Prop type for my boat type?

[Scand]

Hi

Need some advice. Have had some problems with a boat motor, a Mercury V6 135 hp from -88, I found that the linkage to the carburetors were loose and not syncronized so the motor was not running at full trottle. Found a service manual, made some adjustments, and the motor suddenly gave a lot more power. Now the prop sizing may be an issue.

The boat is a small english speedboat, (Fletcher) hull weight about 750 lbs. Length 16 feet, beam 6 feet 2". Motor weight about 400 lbs. Equipment 100 lbs. V-hull. Gear box 2,0:1. I ran the boat at a varm humid late summer day with a 2 person crew. Propeller Solas Amita aluminum 14,5" diam, 21" pitch. WOT for the motor is 5000-5500. I had problems with the tacho, probably a loose contact, but it was certainly above 5100 rpm and perhaps above 5500 rpm. GPS-speed was 42 knots. Hull was dirty with osmosis blisters, so it was running with some resistance in the water. I will fix the hull during the winter.

I have 2 propellers which I can test, but the question is if these propeller types are OK for this boat type? What performance can I expect from this combination of boat and motor/prop?

1. Stainless 23 pitch Laser-2

2. Stainless 21 pitch Solas HR Titan


Thanks in advance/Hansen, Sweden

 

[achris]

Re: Prop type for my boat type?

Hello Hansen,

The first thing you need to do is get an accurate tacho on it. Only then will you know what the engine is truly doing.

As for propeller selection... What are you using the boat for? Different propellers have different characteristics, and the best for one job would not necessarily be the best for another... Are you skiing, cruising, looking for top speed?

Chris, Australia

 

[dan02gt]

Re: Prop type for my boat type?

Both of those props should work well for your boat. Like previously mentioned you'll need a working tach to make sure your in the correct WOT RPM range.

I suspect the 23P is what you want because if that 135 is running strong it should have no problems turning the 23P on that lite hull and get you into the mid 50s (MPH). Also, a jack plate would help you get everything dialed in.

 

[Scand]

Re: Prop type for my boat type?

Hello Hansen,

The first thing you need to do is get an accurate tacho on it. Only then will you know what the engine is truly doing.

As for propeller selection... What are you using the boat for? Different propellers have different characteristics, and the best for one job would not necessarily be the best for another... Are you skiing, cruising, looking for top speed?

Chris, Australia

Hi guys

Should have mentioned that the tacho seemed to be alright up to 5100, then the needle started to go crazy. At 5100 I glanced at the gps and if I remember correctly it was showing 38 knots.

The Solas alu prop is OK for skiing, it gives a good strong start. As for the new propeller choice I am looking for a speed propeller. The boat had a 19 pitch propeller from the beginning, this was probably a choice made from mainly skiing and also, perhaps, that the motor was not running 100%.

I was thinking that the Solas stainless 21 pitch might be a good multipurpose propeller for both speed and skiing and the Laser-2 might be a speed propeller........

Best regards/Hansen

 

[dan02gt]

Re: Prop type for my boat type?

Hi guys

Should have mentioned that the tacho seemed to be alright up to 5100, then the needle started to go crazy. At 5100 I glanced at the gps and if I remember correctly it was showing 38 knots.

The Solas alu prop is OK for skiing, it gives a good strong start. As for the new propeller choice I am looking for a speed propeller. The boat had a 19 pitch propeller from the beginning, this was probably a choice made from mainly skiing and also, perhaps, that the motor was not running 100%.

I was thinking that the Solas stainless 21 pitch might be a good multipurpose propeller for both speed and skiing and the Laser-2 might be a speed propeller........

Best regards/Hansen

I think your dead on with that. Run the 21 when she's loaded down and skiing and the 23 for speed.

 

[Scand]

Re: Prop type for my boat type?

Hi

Thanks for the feedback. I bought both a Laser2-23P (used) and the Solas HR Titan-21P (new), but right now it?s winterizing time in Sweden, so it?s for the next season. USD is low compared to swedish kronas right now, so it feels like it is sale on US products.

Best regards/Hansen