1989 yamaha 150hp v6 problem...

deftonead

Cadet
Joined
Jun 17, 2009
Messages
8
hi everyone,
i am new here and have no real experience with fixing boat engines. recently i have received a hand me down boat from my grandfather. it is a 19' sea squirt with a 1989 yamaha 150hp 2 stroke v6 outboard. the engine runs good in idle and at slow speeds but when you open her up she starts erratically revving up and down... or gaining and then losing power. this problem seems similar to the rpm loss posted by wwwes in the forums. in his case it was a clogged vst filter causing the problem. i have purchased a manual for the engine to help me out and nowhere in there can i find what a vst filter is. could someone please explain what that is and where i could find it.
there is also an overheating alarm that sounds shortly after i start the boat whether or not it is in the water or has the earmuffs on. im thinking that there might be a problem with the water pump even though there seems to be a good steady stream of water coming out the back.
also, the boat has not been to well maintained being that my grandfather is old and it sat around for quite some time not being used. keep in mind that many of the parts are factory and have probably never been changed or lubricated for that matter. there are a number of things that could be causing this. any help would be greatly appreciated.

thank you
 

deftonead

Cadet
Joined
Jun 17, 2009
Messages
8
Re: 1989 yamaha 150hp v6 problem...

ok... ill get straight to the point so you guys do not have to read that paragraph.

what is a VST filter?
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 1989 yamaha 150hp v6 problem...

your 1989 has no VST.
post a fullmodel number so we know exactly what we are disscussing.
your in for a lot of maint catch up.
fresh or salt water usage history?
 

deftonead

Cadet
Joined
Jun 17, 2009
Messages
8
Re: 1989 yamaha 150hp v6 problem...

i checked the model number and it is a 150 ETXG. i did some looking around and someone told me that they did not make that model in 89 and that it was really an 88 but it says right on the motor that it is an 89.... so i am going to stick with it being manufactured in 89.

as far as usage history, it has been used primarily in salt water in the tampa bay area. i have taken it out probably about 10 times last year and once this year.
 

deftonead

Cadet
Joined
Jun 17, 2009
Messages
8
Re: 1989 yamaha 150hp v6 problem...

ok, so the engine is overheating and i have been getting flat spots when i accelerate. the manual i have says that it could be one of the following:

bad spark plugs
incorrect ignition timing
defective water pump
the thermostat is no good
the main jet in the carburetor needs cleaned
or there are deposits on the pistons or combustion chamber.

now i have already purchased new spark plugs, i was planning on getting a new thermostat, i will be disassembling the lower gear casing and checking the water pump next week and i am going to clean the carburetor.

i have a few questions to ask.

would ignition timing be the same as the timing and sychronization of the entire motor or is it a different timing just for the ignition system?

thank you
 
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