OMC 3 cyl Questions

[rekcuftar]

Can someone who has a store of off the cuff knowledge regarding the OMC 3 cyl PM me there number so I can pepper them with a bunch of questions.

[CRMERC]

how many questions are we talking about?

[rekcuftar]

My current setup is a 13ft runabout with a 1978 20" Stinger.

1. Barely able to get on plane with a 13x19 prop. I have the large lower unit 2.4:1. Am I over propped or do I have a low speed jet or other issue? (Should I be trouble shooting or re-propping)

2. What is the difference between a the nitro and a 2cyl lower unit? Is there any? If its internals can they be swapped in?

3. Is there a year of 56 cube power head that would fit the rest of my setup? If so what? I think FastFred mentioned that certain years of carbs had a mid as well as low and high jets what years.

4. What props would you recommend for my boat. 1. To go fast? 2. To carry 2 adults? 3. To pull a small kid on tube or ski's?

[CRMERC]

19 pitch should not slow down a 70 on a 13ft bullet? has a 17p on my 16 ft runabout and it planed off no problem. are you sure it is lit on all cylinders?

[rekcuftar]

The motor seems to run well once it get on plane, but is very slow to lift the boat out of the water. When I first got my motor back the shop ran it for me in tank and it seemed to run fine. When I got to the lake it would start and rev in neutral but quit when put in gear. I took it back and they determined one of the low speed jets was bad, also some plastic shavings in carb bowl that they suspected came from my new plastic moler tank. They trouble shot and fixed it at no charge. They have also been very helpful even borrowing me tools. But now I am wondering if another low jet was bad and not caught or if a jet is clogged with some of more of my new tank or other stuff. It just doesn't seem likely that I am over propped with what some other rigs are running.

[Mr.Rude]

My current setup is a 13ft runabout with a 1978 20" Stinger.

1. Barely able to get on plane with a 13x19 prop. I have the large lower unit 2.4:1. Am I over propped or do I have a low speed jet or other issue? (Should I be trouble shooting or re-propping)

2. What is the difference between a the nitro and a 2cyl lower unit? Is there any? If its internals can they be swapped in?

3. Is there a year of 56 cube power head that would fit the rest of my setup? If so what? I think FastFred mentioned that certain years of carbs had a mid as well as low and high jets what years.

4. What props would you recommend for my boat. 1. To go fast? 2. To carry 2 adults? 3. To pull a small kid on tube or ski's?

1. Prop may need to vent some to get the rpm up for faster planing. Try drilling vent holes in prop.
2. Nitro and 2 cyl share same housing style/size, but nitro has 1.86:1 gears and the 2 cyl has 2.42:1
3. The powerheads should interchangeable to each other, the bore specs are larger on the 56's matching the big hp 2 cyl motors to give the extra cubes. Not sure on the other differences in the blocks or carbs though.
4. I would try a small pitch SRX as a start.

[rekcuftar]

The Prop has holes drilled at the base of each blade currently. I could drill them larger or change to a different pitch or have the prop reworked a number of ways. The big question is, is my propeller the issue or the motor. Can anyone running a similar rig offer an opinion?

With respect to the gear case, what years 2 cyl shared the cases with small 3 cyl foot? Can new gears still be had for this case? or does someone have a extra small diameter case they are trying to unload?

On the 56 cub power head. Is there a year that would fit my cowl and pan? I would love to graft a 56 cube to my current mid and lower and keep the old stinger look? If so what years?

And what pitch is a "small pitch srx"? You need to talk loud and slow to me I'm mechanically curious but challneged.

[mr_velocity]

I run basically the same setup with a few differences.
I run a shorty mid on a yamaha pro 50 bracket, gets me trim/tilt with the short mid.
Getting on plan is sluggish until the prop vents and I build some rpms. The boat is heavy so its expected. Once I get over 2500 rpm she builds stump pulling power really quick.
I've blown a few lowers, always gone with the 2cyl cases since they are cheap on ebay. Usually just need to change the shaft/shift for my 15" mid. Again, if you're having problems coming out of the hole then you'll want the 2cyl case with the 2.42:1 gr. If you're having problems now with the steeper nitro gr you'll never be able to build the power.
Only prop that I could get to hook up and give me the performance I was looking for was a 4 blade SS, Rich Junker said it looks like a mini drag prop. He definitely worked some magic on the prop.
Can run more vertical lift with a nose cone lower, have both.....well Fast Fred has one but when he's done building the case I'll give it a shot.
I spin my motor to 7600 rpm.

[rekcuftar]

Mr. Velocity you'd guess that I am probably over propped rather than have motor issue? I was hoping to hear the other because I think I could prop higher on the top end.

What pitch and ratio do you run currently?

Love your boat I have been looking at it with covetous eyes for more than a year. The Funcat was one of the boats I was hoping to snag but this deal came up first. I think you have the nicest small boat on the board.

Here's and old Funcat Vid I ran across.

http://www.youtube.com/watch?v=Pnji_ZnF2Dk&feature=fvst

[mr_velocity]

Mr. Velocity you'd guess that I am probably over propped rather than have motor issue? I was hoping to hear the other because I think I could prop higher on the top end.

What pitch and ratio do you run currently?

Love your boat I have been looking at it with covetous eyes for more than a year. The Funcat was one of the boats I was hoping to snag but this deal came up first. I think you have the nicest small boat on the board.

Here's and old Funcat Vid I ran across.

http://www.youtube.com/watch?v=Pnji_ZnF2Dk&feature=fvst

Cool vid!!!

The prop is a 19. I have the same prop in a 20 but I need to have it worked before putting it on the boat. I'm running the stock 2cyl 2.42:1 gear ratio.

I started with the nitro case with the steeper gear ratio, though I had motor problems and spent a lot of my and Fast Fred's time trying to get it sorted out. Once I changed lowers to the 2.42 it solved my problems. A over the hub exhaust prop may help you get on plane.

[HPShadow]

the stock gear case should work try a difrent prop watch yourmotor hieght and set back since thats a littlle diffrent then the original bullets whats the set up of the boat tank location batt all the weight in the rear wont help u plane off i run a 17p prop on a 70 johnrude.

[ChrisCarsonMarine]

Exhaust outlet Is different between large and small bore 70's,as well as drive shaft splines,won't work.70's are famous for being weak at take off but run well at speed due to low compression,check it.

[99fxst99]

I had this problem with a 75 Stinger on a SE boat I flipped many years ago. Found out, after many hours of trying everything, that the trigger was frozen and would not advance,Freed it up and the motor ran fine.

[rekcuftar]

the stock gear case should work try a difrent prop watch yourmotor hieght and set back since thats a littlle diffrent then the original bullets whats the set up of the boat tank location batt all the weight in the rear wont help u plane off i run a 17p prop on a 70 johnrude.

Because of the lift I am now 3 7/8 back. I have a 6 gallon under the nose and have since moved a 15 lb battery 9 ft forward. It's made huge difference and now it gets on plane much faster.

Are you running the 17p with the nitro or v4 gear case?

[rekcuftar]

Exhaust outlet Is different between large and small bore 70's,as well as drive shaft splines,won't work.70's are famous for being weak at take off but run well at speed due to low compression,check it.

I was thinking one of the earlier like 86 to 89 56's might have the same coarse spline? Would that bolt up or is there other issues that I am not thinking of? Would it work if I took the adapter and tuner from late 80's 56er?