omc model numbers

[hefty67]

can anyone help i need to find out what kind of outdrive i have the nameplate says model#983041 and the serial# t0427090 any help would be great ,thanks

 

[KaGee]

Re: omc model numbers

Sure you have the right number???<br /><br />Anychance your engine still has a model # tag still on it??

 

[hefty67]

Re: omc model numbers

the tag is on the lower unit. and the outdrive is not the original one for the boat also it is a 13 spline shaft

 

[hefty67]

Re: omc model numbers

im sorry it is on the upper housing behind the trim ram

 

[Boatin Bob]

Re: omc model numbers

The fact that you have trim rams says it's a Cobra drive. What info do you need? What size is the engine?

 

[hefty67]

Re: omc model numbers

the engine is a 7.5 (460 340hp)i tried to get a prop for this thinking it would be a 800 king cobra because the trim rams say king cobra but the spline is 13 tooth.the prop wont work it is a 14.5x18 the diameter is to big so i need to know what the outdrive is and is the gear ratio ok and will it handle the big block hp? i am thinking it is a 400 but dont know. thanks

 

[Boatin Bob]

Re: omc model numbers

OK it won't be an 800 drive it will be a King Cobra with the 460, they used these from 1987 to 1990. If you look on the thermostat housing or if you have the square plastic cover on the flame arrester you should see a model/sn sticker for the engine. Even though these were called King Cobra's they still had the clutch dog lower unit until 1990 when they went to the cone clutch. I' don't understand what you mean by the diameter is too big on the 14.5 prop? These drives will take a 15 in prop because I have 2 of them in my boat and run 15 x 17 SS props.

 

[hefty67]

Re: omc model numbers

the prop is hitting the top of the lower unit where the anode bolts and also the hub of the prop hits the outer housing of the prop shaft. i dont know how to send pics so i can show you.

 

[Boatin Bob]

Re: omc model numbers

There is no anode up there for the prop to hit, do you mean the adjustable trim tab? Have you had the prop off, there needs to be a big thrust washer on the shaft in front of the prop otherwise it will go too farward on the shaft and hit the housing.

 

[hefty67]

Re: omc model numbers

yes the trim tab, how thick should the washer be?

 

[Boatin Bob]

Re: omc model numbers

It's a big washer with a lip on it so it actually sits in the front of the hub housing on the front of the prop. I would say it probably is at least 1/8 or 3/16 thick. If there is some grease it can actually stick to the front of the prop when pulling it off so some people don't even see it unless they know it's there.

 

[hefty67]

Re: omc model numbers

thanks for the help the outdrive must be wrong for my boat it has 13 splines and i can only a 14" prop without hitting the zinc adjustable trim tab and the prop hub is bigger then the outdrive hub

 

[Boatin Bob]

Re: omc model numbers

Sounds like someone might have put a regular Cobra drive on there which isn't good. OMC built the bigger beefier Cobra drive specifically for the big block to handle the extra power/torque. I think the upper is the same (different gear ratio) but the lower was actually borrowed from their 300 hp outboard. A regular Cobra holds about 64 oz of gear lube and the bigger ones take 108 oz.

 

[rbezdon]

Re: omc model numbers

This is a good theory but my regular Cobra takes a 14.25x19 prop just fine. He is hitting the trim tab with a 14. Maybe the trim tab ahs been replaced incorrectly.