Yamaha 90 stalling - 89 vs 87 Octane

I went to my local Marine Part and started out with just getting the fuel pump rebuild kit - basically a bunch of gaskets. I took the pump in and showed it to the sales guy and he looked at both sides of the pump. There are two metallic pieces that should be "floating" - you an see it below. It's the part on the right in the photo. The other one is on the other side.
One didn't have any bounce back so I replaced the entire pump ($53).

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Upon further inspection he noted that I had the original pump on (he could tell be the plastic diaphram. Which upon further inspection it was torn. So between the two it could have been having issues.

Here you can see the tear - hopefully.

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I also went ahead and replaced the thermostat - I read somewhere that there's a safety shutdown if the engines running too hot. I seriously doubt that was an issue - especially on start up, but it's a cheap easy one to knock out.

I fired her up the next day no issues - need to get her on the water under load AND buy a Seatow membership.

While there I priced out a carb rebuild - about $600 including parts. I watched a couple videos on how to do it, but I'll draw the line on that effort and leave it to the pros. My gut tells me it's a rebuild. Perhaps just a sticky float.
 
At the age of your engine having the carburetors gone over would seem like a good idea. Maybe just having them properly adjusted and synched can make a world of difference in regard to overall engine smoothness. With a flow instrument they set and synch the idle screws using the flow meter, then open they the throttle some and adjust the linkage so they are all showing equal flow.
D.D.
 
Yeah...for $600 it's not a bad deal. Annualized that's like $50-$75.

Problem is waiting the 4 weeks. Just about every good eating fish is in season right now - and tarpon season is in full swing.

Going to get a Seatow membership, call a couple buds before I head out and see how she does. Most of the fish I do is inshore/inside Tampa Bay. She's sunning strong, but that's in the driveway - need some load on her.
 
There is enough wrong with the pump to cause your problem.

It down' hurt, to squirt carb clearer in and let it sit for a few hours, then drain--blow with an air hose. This is assuming that the carb drain is easy to get to.

But the boat is idling well, and the high speed has been intermittent...prob not carb. On the other hand, the above simple technique (wile not sub for full rebuild) often will take care of minor issues.
 
I have had two 2-stroke Yamaha 90's like yours on my 22' cruiser. The original was purchased in 1990 and ran for 20 years and over 3000 hours. I bought a new 2010 model and it is almost identical to my original 1990 model. Nice to have the old one for spare parts. They never changed the design so I am assuming yours is the same as mine.

You have 3 carburetors on your engine and the jet openings are very tiny. Those little black specs are enough to clog a jet. Trust me I know, as one of mine plugged 40 miles off shore in the Pacific. The fuel line that feeds the carbs consists of two Tee's to feed the bottom two carbs and a 90 degree elbow to the top carb. Every problem with plugged carbs was always the top cylinder. I think it was way the fuel flowed to the carbs that always carried the junk to the top cylinder. Eventually, I had to replace the engine as the top cylinder got scored from running leaner than the other two.

My advice is to stick to one grade of gas, get the carbs tuned on that grade, and keep on eye on the top cylinder. I did and got 20 years of life out of my engine. It also never hurts to throw some 2 stroke oil in the fuel tank if you are making a long run just in case your oil injection system is not sending enough oil to each of the cylinders. The amount of oil varies depending on the RPM level and any blockage in the oil injection lines could also be exacerbated at low RPM levels.

It also doesn't hurt to have a good 8hp kicker on your boat that uses the same fuels as your main engine but on a separate tank. I have one, and that is how I made it back in from 40 miles out in just under 7 hours.
 
More sound advice; especially on the existing Yamaha...hope to get her out prior to this weekend in a local river prior to this weekend.

Interesting you mention the oil - I saw a pronounced kink in the line; not enough to block oil (I'm burning it on every trip), but it was an observation of "Hmmm...that looks a bit off."

For reference here's the schematic for lines to the carbs. It's basically the same page as the fuel pump. Need to look in "under the hood" to see how easy it is to access the lines.

Here's the schematic to the carbs. Looks like #25 is the drain plug.

Venturing towards the land of the professional mechanic.

Supposedly these 2-stroke Yami 90's are true workhorses and just go and go...

Reality is she sits mostly idle during Sep-Apr - I'll fire her up every other week or so, but come summer she's out there running and working hard for me. I seldom cruise below the 3000 rpm range. 4000 is a sweet spot.
 
jbdba01":1n01gpgf said:
More sound advice; especially on the existing Yamaha...hope to get her out prior to this weekend in a local river prior to this weekend.

Interesting you mention the oil - I saw a pronounced kink in the line; not enough to block oil (I'm burning it on every trip), but it was an observation of "Hmmm...that looks a bit off."

For reference here's the schematic for lines to the carbs. It's basically the same page as the fuel pump. Need to look in "under the hood" to see how easy it is to access the lines.

Here's the schematic to the carbs. Looks like #25 is the drain plug.

Venturing towards the land of the professional mechanic.

Supposedly these 2-stroke Yami 90's are true workhorses and just go and go...

Reality is she sits mostly idle during Sep-Apr - I'll fire her up every other week or so, but come summer she's out there running and working hard for me. I seldom cruise below the 3000 rpm range. 4000 is a sweet spot.
Click to expand...

#25 yup, float bowl drain :wink:
 
Well...ran her reasonably hard yesterday anywhere between 3000 and 5000 rpms. Couple short stops and one long one (two beers worth at the local watering hole). She ran like a champ; no stalls no hesitation...I'm still thinking about those carbs and getting them redone, but I'm not terribly keen on taking them apart [yet].

I had forgotten how nice it is to run in smooth conditions - so long runs at high rpms was very doable.

Regardless I'll be taking her out this weekend.

Let's she how she does - filled her up with more ethanol free 89.

Thanks for all the advice folks. Excellent feedback. :thup

Until then some beer porn from our local watering hole "The Beer Shed".

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Will do - is there a recommended one? I have the Sta-bil version, but I'm not so sure it's a ring cleaner - more of a fuel stabilizer. Right now I don't use it much because I'm running fuel through her pretty darn fast - 10 gal a trip/once a week.

On the down side - on Sat looks like we'll be at 15 knots from the west for winds so I'll probably take a knee on going out Sat. Need a bigger boat.

On the plus side - on Sat I'm heading to look at a 25' C Dory.

Going to scrutinize where livewells go. Much less can you throw a cast net off her. Can't figure that out from pics/schematics.
 
Ran her reasonably hard yesterday. Good 2-3 hour work out on the river, out to the bay, and back - mostly around the 4000 rpm area; couple times ran her at 5000 rpms. Slowed down in a couple few ilde/no wake zones. No issues...

Shut her down a couple times and fired her back up. No problems.

Ran her some more at home on the flush. No problems.

Good advice guys - probably would have missed the fuel pump as the issue.

$55 later and I believe I'm in good shape. Will have the carbs looked at later - drawing the line on DYI there.

Tarpon season ain't over yet, but Grouper season is upon us. Let the games begin [again].
 
Glad the problem is resolved. I would not touch the carbs at this time. But putting a dose of carburetor cleaner in the tank of fuel may be prudent. Using the motor (and fuel) is the best thing to do!.
 
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