Help identifying my outdrive?

[davesissom]

Hello
My old outdrive needed alot of work and I was able to find a replacement off of a different boat with the same motor (OMC 4.3) The replacement was rebuilt three years ago with all new parts and runs great. But my old prop was bent and the replacement came with a prop. I can't get my boat to go on plane now unless I am by myself. The old outdrive and old prop would plane easy with six people. I hope it is a prop problem but I need help finding out which drive I have. My boat is 1990 and I was told the drive is a year or two newer, the ID plate on the side is missing, only a cobra sticker on both sides. Gear ratio should be the same right? Since both engines were 4.3 OMC? I have tried aluminum cupped 14 x 17 and stainless 12.75 x 23. Both do about the same with a loaded boat. 4400 rpms nose in the air moving about 9 mph. The boat will plane and go faster with just me but still no where near what it used to. Need help! Prop??? Or something else???? Engine runs great, boat doesn't leak. 18 1/2 ft bow rider. Will try to post pics of outdrive. Thanks

 

[Boomyal]

Re: Help identifying my outdrive?

4400 rpms and 9 mph? Do you have a sea anchor out? :laugh: That just does not sound right, almost as if something is slipping to allow the motor to reach that RPM but not move the boat.

 

[davesissom]

Re: Help identifying my outdrive?

4400 rpms and 9 mph? Do you have a sea anchor out? :laugh: That just does not sound right, almost as if something is slipping to allow the motor to reach that RPM but not move the boat.

Another picture. It just seems to me that at least one of the props would have got the boat on plane.

 

[Boomyal]

Re: Help identifying my outdrive?

Well if you think you have a prop size issue, or even possibly a slipping hub, you should post in the prop section. I have no clue what props Cobra's use.

 

[HT32BSX115]

Re: Help identifying my outdrive?

Another picture. It just seems to me that at least one of the props would have got the boat on plane.

Howdy,


well, it's not a prop issue yet!

do you know what the drive ratio is?

if not, pull the spark plugs and have some one count blades (in FWD) while you turn the crankshaft with a wrench.

You should have a 1.68:1 ratio (or very close to it for a 4.3L V-6)

If the engine is REALLY turning 4400 RPMs at 9 mph, you either have a bad tach, or a spun hub or coupler.

If it's the latter(hub or coupler) , it won't last long. If it's the hub, change props and see if it still does it.

If it's the coupler, you'll be removing the drive and engine (in that order) soon.

 

[davesissom]

Re: Help identifying my outdrive?

Thanks guys for the reply, my shop manual says its a 1.68 ratio, what is a coupler? And should I try the old prop to illeminate the prop question even though its bent? It runs good other wise, doesn't feel like its slipping and don't notice any unusual noise, runs alot quieter and smoother than with the old outdrive, seems to be giving the prop plenty of power it just won't get over the hump. Thanks, Dave

 

[davesissom]

Re: Help identifying my outdrive?

The boat ran like a champ before the new outdrive, the reason for the change was the slip-clutch shift cable issue and while apart noticed the bearings were on the edge of spec. Has new shift cable, bellows, gears and bearings 3 years ago. I just don't understand why the old outdrive that was messed up worked better than the new one other than different props. Thanks, Dave

 

[HCMQA]

Re: Help identifying my outdrive?

Yes put on the old prop and try it.
The coupler is what is attached to your engines flywheel and the drive shaft from the out drive goes into it.
Without the id plate on the drive you have no idea what ratio you have.
It really does sound like you have the incorrect ratio.
A 17" pitch should have you popped right out of the water. I have a 19" on my 4.3 w/cobra and it gets on plane instantly.

 

[HCMQA]

Re: Help identifying my outdrive?

Oh and I am not sure what you mean by a slip clutch? There is no such thing in a cobra.

 

[Four Winns Erie]

Re: Help identifying my outdrive?

I have the same setup and my prop is 19 x 14 1/2. I get on plane in a couple of seconds if alone in the boat. My ID plate doesn't look like it would come off easily and it's a couple of years older than yours. Is it possible it was removed intentionally to deceive you?

 

[davesissom]

Re: Help identifying my outdrive?

I am not sure why it would have been removed. The mechanic gave me a 45 day warranty on the replacement drive so I don't think it has anything to do with trying to deceive me. I just can't figure out why it ran so good with the old drive that needed so much work done to it? And the slip clutch I think is also called the dog clutch. If the problem is the coupler the old drive would have had the same problem getting on plane right? Thanks

 

[HT32BSX115]

Re: Help identifying my outdrive?

If the problem is the coupler the old drive would have had the same problem getting on plane right? Thanks

Yes. unless it has just failed. And if it has, it will completely fail quickly.

Thanks guys for the reply, my shop manual says its a 1.68 ratio

That of course does not make your drive a 1.68:1 ratio. After all these years it could be anything (unless you bought it new) .....AND unless they verified it, you will not know unless you pop the top off and count teeth or turn the input shaft and count turns on the prop shaft. (let me add that the wrong ratio would NOT cause your speed to be 9mph and your RPM 4400!!)

If you have a "slipping" dog-clutch, you better plan on getting your "45 day warranty" validated, because the "damage" is already done.

If it's a prop hub, which is fairly common, trying a different prop will verify that.

If you have a service or owners manual and an accurate tach you can select the correct prop pitch by running the boat at WOT (Wide Open Throttle)

The engine should turn maximum (top of the MFR's recommended range) RPM at WOT with the boat lightly loaded.... 1/2 fuel, 2 people etc.......

Use a prop slip calculator to determine what the approx boat speed should be.............. Prop Slip Calculator ..............Use 15% slip (common for single prop drives and planing runabout boats.)

 

[davesissom]

Re: Help identifying my outdrive?

Ok thanks will try, the "slipping" dog clutch was on the old drive and that's how I came to own this one. Starting to wish I would have just rebuilt the old drive, at least I would know exactly what I have.

 

[boaterinsd]

Re: Help identifying my outdrive?

i bought a rebuilt one last summer off a guy on ebay and hes got the tag on it with the ratio and info.

 

[davesissom]

Re: Help identifying my outdrive?

ok just got back from the lake with 2 new props to try from mechanic. 14 x 19 3 blade and 14 x 21 4 blade. Both props got on plane with only 2 in the boat, slowly. I don't think it would ever plane with a loaded boat or a tube. Not a prop issue? I don't think coupler or hub because it has been ran app. 4 hrs on and off with this problem. And will still plane with a light load. The old outdrive had a 15 slpine and the new has a 13 spline. I think something internal is going on. Mechanic wants to take to the lake with a tach and see what its doing for himself and is offering to just rebuild the old drive. Any other ideas. could the spline difference offer any info as far as a different gear ratio?? Both came off a 4.3.??? Where are the different ratios located, in the top or bottom of the outdrive??? The old drive had the impeller in the bottom and the new one is about half way up on the back?? Are these totally different outdrives???

 

[HT32BSX115]

Re: Help identifying my outdrive?

ok just got back from the lake with 2 new props to try from mechanic. 14 x 19 3 blade and 14 x 21 4 blade. Both props got on plane with only 2 in the boat, slowly. I don't think it would ever plane with a loaded boat or a tube. Not a prop issue?

With a 21p 4 blade prop, your boat would go approx 50 mph at 4600 and about 45 with the 19p. but only assuming it has a 1.68:1 drive.....

You didn't post an RPM so it's difficult to know what performance you're really getting.

Where are the different ratios located, in the top or bottom of the outdrive???

It's not stamped on the drive nor would it be based on the serial number of the drive by now since the drive could have been rebuilt many times in it's life with different gear-sets.
This should help. I don't remember what years the below picture came from. but it doesn't matter. turn the input shaft and count prop shaft turns and you'll know for sure.

If you had a failed coupler, you wouldn't go anywhere by now.

If it was a prop hub, you proved that wasn't the problem by replacing the prop.

I am beginning to think your engine is either seriously worn out or the timing is seriously "retarded"

 

[davesissom]

Re: Help identifying my outdrive?

The engine only has 500 hrs on it and has been well maintained. I cant try the old prop because it was a 15 spline and the new drive has 13 splines, starting to think this is my problem. Mechanic is rebuilding the old outdrive today and we will see if that fixes the problem.

 

[Levinz11]

Re: Help identifying my outdrive?

Pretty sure the 13 spline Cobras were hitched to the 2.3 and 3.0 engines. Sounds like you found your problem.

 

[davesissom]

Re: Help identifying my outdrive?

I sure hope so. Boats aren't much fun when they don't work right. Thanks for all the advice and tips, I will post results when the old drive is installed and can hit the water. Thanks, Dave

 

[boaterinsd]

Re: Help identifying my outdrive?

so whats new with the boat? Have you got it figured out?