Bad coupler? 1995 Mariah Talari 4.3L Alpha One
 

Hi Guys,
I just took my 1995 Mariah talari Z200 out today...Just put in a new prop (Alpha 4.3L) engine run, boat goes about 5 mph at full throttle...rpm@3000, Oil pressure @40psi and engine Temp under 100 deg. , is it a spun a coupler? Would thought it over heat or it would give out burning smell, but i did not experience niether. Sometime, if i reset the throttle and speed up slowly...it would speed up fine..

Re: Bad coupler? 1995 Mariah Talari 4.3L Alpha One
 

Spun prop hub would be my guess on that one.

Re: Bad coupler? 1995 Mariah Talari 4.3L Alpha One
 

new prop with new hub.

Re: Bad coupler? 1995 Mariah Talari 4.3L Alpha One
 

If the coupler is shot, you should get some smoke and burning smell in the engine compartment when it's slipping.

Was the prop a rebuilt unit? Might check the hub carefully for evidence of it being spun. Sometimes can be hard to see that.

If no evidence of spun coupler or hub, maybe check to see that you aren't missing on a cylinder or 3. Pull plugs and make sure they all look the same (color and burn). A bad plug, wires arcing, or weak spark from the dizzy could cause symptoms similar to what you're describing.


When was the last time the boat ran? Did it plane out ok then?

Is the new prop the same size and pitch as the one it replaced?

Re: Bad coupler? 1995 Mariah Talari 4.3L Alpha One
 

I do believe he already fixed the issue with a new prop & hub kit.

Re: Bad coupler? 1995 Mariah Talari 4.3L Alpha One
 

To find out which it is, a Merc mechanic of 26 years told me to do this:
Put the boat in gear ("not while it's running of course," he said that)
Go stand on one of the prop blades

If the shaft spins with the prop, it's the coupler
If the prop spins on the shaft, it's the hub

If it's just the hub there's no reason to replace the entire prop assembly. A prop shop can press a new hub into the old prop.

Re: Bad coupler? 1995 Mariah Talari 4.3L Alpha One
 

It was doing that at the end of last season, so i bought a new prop which came with a new hub. I was thinking it might be a cylinder too....cuz there aren't any smoke /smell and the temp is normal. It's hard to start and it would only goes up to 3000 rpm.

ps... i put it in gear, it spin freely clockwise but lock counter clockwise.

Re: Bad coupler? 1995 Mariah Talari 4.3L Alpha One
 

Where are you located?

A new coupler isn't too bad to put in...maybe 3 or so hours...I've had motors in and out of my Mariah nearly a dozen times.

I think a compression test might be in order...although even if it is turning 3000 rpms it should still be turning the same speed as it was before. Doesn't matter how much power is there, if it's spinning 3000rpm then your prop will turn at the speed determined by your gear ratio, unless something between the flywheel and the prop is no good. No clunking or knocking so I wouldn't suspect ujoints or gears, sounds like a coupler to me. Real easy to pull the drive leg to check.
Put it in Forward gear
Remove pin that connects trim rams to outdrive
6x 5/8" nuts, disconnect speedo-hose, pull the drive free. Might need a large flat blade to separate it from the gimble housing.
Check the splines on the drive shaft input, and shine a flashlight inside to determine condition of internal mating splines. If your coupler is shot you probably will have some metal chunks/flakes on your driveshaft.

Re: Bad coupler? 1995 Mariah Talari 4.3L Alpha One
 

Check the easy things first though. Pull the plugs, see how it's burning. There's photo comparisons online that will explain each type of burning condition. Next, Spark plug tester, check each ignition wire. Spark present at all 6, compression test.

Re: Bad coupler? 1995 Mariah Talari 4.3L Alpha One
 

Thanks guys! I wasn't able to pull the boat out at all last year and this summer. I finally pull it out last month to trouble shoot again, one of the spark plug was crack. I replaced all the plugs, all is well!

Thank you!