Help With Troubleshooting from all You Professionals

[Night Watch]

I recently built and installed a new atomic-4 engine in my 30' Catalina. A great experience that I've enjoyed. I took the boat out today for the first time under power.
ISSUE: propwash in forward gear at all RPMs isn't near what it was prior to installing the new engine. I don't sense any or very little feedback in the tiller while underway either, nothing like what I used to get with the old engine (which was coming off its mounts).
I DO have forward thrust but appears to be less than optimum.

It's not the engine. The engine is putting out over 3000 rpm and it's a direct drive powertrain.
I've run the engine in forward gear tied to the dock several times.

It's been nearly 6 months since I started the removal/installation of this engine. So, the boat has set in the slip for a while now. But I have the hull cleaned every other month. So, surely, it's not a fowled prop, or is it?

The only thing I did to the power train was disconnect it from the engine and then reconnected it after the installation.

I'm thinking it could only be one of three things: prop is fowled, prop shaft engine coupling is slipping, or the propeller is stripped/stripping on the shaft.

When I reconnected the prop shaft to the engine, I pulled the shaft forward until it was up against the cutlass bearing and then repositioned the engine to within 0.005" and aligned it and bolted it down.

Anyone else have any ideas before I start my troubleshooting?

 

[dmax]

I would say a fouled prop is the most likely culprit. The engine coupling shouldn't ever slip, if it did, you'd probably hear it. If the prop was slipping you'd probably have no thrust at all.

 

[Night Watch]

I would say a fouled prop is the most likely culprit. The engine coupling shouldn't ever slip, if it did, you'd probably hear it. If the prop was slipping you'd probably have no thrust at all.

Occam's Razor: simplest answer is most often the correct answer.

 

[kappykaplan]

I would say a fouled prop is the most likely culprit.

 

[JoeWhite]

A clearance of 0.005" is much too little. Prop may be rubbing against the strut and causing load on the engine. Can you put a few washers between the coupler and transmission and try it that way for test?

 

[Davidasailor26]

Prop may be rubbing against the strut and causing load on the engine.

I agree. The prop shouldn’t really be up against the cutless. I’m used to seeing about 1” gap there. Having said that, if the engine is still getting to the right RPMs my guess for reduced thrust is still a fouled prop.

 

[jssailem]

ISSUE: propwash in forward gear at all RPMs isn't near what it was prior to installing the new engine. I don't sense any or very little feedback in the tiller while underway either, nothing like what I used to get with the old engine (which was coming off its mounts).
I DO have forward thrust, but it appears to be less than optimum.

What type of PROP?
You say there is "forward thrust, but it appears less than optimum"

• What is Optimum at 3000RPM
• Why would you expect PropWash? Not all props create propwash. Saying that, I do not see how a new engine would affect propwash when all the rest is the same. Yet it is not the same. You pulled the prop up against the strut. The prop is sitting in a different place than before. You may also have moved the prop closer to the bottom of the hull. This will affect the water between the hull bottom and the vortex (disturbed water) from the blades of the prop. This could impact the propwash.

 

[heritage]

Do you notice a reduction in prop wash and speed in reverse? If not, I would suspect the prop being forced into the cutlass bearing when in forward.

 

[Night Watch]

A clearance of 0.005" is much too little. Prop may be rubbing against the strut and causing load on the engine. Can you put a few washers between the coupler and transmission and try it that way for test?

That's a good idea! After a visual inspection of the prop, if it doesn't appear to be fouled then I'll try a spacer.

 

[Night Watch]

Do you notice a reduction in prop wash and speed in reverse? If not, I would suspect the prop being forced into the cutlass bearing when in forward.

I'm getting reduced prop wash in both directions.

 

[Night Watch]

What type of PROP?
You say there is "forward thrust, but it appears less than optimum"

• What is Optimum at 3000RPM
• Why would you expect PropWash? Not all props create propwash. Saying that, I do not see how a new engine would affect propwash when all the rest is the same. Yet it is not the same. You pulled the prop up against the strut. The prop is sitting in a different place than before. You may also have moved the prop closer to the bottom of the hull. This will affect the water between the hull bottom and the vortex (disturbed water) from the blades of the prop. This could impact the propwash.

Today I could only manage 1.5-2knts in forward while running at 2200-2500RPM. Barely enough headway to overcome the prevailing wind.
I have a 3-bladed Indigo aftermarket prop (see attached photo). As for your comment on the prop "up against the strut" Last summer's haul out the prop was "up against the strut" I "attempted" to position it where it should have been before the engine replacement. If it isn't, the prop can't be more than 2-3mm from it's intended location.
I expected PropWash from past experience in this boat, there was a lot and feedback in the tiller due to it.

 

[Night Watch]

I agree. The prop shouldn’t really be up against the cutlass. I’m used to seeing about 1” gap there. Having said that, if the engine is still getting to the right RPMs my guess for reduced thrust is still a fouled prop.

Fouled prop Hoping! But I think I've made a mistake of mounting the engine where the prop is too far forward by a "hair". But we're talking about millimeters in distance from before the install, so I don't see how this would have such a dramatic effect on my boat's headway speed.

 

[Night Watch]

A clearance of 0.005" is much too little. Prop may be rubbing against the strut and causing load on the engine. Can you put a few washers between the coupler and transmission and try it that way for test?

This 0.005" is the tolerance from side to side for alignment of the engine to the prop shaft. The Catalina manual calls for a 0.003" tolerance when aligning prop shaft. So, once I confirm there's no fouled prop I plan to add some standoff and see it that changes things.

 

[JoeWhite]

When I reconnected the prop shaft to the engine, I pulled the shaft forward until it was up against the cutlass bearing and then repositioned the engine to within 0.005" and aligned it and bolted it down

By saying cutless bearing I believe you meant prop shaft coupler.
But in any case, the prop should be about 1" behind the cutless bearing because when you move forward and backwards the engine moves back and forth about 1/4". Take a look at the shaft as it exits the stuffing box and this movement will be evident.

 

[Night Watch]

By saying cutlass bearing I believe you meant prop shaft coupler.
But in any case, the prop should be about 1" behind the cutlass bearing because when you move forward and backwards the engine moves back and forth about 1/4". Take a look at the shaft as it exits the stuffing box and this movement will be evident.

I've decided whether it's the cause of my initial problem or not I'm adding a Globe Drivesaver this week.
Probably the best way to get the standoff I should have put in before bolting the engine down.

 

[Ralph Johnstone]

The Catalina manual calls for a 0.003" tolerance when aligning prop shaft.

Catalina is telling you to try to get your angular misalignment between the prop shaft coupling flange and the transmission coupling flange down to 0.003" or less.

Is this why you're shooting for the 0.005" clearance between your prop and your cutlass ? This has no relation whatsoever to shaft alignment and as others have said, the usual clearance is 1" up to a max. multiplier of 1.5 times the diameter of your prop shaft.

No offence intended but I think it's time you reviewed exactly what shaft alignment means. This attached article is one of the best I have come across for shaft alignment. Your "first" alignment job is the longest and most painstaking but once you understand what's happening, several of the preliminary steps can be eliminated and the future alignments becomes quite simple. That is ............ until you hit a rock or worse with your prop.

 

[Night Watch]

I've read it!
I have my own personal copy.
My prop shaft is properly aligned.
I think I agree with others that I'm several millimeters too far forward and adding a little space between the prop and the cutlass bearing is the first thing I'm to do.

 

[Ward H]

I have a few basic questions because something does not look / sound right.
What year is your C30?
When was the aftermarket prop installed? Before or during you engine work?
What specs were used to match the prop to your boat and drive train?
Where did you get the picture in post #11? Did you post it to just show the prop? It's not a C30.

I'm guessing that you installed a prop from another boat and it's not sized for your boat and engine. I did a little research and found the standard prop for a C30 with atomic 4 was 12" 7 pitch 2 blade that maxes out at 2100 rpm. One poster on the Moyer forum posted he installed an Indigo 10/8 2 blade and his max RPM is now 2600.
Since you're seeing 3000 rpm, most likely the prop size and blade pitch is not sized properly and not biting the water, despite being a 3 blade.

I'd suggest you go over to the Moyer Marine forum and do some searching over there. If you know the specs of your Indigo prop ask them if it is suitable.

Ward

 

[Night Watch]

I have a few basic questions because something does not look / sound right.
What year is your C30?
When was the aftermarket prop installed? Before or during you engine work?
What specs were used to match the prop to your boat and drive train?
Where did you get the picture in post #11? Did you post it to just show the prop? It's not a C30.

Ward: I'm guessing that you installed a prop from another boat and it's not sized for your boat and engine. I did a little research and found the standard prop for a C30 with atomic 4 was 12" 7 pitch 2 blade that maxes out at 2100 rpm. One poster on the Moyer forum posted he installed an Indigo 10/8 2 blade and his max RPM is now 2600.
Since you're seeing 3000 rpm, most likely the prop size and blade pitch is not sized properly and not biting the water, despite being a 3 blade.

I'd suggest you go over to the Moyer Marine forum and do some searching over there. If you know the specs of your Indigo prop ask them if it is suitable.

Ward

Ward: Boat was built in 1979.
Prop was installed by the yard at Port Angeles Boat Haven by the previous owner 3 years ago.
The prop is matched to the engine, enough said on this point.
The picture from post #11 I grabbed from the Indigo website. It's NOT a picture of my boat just a sample picture of the "type" of prop I have.
I understand your comments about Moyer and their forum; I'm over there quite a bit. However, I've driven this boat with this prop more than 40 nautical miles under power last summer. Last summer I could get 3000 RPM and made better headway.
BTW: I've searched the Indigo prop comments on Moyer already. This summer when I haul out, I'll confirm the pitch and diameter of this prop which is what I should have done last summer, but I'm sure the previous owner would have purchased the correct prop for the boat. But I could be wrong. My atomic 4 engine and atomic 4's in general produce more HP than needed for a 30' boat. Plus, mine is bored 0.10 over.
One thing know one has mentioned is I could be getting cavitation due to a fouled prop and that's why I'm getting high RPMs.

 

[dlochner]

I agree. The prop shouldn’t really be up against the cutless. I’m used to seeing about 1” gap there. Having said that, if the engine is still getting to the right RPMs my guess for reduced thrust is still a fouled prop.

The rule of thumb is one shaft diameter between the strut and the prop.