Yamaha 30HP 2 Stroke Running Problems

The Mornin Wood

Recruit
Joined
Nov 19, 2006
Messages
3
Hi Folks,

I'm new here and a relatively new boat owner and don't know anything other than what I've learned from having the engine serviced and reading the manual. I've got a duck boat (The Morning Wood) that has an 89 Yamaha 30 HP 2 stroke prop with console controls. It's a pull start and was purchased used. Since we purchased it over a year ago, we had it overhauled and they put a new carb in it (the other was fine), cleaned out the pumps, replaced the impeller, etc.

After we had it tuned, it ruled. It started with a few pulls, idled perfectly and was great. Then I bought a new boat.

It should be noted that i removed it from the old boat, and transported it on its side to the shop where they mounted it on the new boat, replaced the throttle cables but kept the same control box. They replaced the plugs, which was nice. I noticed that the throttle cables seem very long (the console is in the rear of the Jon boat and the cables are so long, they coil once and then go into the engine.

Well now it starts after several pulls (granted it's much colder now) and then runs a bit strange.

First off, it often runs loud at first, with what seems like limited power. This might be because it's cold but I'm not sure.

Next, it now dies sometimes when I idle it after running it. It starts right back up with one pull, but this is annoying.

Finally, on Saturday, we were running up river and the alarm went off and the RPMs went way down. I immediately killed it and checked the oil resevoir--plenty full. I then restarted it and it ran just fine, though a bit loud. Later, when were done hunting, it took forever to start but then ran fine until we had the idling issues again. No alarm, though.

What am I dealing with here? Did something happen when I transported the engine on it's side? Would this have to do with the new throttle cables? Or is it something unrelated?

A few other notes: I always run premium unleaded. We have been running the carbs dry after use since someone told me to do so, but it seems like this has made the starting harder. When I first start it, I pump the bulb about three times. Am I flooding it?

I know nothing! Help! Thanks in advance!
 

The Mornin Wood

Recruit
Joined
Nov 19, 2006
Messages
3
Re: Yamaha 30HP 2 Stroke Running Problems

I should also add that it's spitting plenty of water--this doesn't seem to be the problem. It was overhauled last spring, run about 5 hours this summer, and then transferred a few weeks ago.
 

andy6374

Lieutenant Commander
Joined
Aug 4, 2005
Messages
1,617
Re: Yamaha 30HP 2 Stroke Running Problems

Engines run rough until they warm. Let it warm for at least 5 minutes this time of the year, I'd go 10 minutes. If your tstat is stuck open then it will never get warm and will run rough. Have you inspected it?

Did they just clean 1 carb? How come not both.
 

The Mornin Wood

Recruit
Joined
Nov 19, 2006
Messages
3
Re: Yamaha 30HP 2 Stroke Running Problems

Thanks, Andy. We'll try warming it up for a longer period of time. Any reason why this would cause the alarm to go off?

I should have been more clear--they cleaned one carb out and replaced the other.

How do I inspect the thermostat?

Anyone else have any ideas?
 

andy6374

Lieutenant Commander
Joined
Aug 4, 2005
Messages
1,617
Re: Yamaha 30HP 2 Stroke Running Problems

If you don't know the last time your waterpump or tstat was replaced, just replace them. They should be replaced every 2 seasons or so.

Not sure why the alarm went off. How are all the oil lines? Good condition? Tight fittings>
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Yamaha 30HP 2 Stroke Running Problems

Alarms go off because of overtemperature or an oil related problem. A thermostat stuck shut will cause overheating. A thermostat stuck open causes poor running as the engine never gets to operating temperature. An oil related problem can kill the engine. Also running the carbs dry is not really running them dry. They do not completely empty which leaves plenty of space for air. Gum and varnish build-up may be part of the problem here. Treat every tank of fuel with SeaFoam to prevent this problem. If your engine "requires" premium fuel use it. If not, don't. Sounds like you need to have a reputable shop service this engine.
 
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