74 Mercury 650 Rebuild or no??

[bnold]

Ok bear with me for a little story and some history...

Basically I was clearing some land for my father in law... Cut down a few trees and look there is a boat! (His response, oh that?s where I left it)... Long story short I acquired the boat with the motor mentioned in the title. Estimated sit time was approx 10 years

I was young and in a hurry and put a new timing belt on it hooked up some fuel, sprayed some carb cleaner set a rude time and she ran... never well, fouled plugs, idle was horrible, studder on accel etc.. Bad running and no surprise still used it as a run around for a year or 2.

Fast forward another 2 years of sitting I decided to pull it out and make it run right. Before doing anything I pulled the plugs and did a compression check with a good gauge.
#1 I pulled 135# (I thought the throttle was staying WOT but later realized it closed, so the #1 measurement was taken with throttle closed.. oops, all other measurements were taken at WOT)
#2 145#
#3 145#

Sprayed some light lubricant into each and retested
#1 150#
#2 160#
#3 160#

Ok, so I started pulling covers etc... Front, sides, intake exhaust as I knew this motor has eaten a few water pumps so I wanted to make sure paths were clean and peace of mind for me...

So far this is what I know what I want to do:
Replace water impeller
Replace Thermostat and poppet thingy...
New cover gaskets
Carb rebuild
Fuel pump rebuild
New hoses throughout
New wires where required
New plugs

Ok so here is the question... Do I pull the head to check pistons and cylinders? Or with the compression readings I took am I ok?
Decision is the difference from spending a good bit of money... New seals, new gaskets, new rings etc...

What is the general recommendation? Money is always tight, but want to still make the smart choice...



Question #2... The flywheel has been unbolted before (8 bolts removed, not pulled) and I doubt it was placed on in the same orientation... How can I ensure it is on correctly? There are no timing stickers or marks that I know of on the flywheel. I plan on placing a timing sticker and needle once I'm ready to set TDC etc... I have heard that the flywheel has to be oriented correctly, but I didn't know if it had something to do with the stator or something, or if it was just due to lining up timing marks in which case it doesn't matter to me as I have none.


Question #3 at some point in history when a water pump was replaced I'm sure the little piece that activates the reverse lock (arms that lower onto the pin to keep the motor from jumping)... What is that piece called!! And where can I buy!! Plastic piece I believe...

I'm sure I will have more questions as I dig into this and I appreciate any response. This forum has helped me in the past, a lot of knowledgeable people on here...

Thanks
Brian


Serial Nubmer is a 381..... I'll report the full number when I look again..

 

[fishdog4449]

Re: 74 Mercury 650 Rebuild or no??

You should be ok with those compression readings. The top is a bit lower, but definitly within proper specs. Not positive, but I'm pretty sure it piston/cylinder walls were scored or bad rings you would be seeing a much bigger difference. (75psi vs the other two @ 160) A decarb (see engine FAQ) might bring that top cylinder up a few pounds if the rings are stuck.

 

[Laddies]

Re: 74 Mercury 650 Rebuild or no??

1. That engine don't have a cyl. head to remove, just a waterjacket cover but the compression is fine and when you change the popit and thermostat you will have the exhaust uncoverws an you can see the pistons at that time.
2. To index the flywheel tyurn #1 piston to TDC, get the timing indicator out of the starter rope bag install it in the port side bracket and with the bolts out turn the flywheel till it lines up to the indicator and install the bolts.
3. Rev .lock cam heres a link or any Mercury dealer. http://www.mercruiserparts.com/Show...desc=GEAR+HOUSING+ASSEMBLY,+COMPLETE+(PAGE+1)

 

[bnold]

Re: 74 Mercury 650 Rebuild or no??

Thanks for the response.

1. Yes sorry mistyped I suppose... New the cylinders would have to come off... Already have the covers off.. rings look free and pistons dont show to have any immediate damage... hard to tell... Do the pistons have a sharp edge or are they more rounded? these are more rounded? just want to make sure that is not wear...

2. I dont have the timing indicator... not in the rope bag, never seen it... Are there timing marks on the flywheel itself? raised bosses? or detents or something? There is no sticker or other indication... That being said can I place the flywheel in any orientation that I please create a new timing indicator and then place a timing sticker to correlate with TDC on the flywheel?
3. Yes!! that is what it is!! Thanks!

1. That engine don't have a cyl. head to remove, just a waterjacket cover but the compression is fine and when you change the popit and thermostat you will have the exhaust uncoverws an you can see the pistons at that time.
2. To index the flywheel tyurn #1 piston to TDC, get the timing indicator out of the starter rope bag install it in the port side bracket and with the bolts out turn the flywheel till it lines up to the indicator and install the bolts.
3. Rev .lock cam heres a link or any Mercury dealer. http://www.mercruiserparts.com/Show...desc=GEAR+HOUSING+ASSEMBLY,+COMPLETE+(PAGE+1)

 

[bnold]

Re: 74 Mercury 650 Rebuild or no??

You should be ok with those compression readings. The top is a bit lower, but definitly within proper specs. Not positive, but I'm pretty sure it piston/cylinder walls were scored or bad rings you would be seeing a much bigger difference. (75psi vs the other two @ 160) A decarb (see engine FAQ) might bring that top cylinder up a few pounds if the rings are stuck.

My manual isn't here yet any idea what the spec is for # readings?

 

[Laddies]

Re: 74 Mercury 650 Rebuild or no??

Mercury was not concerned with compression as long as it was 120 and within 10%. Your engine originally had a timing decal on the flywheel, I don't know where you could find one so I think you will have to mark the flywheel at TDC and again at 23 degrees. Here are some pictures, in some you will see the timing indicator installed in the block I think you will have to make something that will replace the factory one inless you can find one on a donor engine or a old Merc mechanic that will part with one. Hope this helps.

 

[bnold]

Re: 74 Mercury 650 Rebuild or no??

Thanks for the response! Well I am well above 120 so I guess I going to leave the block alone..

Going to order my gaskets and rebuild kits this week, thanks for the help. You answered my question on the flywheel... Just wasn't sure if it was weighted or something to require being lined up a special way.