Engine Speed on 22 Cruiser

Grazer · Posted: Mon Jun 17, 2013 10:43 am Post subject: Engine Speed on 22 Cruiser

Hello All,
I had my new to me boat out this weekend and had a fabulous time.
I was wondering if my boat is operating as other boats with a Honda 90. My best cruising performance with a 22 cruiser, 30 gallons of fuel, kicker, camping gear/food, fishing stuff etc. was at 5000 RPM about 22 knots. While I could get more speed out of her, the fuel consumption (higher RPM's) would have been increased.
Also, I noticed my tachometer jumping around once in a while without noticing a higher revving sound. Could this be caused by prop spinning out of the water when the motor is trimmed up?

Thanks,
Grazer

Sunbeam · Posted: Mon Jun 17, 2013 12:46 pm Post subject:

Pardon me if this is totally known to you, but.... the motor will have a recommended WOT (wide-open throttle) RPM range. No matter what speed one plans to cruise at, one should prop the boat so as to achieve that recommended WOT RPM with the typical expected load in the typical elevation (sea level, etc.). Then everything else falls into place around that. This keeps the engine from lugging and etc. If you are on a river with current you can do an "out and back" run and average the two.

I don't have a Honda 90 (and haven't looked up a manual for one), but 5,000 RPM at WOT sounds low to me. Or at least at the very low end of recommended. I would think you would want to prop for closer to 5,500-6,000, but does the manual list a recommended range? For comparison, my Yamaha 80 recommends 5,000-6,000 RPM for WOT. With the original prop I was near the middle of that range; haven't tested my slightly different replacement yet.

Sunbeam

srbaum · Posted: Mon Jun 17, 2013 1:11 pm Post subject: Honda Info

Filling in the info that SUNBEAM stated regarding the manufacturers rated wide open throttle (WOT) RPM. The 75 & the 90 HP Honda for your engine's year is 5000 - 6000 RPM. The bottom line is that if your boat is loaded, your engine must be able to hit a minimum of 5000 RPM and if not, the engine would be considered overloaded (you would need to change prop pitch to achieve this minimum (more pitch gets you less RPM and less pitch gets you more RPM)).
This does not mean that any of us ever runs our boats at WOT, but it is the means of ensuring the RPM/load is balance for the engine design, regardless of the speed that you find comfortable. I rarely ever run above 14 kts...

Chuckpacific · Posted: Tue Jun 18, 2013 1:32 am Post subject:

The 'sweet spot' for me ( two 40s) was 4500 RPM.

Grazer · Posted: Tue Jun 18, 2013 2:23 am Post subject:

I appreciate the info, and I am aware of the 5-6000 RPM range for WOT on my motor. However, my question remains, is this speed of 22 knots with a Honda 90, somewhat loaded boat trimmed properly at approximately 5000 RPM's one would expect to achieve? I assume this is a ballpark value. My hope is that others with a similar setup could provide similar findings and validate my readings.

chucko · Posted: Tue Jun 18, 2013 6:47 pm Post subject:

I have a 90 Honda efi and cruising at 4000 rpm with fac stock prop runs about 20 mph,wot is 5900 which is perfect,so it sounds about right to me.

Sunbeam · Posted: Wed Jun 19, 2013 12:59 am Post subject:

Sorry, I mis-read your question the first time around.

DuckDogTitus · Posted: Wed Jun 19, 2013 12:08 pm Post subject:

A Fishin C · Guest

mine is very similar with 2-3 people, 5000 rpm will get me about 22 knots.
I have a Yamaha 90. I don't get nearly the performance others claim or c-dory claims. No bottom paint. I run a 4600 at 17 knots for best cruising mileage. I use a 17 pitch prop and get the same spinning at high rpms.

DuckDogTitus · Posted: Wed Jun 19, 2013 10:22 pm Post subject:

Grazer · Posted: Thu Jun 20, 2013 1:45 am Post subject:

Thanks for the responses. It seems regardless of motor brand that they all share about the same values as I experienced. This provides me with a good baseline, thanks again.

thataway · Posted: Thu Jun 20, 2013 9:24 am Post subject:

Top speed with a 90 and light boat at WOT is gong to be close to 30 mph. Most of us with 80's cruise in the 4000 to 5000 RPM--a few in the mid to high 3000. Yours sounds fine with the load you describe. The boats are subject to weight, and trim both. You should experiment with the trim tabs and the engine trim to get the best speed at a throttle setting.

I do recommend trim tabs and a "fin"--favorite is the Permitrim--to get the bow down in chop and avoid pounding.

Wandering Sagebrush · Posted: Thu Jun 20, 2013 10:22 am Post subject:

Grazer, your boat sounds about right, but knowing prop pitch, carbs vs EFI, and elevation play into it as well. The tach jump is something that my boat does too. When I key the VHF, I get induction and a jump in RPM.

Casey · Posted: Sat Jun 29, 2013 6:22 pm Post subject: Farthest 'North CBGT?

Not to hijack the thread, but Grazer/Katmai/+ an unnamed C-Dory
may have just constituted the "farthest North CBGT!"

We're all in Haines, AK! Smile

Best,
Casey&Mary

T.R. Bauer · Posted: Sun Jun 30, 2013 1:05 pm Post subject: Re: Farthest 'North CBGT?