High RPM’s

[spinbp5]

Hello one and all,
I have an 1994 Glastron with a mercruiser mcm 3.0L/LX, DEIS, 4 cylinder, displacement 181 CID, LH engine rotation, WOT RPM 4400-4800. TRANSOM Alpha One Power Trim XD 1.98R, standard rotation.
I just replaced the carburetor and made the necessary adjustments and it idles great when not in forward or reverse motion. However, when I go into forward motion the RPM’s are so high and the boat will not pick up speed. I honestly do not believe that the carburetor is any factor as I’ve made adjustments before and during forward motion.
I’d be grateful to get anyone’s input on this issue.
Thank you so much,

 

[spinbp5]

Correction on the rotation: It is RH.

 

[ScottinAZ]

if you are advancing the throttle, and the engine picks up speed, but the boat doesnt go any faster, start looking at the coupler and the prop hub.

if the engine does not advance in rpm with increased throttle, then the accelerator pump in the carb may not be functioning. If you used an "Amazon special" replacement carb, they are somewhat known to be junk right out of the box. If its a "good brand" carb, start checking with the manufacturer/rebuilder for your options. Any of the original carbs are around 30 years old at this point, so some fiddling is almost to be expected to get them working right.

 

[alldodge]

^^^Agree, coupler or prop hub

Does the boat actually move forward when shifted in forward?

Read your other thread, (sorry didn't notice it sooner) and when the motor was replaced the shop should have checked and adjusted alignment. If they didn't then this may have caused the coupler failure

Take a grease pencil or other marker and mark the prop hub. Run it in the water for short time and check if mark moved

 

[Bondo]

Correction on the rotation: It is RH.

Ayuh,..... Welcome Aboard,....... Yer lookin' at the wrong end of the motor,......
Rotation is determined at the flywheel end,....
Pretty much all of our motors are lefthanded,......

 

[spinbp5]

if you are advancing the throttle, and the engine picks up speed, but the boat doesnt go any faster, start looking at the coupler and the prop hub.

if the engine does not advance in rpm with increased throttle, then the accelerator pump in the carb may not be functioning. If you used an "Amazon special" replacement carb, they are somewhat known to be junk right out of the box. If it’s a "good brand" carb, start checking with the manufacturer/rebuilder for your options. Any of the original carbs are around 30 years old at this point, so some fiddling is almost to be expected to get them working right.

Hey thanks for your input…Yes, exactly what I’m dealing with. I put in forward motion and it definitely picks up rpm’s but the boat just won’t advance accordingly. When I push forward I hear something like a cling, cling, cling and upon advance forward it stops and the boat moves forward. The boat however does not advance with the forward motion of the throttle. I can rev it all the way forward and the boat stays at the same speed with no advancement. I was thinking it might be the prop and hub. I took the boat out today and after about 15 min of going about 5mph I felt a big thud at the rear of the boat. I pulled it out of the water noticed that one of the fins on the prop broke off. So I’m going to buy a new prop and hub.

 

[spinbp5]

^^^Agree, coupler or prop hub

Does the boat actually move forward when shifted in forward?

Read your other thread, (sorry didn't notice it sooner) and when the motor was replaced the shop should have checked and adjusted alignment. If they didn't then this may have caused the coupler failure

Take a grease pencil or other marker and mark the prop hub. Run it in the water for short time and check if mark moved

Yes it does but only goes bout 5mph. I took it out today and after bout 15min, I felt a big thud in the rear and lifted the prop up and noticed a fin on the prop is missing. So I’m going to buy a new hub and prop.

 

[alldodge]

There was no mention of smelling burnt rubber, so it's most likely the hub

 

[ScottinAZ]

Hey thanks for your input…Yes, exactly what I’m dealing with. I put in forward motion and it definitely picks up rpm’s but the boat just won’t advance accordingly. When I push forward I hear something like a cling, cling, cling and upon advance forward it stops and the boat moves forward. The boat however does not advance with the forward motion of the throttle. I can rev it all the way forward and the boat stays at the same speed with no advancement. I was thinking it might be the prop and hub. I took the boat out today and after about 15 min of going about 5mph I felt a big thud at the rear of the boat. I pulled it out of the water noticed that one of the fins on the prop broke off. So I’m going to buy a new prop and hub.

with the "cling cling cling" noise also check your shift cables to ensure the drive is actually going into gear. You can get that noise if the dog clutches are not fully engaging if the shift cables are faulty. THIS IS VERY DAMAGING TO THE DRIVE.... so check it sooner rather than later.

 

[spinbp5]

with the "cling cling cling" noise also check your shift cables to ensure the drive is actually going into gear. You can get that noise if the dog clutches are not fully engaging if the shift cables are faulty. THIS IS VERY DAMAGING TO THE DRIVE.... so check it sooner rather than later.

Will definitely do that, thanks for your insight.