1997 yamaha 2 stoke 90 hp

this motor is clean and well taken care of. It does get used alot(fresh water only). i was wondering if you guys might be able to help.

the other night i was on my way back to the boat ramp and she went out on me. lots of what i think was steam not smoke was bellowing from the the cowling.there was a detonation of some sort and the power loss was gradual.it went from half power to almost nothing then it made the detonation noise.

being pretty good at working on cars i took my compression tester home and checked all 3 cylinders. 90 psi on all of them across the board. the motor will turn over and it doesnt sound like there are any parts clanking around inside of the clyniders. i am going to drop the lower unit and check that tonight.i drained the lower unit last night and there were some small metal slivers on the drain plug ...just a couple nothing of major proportions.

so it the compession is good that rules out anything on the head gasket side of the motor right?

copression is good-
and there is still feul going into the motor--so fuel is good.
plenty of voltage from the batt.--no prob there

i havnt had time to change all the plugs yet but i will tonight.

if you guys can think of anything that would be of use to me it would be great thanks, eric

[jb123]

overheat, impeller go out??

did the motor shut down completely?

fuel pump ?

motor shut down after a sec. ,still getting fuel but will not run,

[jb123]

do you have spark ?

unplug 10 pin main harness see if this makes a difference. you can start motor by touching brown at start relay to hot on relay.

[jonp]

I have 90 as well... 90 PSI is low.... Mine is about 125 PSI across the board stone cold...Since it is all even you may have blown head gasket.

As JB pointed out did it go into reduction mode when it cut out? An over heat situation can destroy a head gasket as well.

ok pulled plugs and wipped them off,checked for spark and it is good,motor will crank and idle now.but will not do anything more then that. i did notice that there is no water comming out so i am pretty sure the water pump is history.i am going to change that asap. i figure if i change that then at least i can see where the gasket blew if it external ,right? being that there was lots of hot steam comming from under the cowling then water had to be comming from somewhere.

no i didnt go into reduction mode,i went into *****ing motor mode.lol

OK motor will crank up but not run smooth - 92 is all i can get on the presure gauge when testing the cylinders.i need to order the gasket sets and the water pump assymbly.

6H1 C90TLRW
04/97
cu7386

all numbers on the motor


and 68803- stamped on intake??
68802 stamped on head?

anyone have a gasket set part number and water pump # ?

i can really use some help here.

90 PSI is low but it is strange that this low reading is consistant amoung all 3 cylinders. Regardless, For the price of a head gasket, I'd be pulling the head to see what is going on in there.
You can look up part numbers at Yamaha's Web site:
http://www.yamaha-motor.com/outboard...home/home.aspx

got it - will be putting on tonight.