How hard is getting and replacing this old belt going to be?

[softdown]

Mercury Mark IV Thunderbolt 40hp.....1957. My shop manual is 13 miles away at a closed post office.

Motor last started 8 years ago. Showed a glimmer of interest in catching three times. Only has 20% of full range in throttle cable. Choke closes about 50%.

Mission Impossible?

 

[racerone]

All the Mercury motors with a belt driven distributor used the same belt.---Up to the mid 1970 models.----Any good boat shop would have it in stock.Your shop manual would explain the easy steps to change / line up the belt.

 

[softdown]

All the Mercury motors with a belt driven distributor used the same belt.---Up to the mid 1970 models.----Any good boat shop would have it in stock.Your shop manual would explain the easy steps to change / line up the belt.

Sounds like my distributor will now be grossly out of timing, however you say it is easy to line up. I live in the highest desert in the world, there are no boat shops to my awareness. Hence my leaning towards mail order. Distributor belt?

 

[Scott Danforth]

If youre in the highest desert in the world. Do you need a boat? LOL

 

[racerone]

??-------The belt is easy to order.-----in stock in many places !

 

[merc850]

Try turning that pulley first - if it doesn't turn you will have to replace the dist bearings, the belt could have broken because of seized bearings; you'll also have to remove the flywheel which might be difficult. You should take the whole dist assembly off and clean it. What's the ser Nr.? Here's a company that supplies parts http://store.oldmercs.com/category_s/676.htm. This motor looks like it's in rough shape I would do a compression test also to see what's up.

 

[softdown]

If youre in the highest desert in the world. Do you need a boat? LOL

As you see in my sig, the goal is liveaboard a boat for awhile. Water is often more fun.

 

[softdown]

Try turning that pulley first - if it doesn't turn you will have to replace the dist bearings, the belt could have broken because of seized bearings; you'll also have to remove the flywheel which might be difficult. You should take the whole dist assembly off and clean it. What's the ser Nr.? Here's a company that supplies parts http://store.oldmercs.com/category_s/676.htm. This motor looks like it's in rough shape I would do a compression test also to see what's up.

Reckon a compression check is always a good idea. Agreed that it looks rough in the photo, I was generally happy with its overall looks. A busted up belt will make most any motor look very rough. However...seized bearings and flywheel removal might make me forget this project for awhile. I'll check tomorrow since the motor is buttoned down for weather right now.

There is some curious surface rust on the top.

 

[softdown]

The distributor pulley turns very easily. Are belts supposed to last over 60 years?

 

[softdown]

Cylinders 1, 2 and 3 all tested out with identical compression of 85 per my fairly cheap gauge. Was not able to test #4 due to an overly tight bend that I did not overcome.

I feel the extreme uniformity of compression is encouraging. No idea what new compression would be. Or if my gauge is very accurate.

 

[merc850]

I have 60 yr. old belts that are OK but I always replace them for security. 85 is fairly good.

 

[softdown]

I have 60 yr. old belts that are OK but I always replace them for security. 85 is fairly good.

Seems to be a fair guess that they were unable to start it due to slipped belt. If the belt is the only problem, I feel like I did very well for $100 incl. an old 14' fiberglass runabout. The boat likely has almost no value. The trailer has some though I had to put tires and wheels on it. Both lights work if I press on one bulb just the way it likes it. Other side is fine.

This may be a kick *** dinghy for my sailboat, pretty fast dinghy with good cargo capacity. I'll have to attach some inflatable material so the dinghy is more "unsinkable".

Would 100 be excellent compression? Seems that automobile compression runs higher...

What is the value of an outboard that will not start? I see plenty for sale. Seems like a guy with carb skills could make some money. Also seems like a buyer should always do a compression test unless buying around scrap value.

What is scrap value of outboards? Thanks for the patience...

 

[softdown]

What tool is required to remove the flywheel?

I have worked with car engines and some small engines like rota-tillers. Boat engines are much more difficult in my opinion.

The shop manual covers all Merc engines up to 1965. It is confusing for the do-it-yourselfer.

 

[softdown]

Takes a three legged puller using 1/4" bolts on the vintage Mercury's. I can't find mine of course.

 

[racerone]

Flywheel is usually pulled using that big internal thread near the flywheel nut.----And why do you want to pull the flywheel here.-----This motor may start with a cleaning and setting of the points in the magneto.---Set them at 0.010".-Also clean carburetors.----Once motor shows promise you can do more preventive maintenance.----Belt and impeller etc.

 

[merc850]

Bolts are 3 - 3" x 1/4" x 26 tpi. make sure that the bolts are threaded in as far as you can and maybe pour some penetrating oil first then tighten the puller tight and wait.

 

[GA_Boater]

The flywheel needs to come off. No way to R & R the belt and it won't run with out the belt.

I pulled mine with regular puller. Wish I forked out the 30-40 bucks for the right one Ebay, it makes it so easy.

 

[softdown]

Flywheel is usually pulled using that big internal thread near the flywheel nut.----And why do you want to pull the flywheel here.-----This motor may start with a cleaning and setting of the points in the magneto.---Set them at 0.010".-Also clean carburetors.----Once motor shows promise you can do more preventive maintenance.----Belt and impeller etc.

The flywheel must be pulled to install a new belt. I think the belt is what retains proper timing. The flywheel has a marking for top dead center and a marking for before top dead center.

 

[softdown]

The flywheel needs to come off. No way to R & R the belt and it won't run with out the belt.

I pulled mine with regular puller. Wish I forked out the 30-40 bucks for the right one Ebay, it makes it so easy.

Ebay shippers send it yesterday when there is no rush. Slow boat from China when I need to get things done it seems.

 

[racerone]

Maybe I should look at the 6 or more of these magneto equiped motors in the shed to see how it all works !!