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Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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1998 yamaha exciter 270 twin with rebuilt engines starts

Customer Question

1998 yamaha exciter 270 twin with rebuilt engines starts hard when not used for a week but starts and runs great with daily use. Has hew plugs, filters and electric fuel pumps. Problem is after taking a short break from skiing or tubing one or both engines don't want to throttle up and will stall. After some time of playing with throttles in neutral they will rev and generally run normally although often one will stall and require restarting. I have removed oil injection pumps and capped lines and now use 40/1 mix but problem is unchanged.
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Customer: I have owned boat since new and it has always been kept in a heated and air-conditioned garage and trailered to a nearby lake.
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Submitted: 3 months ago.
Category: Boat
Expert:  RSRBOB replied 3 months ago.

Hi and thank you for your question.

There are a couple of symptoms going on here. For me to narrow it down in my mind, and to provide you with valid information, I need some questions answered.

Chronologically, how do these symptoms correspond to the rebuilt engines?

On the rebuilt engines, are they the original engines rebuilt with OEM Yamaha parts, or are they aftermarket engines?

Also, where chronologically does the change to pre-mix correspond with the symptoms you are now experiencing?

What brand of oil are you using for your pre-mix?

Why did you chose to eliminate the oil injection? I am curious if it failed on you causing the rebuild.

Since I don't know geographically where you are located, is this early in your boating season this year that this happened, or have you been using it for awhile this year already?

Has anyone, especially recently, gone into the carbs to clean or adjust them?

Any non stock modifications to the boat or engines?

If you could fill me in on that info, plus anything else that may have come to your mind relative to any of that, I would appreciate it.


Customer: replied 3 months ago.
Symptoms same pre and post rebuild. Carbs not rebuilt. Oil injection system failure cause of rebuild. original OEM rebuild. This problem occurs at all points of boating season. No non stock modifications. Oil is Pennzoil premium outboard 2-cycle TC-W3 40/1 mix. I also added SeaFoam additive to last mix. This is like a vapor lock condition. Installed electric fuel pumps prior to rebuild.
Expert:  RSRBOB replied 3 months ago.

So you were experiencing this problem before you had an oil system failure? That would mean there was a running problem then a mechanical engine problem? How long has this been going on?

At this point I have reason to believe you have internal problems in the carbs. I suggest taking them apart and carefully inspecting the internals of the carbs. A couple of things I would pay attention to is the needle and seat assembly. Although the 135 HP engines weren't as susceptible to the problem as the 155hp engines, you might be experiencing sticky needle valves. This would prevent fuel from flowing when trying to start it. When you get the needles out of the carbs, use a magnifying glass to inspect the rubber tip. If you see any indications of a ring around the tip, you should replace the needle and seat in all carbs. For reference, I am including a parts diagram. One other thing I noticed, the first year of the 270 was 1999. in 1998 it was a 220. It does make a bit of a difference so is it a 99 270 or a 98 220? If the top of the airbox looks more like an upside down bath tub than it does a bread pan, it is the 135 hp engines. If it looks like an upside down bread pan, it is the 110. I included the diagram for the 135hp carbs.

The needle valve assembly I was talking about is #20 in the diagram.

One last question that seems really random but is more valid than you know, does the oil you are using smell like a vinyl shower curtain when it is in the bottle?


Customer: replied 3 months ago.
It is definitely a 1998 270hp twin. I suppose the oil smells like a vinyl shower curtain. Maybe I should try a different oil before working on carbs. What do you recommend and is 40/1 the proper mix? The engine rebuilder recommended 40/1.
Expert:  RSRBOB replied 3 months ago.

Thank you for the additional information.

I would use the Yamalube 2-W at 50-1. The difference between 40-1 and 50-1 is negligible. It is about 0.9 of an ounce less oil per gallon. I will tell you that oil that you are using caused a lot of problems for us when I was working at Yamaha. It is packaged under a few different brand names, but all the same oil. We had people that were switching to it and all of a sudden having an oil related failure that never had a problem before. We saw it often enough that we were confident it was the oil. One problem is there is no such thing as "oil police" so an oil distiller can put a manufacturer's name on their label without any basis of justification for it. It takes a very long time and a lot of money for a manufacturer to get their name removed from a product like that and quite frankly most do not see the value in the investment of time and money to make it happen. Yamalube 2-W created the category of TCW-3, and is so superior could technically be in a TCW-4 category, but it would be about the only one, so they left it in 3.

OK, I was looking at a dealer's on line parts catalog and they didn't list the 270. I went on Yamaha's site and there it is, so I have that straight now. For the sake of what we are doing, the engines are the same for all 270's.

I still think we are dealing with an internal carb issue here. Are you comfortable taking them off and taking them apart?

Customer: replied 3 months ago.
Taking them off, yes. Rebuilding them, not so much. Probably will switch oil and mix. Ethanol in gas could affect carbs so I will add ethanol treatment and run some more. Engines run great, it is just the stalling upon acceleration after taking a break on the lake that is troublesome.
Customer: replied 3 months ago.
One engine failure was caused by the oil line on the rear of the pump coming off during a ski run. The other was caused by leaves stuck in one head which may have been caused by the detachment of the anode on top of the water vane between cylinder 1 & 2.
Customer: replied 3 months ago.
Which sticky needle are you referring to? # ***** metering needle and #40 pilot are on outside of carb. # ***** float needle is on inside.
Customer: replied 3 months ago.
Which oil is supposed to smell like vinyl curtains. The vamalube or the other stuff?
Expert:  RSRBOB replied 3 months ago.

Not Yamalube. Vinyl curtain smell is bad, very bad. Avoid it at all cost, like, if that is all that is available, don't use the boat.

The needle valve assembly I was talking about is #20 in the diagram.

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