Tomcat 255 With Honda 135's Prop Question

R

redbaronace

New member
I have been reading about props to gain a better understanding on how to choose the right ones. The boat currently has counter rotating engines with stainless props. The part I am struggling to grasp is that the replacement prop we can use is both a different size and pitch than whats on there now. Without fuel flow monitors aboard, it makes the fuel usage (MPG) difficult to determine.

With the current setup 3 x 14 1/2 x 15, the medium loaded Tomcat 255 is only able to achieve a top speed of around 36 mph at 6000-6100 RPM. I believe the owner did fishing offshore and wanted a boat with a lot of low end power. Our preference would be top end speed but ideally best fuel economy at cruising speeds (20-30MPH).

We have an option to get Stainless props that are 3 x 15 1/4 x 17 and wondered if this would be a better choice for what we are wanting. Also as a side note we will be adding additional weight and installing permatrims soon.

Can folks with the Tomcat 255 and Honda 135's or 150's list what their prop size is and what top speed you can obtain.

Also, can any body reasonably guess whether moving from a 3 x 14 1/2 x 15 to a 3 x 15 1/4 x 17 is likely to achieve for us.
 
I can only speak for a C-dory 25 with a 150, but as always, I've got an opinion.

First, I've used 3 pitches for Journey On: 3 blade 15 (aluminum), 4 blade 16" (stainless) and a plastic 4 blade 16 1/2.

Second, I've tried the WOT bit for the boat sorta empty and loaded for cruising.

Third, here are my conclusions. The 15" pitch allows the engine to reach 5500 rpm with all loads. Next the 16 1/2 was to much pitch for cruising. We now use the 16" pitch whatever way we're loaded. And my recommendation is to never use a plastic prop. Also, I don't think 1/4" of pitch will be noticeable.

Journey On has been up to 25 knts in San Diego Bay in smooth conditions, unloaded. I'm impressed by 32 knts (36 mph.) We cruise at 18 knts max in smooth water. As you load up Journey On, and I'll bet loaded is a couple of thousand lbs, ~ 1 ton, the top speed really decreases. So that might explain the 15" pitch for offshore. BTW loaded includes cruising stuff, food and more people. It adds up quickly for a 25" boat, one or two hulls.

Boris
 
I'll look to see what props are on my boat which also has twin 135's. That said, with twin 135's I've never obtained speeds much over 39mph (34kts) so I think you have the correct props already (as indicated by 6000-6100RPM at wide open throttle). Permatrims will likely knock a little off the top end (they did in my boat). Also, if you did your speed testing with full fuel tanks, expect to lose a couple kt's off of the top end (when compared to say 1/4 full of fuel).
 
I may be a bit confused--did you buy a 255? I was under the impression that you were selling a Tom Cat 24 just a couple of days ago. If so, congratulations.

Are you using 4 blade props? Cats do best with stern lifting and 4 blade props. Also cats do better with the motors reversed to what the normal convention is for twin engine boats. --that is the right turning prop on the port side, and the left turning prop on the port side.

The Boat Test.com boat with 150 Hondas, used 15 1/4 x 19 Solas Lexor 3-blade SS props and got top speed of 41.1 knots (47.3 MPH of course light and new boat). Some of the others with 150's used 15 1/4 x 15 and 15 1/4 x 17 SS props. This is not too far off what we found when the boat was light--high 40's. With the Suzuki prop diameter and pitch is much different because of the lower gear ratio of the Suzuki lower units. At the mid range speed the 135 and 150 should do about the same--at the higher end, is where you get the more HP--and that might make the difference in WOT speed. At 6200 you should be hitting the rev limiter, so you may be under propped for the load you have.

Check the running height. The antiventillation plate should be use at the surface when running (that is the entire Permitrim visible on top of the water. Trim is also critical for the Tom Cat to get the best speed and MPG.

One person who was selling his Tom Cat claimed to get nearly 3 mpg--(over 2.5). Even the Boat Test was 2.8 mpg only at 20.5 mph 17.8 knots, most of the other speeds was 2.1 with some decrease to 1.7 at top speed.
Most of use got about 2.2 mile per gallon as a top number with good conditions.
 
thataway":3jit5c03 said:
I may be a bit confused--did you buy a 255? I was under the impression that you were selling a Tom Cat 24 just a couple of days ago. If so, congratulations.

Are you using 4 blade props? Cats do best with stern lifting and 4 blade props. Also cats do better with the motors reversed to what the normal convention is for twin engine boats. --that is the right turning prop on the port side, and the left turning prop on the port side.

The Boat Test.com boat with 150 Hondas, used 15 1/4 x 19 Solas Lexor 3-blade SS props and got top speed of 41.1 knots (47.3 MPH of course light and new boat). Some of the others with 150's used 15 1/4 x 15 and 15 1/4 x 17 SS props. This is not too far off what we found when the boat was light--high 40's. With the Suzuki prop diameter and pitch is much different because of the lower gear ratio of the Suzuki lower units. At the mid range speed the 135 and 150 should do about the same--at the higher end, is where you get the more HP--and that might make the difference in WOT speed. At 6200 you should be hitting the rev limiter, so you may be under propped for the load you have.

Check the running height. The antiventillation plate should be use at the surface when running (that is the entire Permitrim visible on top of the water. Trim is also critical for the Tom Cat to get the best speed and MPG.

One person who was selling his Tom Cat claimed to get nearly 3 mpg--(over 2.5). Even the Boat Test was 2.8 mpg only at 20.5 mph 17.8 knots, most of the other speeds was 2.1 with some decrease to 1.7 at top speed.
Most of use got about 2.2 mile per gallon as a top number with good conditions.
Click to expand...
Bob - yes, he bought a TC 255 and that's why he's selling the TC24 that he recently bought and put some effort and $'s into.
 
thataway":2ca09x4w said:
Thanks Roger, I must have missed when he got the 255!
Click to expand...

We did not announce the purchase of the TC255 because we are transitioning toward it.

If the TC24 does not sell, we will keep it and the TC255 will go up for sale instead.

In the meantime, we are fixing the TC255 to our liking.
 
Save your 15p props for a 2 month Lake Powell cruise, where you will be both heavy and high (alt wise). Someday I'll get a pair.
I just changed out 3x 14.5 x17p aluminum props for 4 blade Solas 17p alum (only $114) and I'm very happy...more 'bite' around the dock, better throttle-only steering, suspect better stern lift (she's arse-heavy and prefers to squat), better reverse off the trailer, 61k+ RPM (rev limited) on my first run, didn't check speed...yesterday got 5800 RPM with slimey bottom and heavy boat in cruising mode (spare everything from clothes to sunglasses to anchors to spark plugs, water pumps and thermostats, but not spare galley sink like Bob).
As usual, agree with Bob, though I bet he meant the reverse of 'conventional' twin propping is the RH motor starboard..mine was rigged that way by Mobile East Marine. Also, forget the Permatrims if you want top speed...he didn't say so, but they will subtract not add to top end. As I gain experience with my boat, I find it's not worth the trouble to 'barely' plane...the RPM'S fall off with each turn, wind and/or wave, and the constant 'fiddling' with looking down at RPM/ throttle/engine trim subtracts from my situational awareness. Yes, the best cruise is at barely planing just like most (all?) planing boats, but at 23-27 MPH, my heavy, slime-encrusted, befuddled-crewed boat with bimini will cruise all day like it's on rails, powers through any wake without losing RPM, and gets more air cushion in the tunnel=crew comfort, all of which is the POINT of running a 255. The difference in gas cost per year is not significant in my case (we trailer the boat and are happy with 13-15 MPG going 60 MPH through any weather in our 2500HD diesel).
Anyway, try a 4 blade 17p cheapo alum prop...it can be your spare as you dial in a SS.
Happy Boating!
John
 
gulfcoast john":3djo7nab said:
Save your 15p props for a 2 month Lake Powell cruise, where you will be both heavy and high (alt wise). Someday I'll get a pair.
I just changed out 3x 14.5 x17p aluminum props for 4 blade Solas 17p alum (only $114) and I'm very happy...more 'bite' around the dock, better throttle-only steering, suspect better stern lift (she's arse-heavy and prefers to squat), better reverse off the trailer, 61k+ RPM (rev limited) on my first run, didn't check speed...yesterday got 5800 RPM with slimey bottom and heavy boat in cruising mode (spare everything from clothes to sunglasses to anchors to spark plugs, water pumps and thermostats, but not spare galley sink like Bob).
As usual, agree with Bob, though I bet he meant the reverse of 'conventional' twin propping is the RH motor starboard..mine was rigged that way by Mobile East Marine. Also, forget the Permatrims if you want top speed...he didn't say so, but they will subtract not add to top end. As I gain experience with my boat, I find it's not worth the trouble to 'barely' plane...the RPM'S fall off with each turn, wind and/or wave, and the constant 'fiddling' with looking down at RPM/ throttle/engine trim subtracts from my situational awareness. Yes, the best cruise is at barely planing just like most (all?) planing boats, but at 23-27 MPH, my heavy, slime-encrusted, befuddled-crewed boat with bimini will cruise all day like it's on rails, powers through any wake without losing RPM, and gets more air cushion in the tunnel=crew comfort, all of which is the POINT of running a 255. The difference in gas cost per year is not significant in my case (we trailer the boat and are happy with 13-15 MPG going 60 MPH through any weather in our 2500HD diesel).
Anyway, try a 4 blade 17p cheapo alum prop...it can be your spare as you dial in a SS.
Happy Boating!
John
Click to expand...

I can appreciate your advice for keeping the props for high altitude. Where we are, there is so much good opportunity for boating that there is very little desire to travel far with this heavy of a load. The furthest we would likely trailer the boat would be to the coast to have better opportunities for fishing (like rogerbum).

I am definitely open to Aluminum props, but do not want to throw money away trying to find the right size/pitch/blade combo. The 2 sets of props mentioned are already in our possession. Whichever one we do not keep, will get sold. My backups will be aluminum rather than a 2nd set of stainless props.

We also did order the permatrims and they are in a box waiting to be opened. The permatrims really did help our 24 and I figured that the 255 would benefit as well. The feeling I get with the 255 is that the rear seems really heavy. Im hoping that the permatrims will help balance the boat fore/aft and help the boat to ride level at slower speeds. Since we often travel with another boat (22 cruiser), we cannot always utilize the Tomcats speed. When the 22 needs to slow down to 14mph, we will probably also slow down to stay close. The other option is of course to race ahead and wait for them to catch up.

Can you let me know what aluminum prop you used? I know you said 4 blade alum 17p, but how about the diameter.
 
Sorry, RedB... I failed to post I am only getting 35-36 MPH WOT @ 5800 RPM with the 4 blade, 14.5" x 17p Solas props (Get the biggest diam that fits your gearcase).
Ensure your cavitation plate is skimming the surface in smooth water like Dr Bob said (for me this is the second lowest hole on my Yami's, different no doubt on your Honda's).
My 'digital' readout gauges are really analog, I suppose, since the engine harness is not using the Yamaha Command Link output. I plan on adding the engines to my Garmin N2K network in the off season, and I don't really trust analog outputs to be +/- the 200 RPM needed to really 'dial in' propping. Dr Bob may well dicker with me re this.
It has been reported many times before on this forum...do not trust the specs on your newly purchased props, take them to a pro and get a MRI scan ($50 each on my orig props, 1 blade was bent and all were closer to 16 than 17p). You should be able to get a MRI on your knee for $50 cash at any WalMart super store....but don't get me started!
Agree yet again with Dr Bob that we can't compare our gear ratio and therefore prop pitch rec'd to Suzuki's (including, apologies in advance for my errors, Top Cat, Thataway, ViewFinder, Destiny II, Napoleon, etc).
All that said, Dr. Bob is right that a 4 blade prop (15 to 17p, 19P+ for Suzi's) winds up in the best of all Tom Cat worlds.
As I zoom in, slowly, on our best options, I believe a 4 blade offshore SS PowerTech prop at a custom 16P with lots of cup will turn out perfect for my rig, but to each his/her own, and our best to You and Yours!

cheers,
John
 
John is absolutely correct--we lost a minimal amount on the top end with the Permatrims--but we did have a fair amount of gear on the boat. I did not notice much difference in the time to plane-(pretty fast with the Permatrims. My impression is that MPG was about the same with Permatrims.

The boat would plane at a lower speed, but there were some real negatives, with bow trimmed down at 10 knots--the was a lot of water coming up around the stern…It was not a speed I wanted to run at, with engines trimmed down.

We would run the boat all day at 22 to 30 knots and not much noticeable of difference in MPG. The boat runs great at 25.

I preferred the SS props, less flex--but there are pluses and minus to both metals. If you are gong to a higher pitch, I would be looking at the 4 blade 17" pitch like John has. Be sure that you are going to be running your boat with the load you have aboard now. If you are going with a higher load, I would stick with the 15" props. (Actually with with the Suzuki you can get in the 20 to 21" light boat. pitch because of the lower gearing in the lower unit.) Some prop suppliers will let you try a prop--definately a prop scan is always in order, but don't let John pull your leg about MRI!

A prop is not a constant pitch, the various parts of the prop will have different pitch from the hub to the tips. What the prop is stamped is basically the difference between the hub and the tips--inbetweeen it will vary--it is not usually a flat surface. The prop scan not only balances the prop, but makes sure that the prop is the correct pitch at the proper place. It also gives a record of the pitch, the rake and the cup.. It makes sure that both props are the same. I have most experience with prop scans with inboards, but they are useful for outboards, and making sure that you have the best prop, and most efficient for your boat.
 
We are running Honda Stainless 3 blade 17" pitch props on Discovery. WOT at Lake Powell ( 3600' elevation) is about 35MPH. We Have used these props everywhere from 9000' (Fishlake, UT) to sea level. Since we rarely run faster than 20 MPH we just use the same props everywhere we go. Mileage is usually in the 1.8 to 2.2 MPG range. We spend a lot of time trolling on one engine or slow cruising at 5 or 6 MPH. As long as the RPM's are under 2000 RPM we get 4 to 5 MPG. We have the Honda 135's on a TC255. We are usually moderate to heavy loaded for extended cruising.
 
I need to buy a pair of spare props for Discovery. I have Honda 135's and have been happy running Honda 3 blade, 15 1/4" diam. 17" pitch Stainless props. I am thinking of buying Solas 4 blade 14 1/2", 17" pitch spares for next summers SE Alaska trip.
 
Hi Brent/Dixie!
You didn't say, but I suspect you're looking for aluminum 4 blade props for your spares. I switched to those same SOLAS aluminum 4 blades (from IBoats.com) and really like them as my Primary props ...I'd never go back to a 3 blade for a 255 now... better reverse power off the trailer, better idle control, better/awsome 'throttle-only steering'.
Conventional Wisdom would predict a WOT 200 RPM or so loss when switching from SAME BRAND 3 blade to 4 blade. SOLAS claims to make some OEM props; no idea if Honda is one of them.
For $125 each or so, you can get two SOLAS 4-blade aluminum props for under the cost of filling up the gas tanks.
When (if?) you hit an Alaskan deadhead, it will not ruin your outdrive. I have not yet come over to the camp (despite Dr. Bob being a member) that SS is usually worth the extra cost/longevity and the 2 MPH or so added top speed. Yes, having huge polished stainless props looks good (and boys like me are attracted to shiny bright objects, like crows, but with less brain power).
You can have my old 14.5, 17P aluminum used but scanned/painted (un used since then) 3 blade props for 50% of whatever lowest new price you can find before I put them on Ebay. However, I really think you should try the SOLAS 4 blade...you'll never go back. In fact, I renege on that offer and insist you try the 4-blade SOLAS before even considering anything else. You'll be glad you did!
Cheers, and good luck experimenting!
John
 
Thanks, John

I think I will try the Solas Amita 4 blade 14.5 x 17" pitch props. $112.00 each at Boats.net

I think I will just put them on as the primary props for the Alaska trip and take the Honda 3 blade 15.25 x 17" SS props as the spares.

We anticipate a lot of hours use at under 2000 RPM and 6 to 8 knots. Just slow cruising and looking at the scenery and wildlife.
 
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