetor feeds both cylinders, so it cannot cause a running on just one problem.

What it IS, is an ignition problem. It could be as simple as bad spark plugs, but in all probability it has bad (cracked) coils. Those old OMC motors are notorious for that. They cause the exact symptoms that you and a few thousand other people describe. New ones are available right here at iboats.

 

[dondre47]

Re: 60's or 70's 33hp bigtwin problem

Thanks for the response. I'll check the coils. Is there anyway i can check the year on the motor? i can see the model number but no year

 

[tx1961whaler]

Re: 60's or 70's 33hp bigtwin problem

post the model number. We can look up the year based on that.

 

[dondre47]

Re: 60's or 70's 33hp bigtwin problem

The only numbers i can see on it are

serial number:442119
model:B7E

 

[tx1961whaler]

Re: 60's or 70's 33hp bigtwin problem

Rx-13 33 Hp 1965
Rxe-13

Rx-14 33 Hp 1966
Rxe-14


Rx-15 33 Hp 1967
Rxe-15

Rx-16 33 Hp 1968
Rxe-16

 

[dondre47]

Re: 60's or 70's 33hp bigtwin problem

Actually i took another look at the evintude manufacturs plate:
model number-40552A
serial number-c442063

Do any of you know a trick to take the flywheel nut off without an impact gun as it turns while i try to loosen it. I read somewhere here that the nut is right hand thread am i right? thanks

 

[tx1961whaler]

Re: 60's or 70's 33hp bigtwin problem

Nut is normal thread: righty tighty, lefty loosie
You can use a strap wrench to hold onto the flywheel to keep it from turning.
I wrap a nylon strap around mine and tie it off on a sturdy part of the case.

A 40552 is a 1965 40 HP

 

[jdsgrog]

Re: 60's or 70's 33hp bigtwin problem

The model number shows that it is a 1965 40hp motor. Is there reason you said it's a 33hp?

I have a Johnson 33hp, and you want to make sure you go through all the diagnostics. A good place to start is checking for spark. No spark, then an ignition problem. Could be as simple as cleaning points, most likely, you may need to replace coils, points, and condensers. There may be a slight chance you may have a bad cutoff switch.

As for getting the flywheel off, if you have a strap wrench that will fit around the flywheel, that is best. I just jam a screwdriver between the teeth of the flywheel and the starter bracket to secure the driver. Need to be careful the screwdriver is secure before you try to take off the nut.

 

[dondre47]

Re: 60's or 70's 33hp bigtwin problem

thanks i ended up using an impact gun. now to take out the flywheel im letting it sit with some wd40 cause i already broke a bolt using the puller. should i use heat or keep trying with this puller.

I checked the spark plugs and on the top cylinder im getting no spark changed the spark plugs around and same top cylinder nothing. since im going to get under the flywheel i might as well change both coils.

 

[tx1961whaler]

Re: 60's or 70's 33hp bigtwin problem

Try to get some grade 8 bolts for the puller. They should be 1/4 -20 bolts

 

[jdsgrog]

Re: 60's or 70's 33hp bigtwin problem

Yes, use the puller with grade 8 bolts. When you get it tight, give the puller a good whack on the center with a hammer. The flywheel should pop right off. When you put the flywheel back on, do not use the impact wrench. You need to torque the flywheel properly to avoid any potential damage to the flywheel and have the motor run properly.

 

[F_R]

Re: 60's or 70's 33hp bigtwin problem

Yes, use the puller with grade 8 bolts. When you get it tight, give the puller a good whack on the center with a hammer. The flywheel should pop right off. When you put the flywheel back on, do not use the impact wrench. You need to torque the flywheel properly to avoid any potential damage to the flywheel and have the motor run properly.

The single most important thing you will be doing during this operation: Correct installation of the flywheel. The crankshaft and flywheel tapers must be shiny clean and dry. Then you MUST use a torque wrench and tighten the nut to 100-105 ft/lbs. Ignore these instructions and destroy a perfectly good motor.

BTW, you can soak that thing till doomsday with that WD-40 and it won't help a bit. You must use the proper puller and bolts to get the flywheel off. That would be Grade-8 bolts screwed in 7/16", no more and no less. It WILL come off, but takes a tremendous amount of pull.

 

[dondre47]

Re: 60's or 70's 33hp bigtwin problem

Hi thanks for the help. I got the flywheel off with some of your help. Im taking out the (cracked) coils now and i cant seem to figure out how to get the spark plug wires out. I've taken out the 3 screws but plug wires are going straight into the coil from underneath. am i missing something?

 

[F_R]

Re: 60's or 70's 33hp bigtwin problem

Hi thanks for the help. I got the flywheel off with some of your help. Im taking out the (cracked) coils now and i cant seem to figure out how to get the spark plug wires out. I've taken out the 3 screws but plug wires are going straight into the coil from underneath. am i missing something?

Just pull. The wires just poke into the hole in the coil. May be slightly stuck from deteriation of the plastic.