Reviving Old Yamaha Engine

 Gday fishos ill start off with this is a great forum and awesome community so looking forward to contributing more. Basically we have a 1990 yamaha 40 HP 4-stroke from my grandfather and me and dad are in the process of trying to get it up and running again so ive got a few questions so bear with me.

So the engine hasnt been run in around 10 years (only have an idea) most of which has been in our garage. Aside from a bit of surface rust on the exterior it seems to be in pretty good condition but this is just looking on the outside. Dad has already removed the carbs and taken them apart to check their condition and they were looking pretty sweet execpet for a few seals which we have already replaced. Thermostat was buggered, spark plugs need replacing and we've just removed the lower leg so we can replace the water pump and we have the parts for all that on the way. If ive missed any other details let me know. Ill put some pictures in on the exterior of the engine. 

So here's where we need some help (see pictures below the question if it helps)

We have basically no experience in terms of prepping an engine after this amount of time of not being used or boat engines to begin with so what other things should we be looking at to make sure its good to go or even if it will start at all? Done some research for replacing fuel lines but any other info would be a big help

As i said thermostat was buggered and there's still lots of crap from where it was, whats the best way to clean this out?

One of the other issues with the motor is the tilt as seized from rust. Any ideas on how we can fix this or are we better off replacing whatever parts need replacing? 

Also near the water pump under the damper seal (just going off diagrams online) the metal looks like its been pretty corroded will this be an issues later on even after the seal is replaced?

Last question is when we removed the lower leg there was quite a lot of oil around the water pump. We arent sure if this is normal or because we had the engine on its side for a while or if there might be a leak somewhere. Any idea which it could be and if its a leak where it might be from? In the above picture the water block was completely full of oil which we wiped out.

Asking a lot but basically any info on the questions ive asked or other things that i havent mentioned would be really appreciated

Cheers and tight lines. 

Image Upload: 

Posts: 204

Date Joined: 02/01/12

 Looks like a 2 stroke to me

Sun, 2018-01-07 09:06

 Looks like a 2 stroke to me

squidvicious1's picture

Posts: 610

Date Joined: 22/07/10

 Start with its a 3 cylinder

Sun, 2018-01-07 09:13

 Start with its a 3 cylinder 2stroke,as by the oil tank and flat head with no valves overhead.youre doing well so far by pulling the motor apart and understanding the basics.Products like saltaway will remove the corrosion to a degree.

Get a owners manuel and take the motor to a Yamaha mechanic and discuss what parts are needed and what you can do about the tilt yourself. Might pay to ring first as they may be busy after the break.

Hope that helps.good luck.that model is a very good one with having 3 cylinders balances itself better than a 2 cyl.

Posts: 9

Date Joined: 13/12/17

 Yeah you're right its a 2

Sun, 2018-01-07 09:26

 Yeah you're right its a 2 stroke. Thanks for the advice

Posts: 151

Date Joined: 18/10/12

 give boat city a call,

Sun, 2018-01-07 09:38

 give boat city a call, experts on yammys

Darren253's picture

Posts: 352

Date Joined: 23/07/16

This Guy

Sun, 2018-01-07 10:41

His range of videos should answer pretty much all of your questions above! Tons of information especially for older style outboards

Faulkner Family's picture

Posts: 14270

Date Joined: 11/03/08

 your doing the right thing

Sun, 2018-01-07 10:45

 your doing the right thing by doing the research as you go. little by little you will get there. never done an outboard but have done car engines before. patience is a virtue when it comes to these kind of things. as Squidvicious said get a bit of advice from thse in the know. a bit of knowledge can go a long way


RUSS and SANDY. A family that fishes together stays together

scano's picture

Posts: 1069

Date Joined: 31/05/07

You do know

Sun, 2018-01-07 11:35

 That the tilt of the engine is via the small lever below the front of the engine cowling? Near where the remote steering arm connects. 

I say this because it is unlikely that a manual tilt motor would have its tilt ceased from simply sitting in the shed. 


It it is a small basic spring loaded lever that locks the motor in position. Where abouts are you located? Happy to come and take a look mid week after work if that helps? (Perth metro)

i got a small 2 stroke yammie myself. Not all that difficult one you learn what’s what.




Posts: 9

Date Joined: 13/12/17

Both levers and all the

Sun, 2018-01-07 12:33

Both levers and all the speings work for the tilt but axel it sits on (not sure what its called) is rusted and looks to be why its siezed we think. Thanks for the offer, might take you up on it but we are taking it in this week to see idlf we can get some snapper bolts removed. 

Posts: 204

Date Joined: 02/01/12

 Before you get too far into

Sun, 2018-01-07 11:38

 Before you get too far into it, do you have the forward control set for it? Doesn't look to be a tiller steer version. Maybe wasting money if you have to add on the cost of forward control set or convert it to tiller steer, it will all add up

Posts: 9

Date Joined: 13/12/17

 Yeah its just disconnected

Sun, 2018-01-07 12:15

 Yeah its just disconnected right now to make thinhs easier

Posts: 225

Date Joined: 08/10/13

 Have a sniff of the oil in

Sun, 2018-01-07 14:12

 Have a sniff of the oil in the water pump. If its gear oil or 2 stroke oil. If its gear oil you will need to replace the gearbox oil seals.  When you first run it use premix 50/1 fuel the oil injection may not work.

Posts: 9

Date Joined: 13/12/17

 How can you tell the

Sun, 2018-01-07 14:50

 How can you tell the difference?

Posts: 225

Date Joined: 08/10/13

 You should change the gear

Sun, 2018-01-07 19:36

 You should change the gear oil anyway. Drop it out and see if it is the same oil. You will need a good big screwdriver to loosen the filler and drain screws. You may need to tap the screwdriver with a hammer they can bind on the seal.  Gear oil stinks.  2 stroke oil stinks as well but has a distinct ammonia or similar smell and is sometimes blue in colour. 

Brock O's picture

Posts: 1589

Date Joined: 11/01/08

 Just a thought would be to

Sun, 2018-01-07 15:49

 Just a thought would be to pull the heads off, youll need to order new head and cover gaskets and have a manual and torque wrench to put back on..two stroke heads easy...good to look at deflectors and clean water ways as good to clean and inspect. 

This was an issue with early model Johnsons, water galleys and especially deflectors.



Posts: 9

Date Joined: 13/12/17

 Cheers Brock O will

Sun, 2018-01-07 15:55

 Cheers Brock O will definatly look into it

Brock O's picture

Posts: 1589

Date Joined: 11/01/08

 Remember the CRC or

Sun, 2018-01-07 16:53


Remember the CRC or inox...nice and easy on the bolts..