Outboards

[adzzy]

Hi Raiders

I am looking to buy a second hand outboard and have had debates with a few mates regarding compression testing the argument is that all plugs do or do not need to be removed for this test does anyone have educated knowledge on this matter

motor is 100hp yammy 2 stroke

cheers Adzzy

[jewieslayer]

hi i am a mechanic every plug needs to be removed so u can check all cylinders

Cheers Jewieslayer

[FISHLETIC]

Yep i'll second that , each cylinder must be compression tested individually

[dangles]

definately remove all plugs before u do the compression test, its amazing at the difference in readings when only the plug on the cylinder you are checking has been removed.

just saw your other post. i used to do comp tests cold,then warm the engine up and do another test

Edited November 26, 2008 by dangles

[adzzy]

Hi raiders

Thanks for the help just hope the readings of test are good now

[a boat]

Hi raiders

Thanks for the help just hope the readings of test are good now

Hi, yes you want to do a compression check with all the plugs out and if possible both cold and hot to see if ther are big differences. With any brand if engine the actual number is not critical, they just want to be even or within 10 % of each other.

What I would do if I was you, considering the age and the fact it probably still has the original head gaskets, is to say to the seller you want to remove the heads and inspect not only the bores, but the block for corrosion. Replacing head gaskets is preventative maintance and should be done about every 10 years and that Yamaha also has anodes internally that need to replaced to help with corrosion from inside out.

If the bores look good and you can still see the hone cross marks and no signs of corosion, then buy it and re-install two new head gasket, service the water pump, replace the filters and plugs and you will be good to go.

Cheers,

Huey.

[adzzy]

Hi, yes you want to do a compression check with all the plugs out and if possible both cold and hot to see if ther are big differences. With any brand if engine the actual number is not critical, they just want to be even or within 10 % of each other.

What I would do if I was you, considering the age and the fact it probably still has the original head gaskets, is to say to the seller you want to remove the heads and inspect not only the bores, but the block for corrosion. Replacing head gaskets is preventative maintance and should be done about every 10 years and that Yamaha also has anodes internally that need to replaced to help with corrosion from inside out.

If the bores look good and you can still see the hone cross marks and no signs of corosion, then buy it and re-install two new head gasket, service the water pump, replace the filters and plugs and you will be good to go.

Cheers,

Huey.

cheers Huey

the motor belongs to a family friend they bought it new in 89 and it has done only 6 hrs per year but for the last 4 years it has only been kicked over for 10 min every 4 months but had a yearly service

is there anything else i should look for?

and what would it cost to do these works you mentioned

Thanks

Adzzy

[a boat]

Hi Adzzy, if it all goes according to plan and no bolts break or are seized then to service the head gaskets, service the water pump and powerhead will cost about $800. Best to remove the heads B4 you buy it to make sure there is no corrosion, which considering what it is and the age there might be.

Cheers,

Huey.