New 4 blade Turning Point Prop...meh

[dsiekman]

No Title

 

[dsiekman]

I just sent Hydra Sports an email asking if they have any original build info on the specified outboard shaft length. Not holding my breath but I figured it was worth an email.

 

[ondarvr]

It looks correct, but a tape measure will tell you all you need to know.

 

[dingbat]

Your boat takes a 25" shaft.

Checking around, most running your boat claim mid 40's performance running 17" props.

I had a 1987 20' Grady Overnighter with a 175 Black Max on the back. Hydraulic trim tabs with 17", 3 blade stiletto prop. 5500 rpm @38-39 mph.

4800 rpm is way too slow for that motor.

What's the compression like

 

[dsiekman]

It looks correct, but a tape measure will tell you all you need to know.

Cav plate should align with keel, correct?

 

[dsiekman]

Your boat takes a 25" shaft.

Checking around, most running your boat claim mid 40's performance running 17" props.

I had a 1987 20' Grady Overnighter with a 175 Black Max on the back. Hydraulic trim tabs with 17", 3 blade stiletto prop. 5500 rpm @38-39 mph.

4800 rpm is way too slow for that motor.

What's the compression like

Thanks for the info! So are you suggesting I should have gone with a 17?

Don't know the current compression. That will be a project for the weekend.

 

[ondarvr]

Cav plate should align with keel, correct?

Well, sort of. There's no such thing as a cavitation plate, it's an anti ventilation plate, but people use the wrong term more often than the correct one.

It will normally be even with, or higher, and can be a few inches higher sometimes.

 

[jimmbo]

Cav plate should align with keel, correct?

It is trimmed in all the way in the pic, but if you trim the engine up until the AV plate is parallel to the keel, then you will get a better idea of how high/low it is mounted. It actually looks, as ondarvr said,"it looks correct". I guess your boat has a 25 inch transom.
If the engine checks out compression, timing and fuel wise, then I would have to say you have too much propeller, your engine needs 5300 - 5800 rpm, preferably close to 5800 @ WOT

 

[dsiekman]

Well, sort of. There's no such thing as a cavitation plate, it's an anti ventilation plate, but people use the wrong term more often than the correct one.

It will normally be even with, or higher, and can be a few inches higher sometimes.

Good to know, thanks

 

[dsiekman]

Tested compression today. Engine warm, throttle open. 100-110. Plugs looked good. Brown, insulator, no fouling.

I did notice a fuel leak I need to fix before running it again. While running I was getting a small spray between the carb and manifold. Other than the obvious safety and environmental concerns could that be part of the issue?

 

[dingbat]

Thanks for the info! So are you suggesting I should have gone with a 17?.

Possibly even to a 15p if running a 4 blade. I was running a 17p with a 3 blade.

Need to bring the motor up another 700-900 rpm