still revs after new prop...

[elake]

Yesterday I made a post regarding my prop may have been spun. It would rev up and not go any faster after going say 5 mph. The engine is a 30hp Johnson on a 1985 Crest II Pontoon, 25'. I replaced the prop and no ahh ahh. Although I think it needed a new prop anyway

engine info:

Model #:J30ELC0A
Serial # E6088307

I thought the engine was the same year as the boat but have no idea. Can anybody tell from the info above so I can get a manual for this engine????

It does get up to full speed now but after a short time it will go back to the 5 mph and then rev again. I can put it back in neutral and then slowly work it back up to full speed about 50% of the time.

The other issue is when it started doing this on Sunday the shaft seemed to be very hot to the touch. Again, last night, after running the engine for about 10 minutes the shaft was extremely hot to the touch. Water comes out of the 2 holes for the exhaust but I do not see a steady stream anywhere. Don't all outboard engines have this steady stream??? Another part to the story is that I can raise and lower the transom manually by clicking it in and out of notches. I have it raised all the way up, it's spring loaded. It was mentioned that the engine could possibly be sucking in air and I should drop it all the way. Although the shaft never got hot the 5 previous times I ran the engine for extended periods of time. I have not tried this yet as I wanted to let it rest last night and get a fresh perspective today. Is it the impellor or water pump??? Is that the same thing? This is my first outboard engine so any help is appreciated. I need a manual so I can better name the parts I'm talking about. Anybody know where I can get one for this engine?????

 

[tashasdaddy]

Re: still revs after new prop...

http://www.kencook.com/evinrudejohnsonmanuals/index.cfm?fuseaction=models.main&year=1985&ID=103224

now it sounds like the prop is caviatating, it's on a toon, and i would say lower the engine. also being hot, it may not be deep enough to get water. the impeller is the rubber fan like, pump inside the water pump that moves the water. if the prop is caviatating, i doubt the pump is getting enough water. if you don't know, when the impeller was last change, it would be a good idea to change it. also running with out water they will overheat and melt. i changed on this week that had melted and clogged the water pick opening into the water pump.

 

[elake]

Re: still revs after new prop...

Thanks for your help over the past couple of days. One question that I am curious about is the stream that is supposed to be shooting out of the engine in the back. Do all outboard engines have this steady stream or more importantly what about a 1985 30hp Johnson?

Thanks for the link, pricey, but probably worth it.

 

[F_R]

Re: still revs after new prop...

Not all, but yours does. Look on bottom of lower cowl, rear starboard (right) corner. You should see a plastic fitting which is the tell-tale. Probably black if they didn't paint over it. Has a hose connected to the inside of it. Check it for being plugged up, both ends and the hose.

 

[Kevin W]

Re: still revs after new prop...

Most newer engines have the teltail water stream and yes yours should.
They do sometimes clog up though.
weedwacker string works wonders on the clogs.

as for manuals Yes they are pricey but look how much your saving by DIY.
70-90/hr
you can get some deals sometimes on e-bay for manuals.

 

[JB]

Re: still revs after new prop...

I think your prop is ventilating, which would account for the cooling troubles also.

That may be what Daddy meant when he says cavitating. They are often confused, but are very different events.

I agree with Daddy's recommendation. Lower the engine so that the anti-ventilation plate (often incorrectly called the cavitation plate) is at, not above, the surface when going full speed.

However, you may actually be cavitating as well,due to a very bad match of your prop pitch to the load. Too much pitch in the prop can cause cavitation, especially when pushing a heavy load like a 'toon. That can only be fixed by going to a correctly pitched prop.

If you have doubts about whether you have a correct prop for your rig, go to the Prop Forum and get the best advice on prop selection.

 

[elake]

Re: still revs after new prop...

Great advice all. I will run some weed whip string through there tonight and see what happens. I ended up getting a manual, selco. It was cheaper than the one posted and seems to be good for what I need. I like the fact that I can view it on the net as well a hard copy. If this isn't good enough I'll get the above mentioned one.

Seems everything is original on the boat so that is what makes me wonder about the pitch. I'm hoping I don't have to replace the impeller until the end of the year but might be best to do it now. Thanks again, what a great site!!!!

Does this sound typical of a impeller gone bad? Of course I will try all of the above suggestions first. If the impeller is shot what else should I be looking for?

 

[fireman57]

Re: still revs after new prop...

These guys are right in the fact that it is definitely time for a water pump. Lot less money than a rebuild. If it is getting that hot there is a reason. Once you get your cooling system working properly you may want to check for spark. When you describe it as getting up to full speed 50% of the time it sounds like you may be losing spark to a cylinder. This same symptom though is one of overheating.

 

[Harker]

Re: still revs after new prop...

Water coming out of the 2 holes sounds like it's a plugged "pee hole" . I would definately change the impeller and possibly the thermostat. Take the "pee" hose off and see if there is a "Mud Dauber" bee nest in it..those things love little holes to pack with leaves and mud. I bet you also have the motor up too high..especially on a 25' pontoon..when everybody goes to the front, it can lift the engine out of the water causing the motor to over rev and setting off the rev limiter in the power pack. The mid sections get pretty hot normally since exaust is going through them .

 

[tashasdaddy]

Re: still revs after new prop...

thank you JB, i ment ventilating, not caviatating. CRS disease.

 

[elake]

Re: still revs after new prop...

Well after reading all of this I decided the first thing I will do is drop the engine down further and then test it out. If it still gets hot after that then I will replace the impeller (which I'm picking up after work). Oh and also clean out the "pee hole".

For those that have done this is it practical to just replace the impeller or should I buy the entire housing kit with gaskets and all, difference of $40.

Again, thanks for the advice. Hopefully one day I'll be able to return the information. PM any IT questions,

 

[perkdp]

Re: still revs after new prop...

May should start a new thread but I'd like to better understand ventilating vs cavitating.

 

[reeldutch]

Re: still revs after new prop...

ventilating is when the prop is sucking air from the surface. therefore the prop will slip and will rev up. less load(air) = more rpm (exesive rpm overev)

so if you mount the motor to high on the transom you have a good posibility to ventilate. specialy in turns.
also if you trim/tilt up to high.

cavitation is totaly different.

on the leading side of the proppellor the water presure is high and the trailing side of the proppellor the pressure is low.
this pressure difference makes your boat move.
sometimes when the presure gets high water starts to boil(making bubbles)at the leading side on the prop and as soon as they get to the low presure side they will explode and can cause damage on your prop.
you also will increase in rpm because again the prop is slipping.

do i make sence? ? ?

 

[elake]

UPDATE: Re: still revs after new prop...

UPDATE: Re: still revs after new prop...

Well, I think we might have her fixed. I took her out last night and man was it ever windy. I think I was drifting faster than my top speed, I dropped the engine, put the hammer down and it seemed to be ok. I have a feeling that there was some ventilating or caviatating going on. I was still nervous to run her at full speed. My buddy brought down a piece of weed whip string. We pulled up to some shallow water, got out and fit the string up there perfectly. First time I pulled it out I noticed some dust on the end of the string. After a few more times some wet mud. Buddy turned the key and wala, my "pee hole" was peeing!!! With that I was not afraid to get on her a little bit but realized it's not a race, so no need to over do it. I don't think I'm going to be breaking any records anytime soon.

Another question if yall don't mind. With the engine now having a nice stream coming out of the tell-tale does that mean the impeller is working properly? The shaft was still warm-hot after the boat ride last night but not burn your fingers hot like before.

Again, I appreciate everyone's help. I managed to get a new prop, manual and hopefully a better running engine, thanks!!

 

[tashasdaddy]

Re: UPDATE: Re: still revs after new prop...

Re: UPDATE: Re: still revs after new prop...

the pee stream means the impeller is working, but does not mean the thermostat is opening. when the tsat opens the water not going thru the pee stream when underway exists thru the exhuast tube thru the prop. one possible way to tell without pulling the boat out of the water, is to put a set of muffs on it, with the engine tilted up enough to see the water come out of the prop. when the tstat opens.

 

[elake]

Re: UPDATE: Re: still revs after new prop...

Re: UPDATE: Re: still revs after new prop...

Thanks, I'll be sure to check that next time I'm out.

the pee stream means the impeller is working, but does not mean the thermostat is opening. when the tsat opens the water not going thru the pee stream when underway exists thru the exhuast tube thru the prop. one possible way to tell without pulling the boat out of the water, is to put a set of muffs on it, with the engine tilted up enough to see the water come out of the prop. when the tstat opens.

 

[perkdp]

Re: still revs after new prop...

Thanks for the clarification on ventilation and cavitation.