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Author Topic:   15x21 on 60 Bigfoot
Jim Ray posted 03-31-2004 06:53 PM ET (US)   Profile for Jim Ray   Send Email to Jim Ray  

I was not going to ask this question, but this thread sort of begs me too.

I just got my 2004 170 back from the dealer last night.

As delivered, it had a sticker on the engine that stated "Special Prop Installed". Engine is a 60 EFI BigFoot.

I have not owned a boat since I was 16, and that has been a while. I did not question the sticker, nor did I take much note of the prop installed.

Took it out for the first time, and it was almost impossible to get it in or out of gear. Once in fwd, the WOT was 3400 RPM, and it took it forever to plane.

After running it around for a little bit, we put it back on the trailer. Looking at the prop, it was marked 15x21.

Dealer took the prop off, and installed a 12 pitch prop, which I have not measured for diameter, but it seems to fill the space well. Comes close to the plate above the prop. Dealer stated that the boat ran well with the new prop, but weather keeps me from testing it myself. Still a little cold here.

Do any of you experienced BW owners have any info, or a theory as to why this prop would have been installed on a 170? And why on a 60 hp BigFoot? My faith in BW has been shaken. The sticker stating "Special Prop Installed" seems to indicate that it was deliberate. The dealer had no theory, but was not too thrilled with the choice, and had no ideas.


Jim Ray

Jim Ray posted 03-31-2004 06:55 PM ET (US)     Profile for Jim Ray  Send Email to Jim Ray     
Sorry guys, I thought I had hit Reply, not new thread. I will pay attention in the future.
Jim Ray
Jim Ray posted 03-31-2004 06:59 PM ET (US)     Profile for Jim Ray  Send Email to Jim Ray     
And in the wrong thread. Sorry again JimH. How can anyone this old be such a newbie?
Jim Ray
Moe posted 03-31-2004 09:42 PM ET (US)     Profile for Moe  Send Email to Moe     
I'm not sure what thread you were trying to respond to, so I'll respond here.

I have a 13-7/8" X 15" Black Max prop on the 60HP BigFoot EFI 4-stroke on my 150. I measured from the end of the prop blade to the anti-ventilation plate and got 5/8".

If you did have a 15" diameter prop on there, it was only clearing the AV plate by 1/16"... danged close.

For a 170 Montauk, a 60HP BigFoot should use a Mercury 14" X 13" pitch Black Max prop, part number 48-77340A33, "Used only with 40-50-60 HP BigFoot FourStroke, equipped with soft rubber hub for low horsepower, painted silver"

The problem with shifting like rigging problems.


Sal DiMercurio posted 03-31-2004 10:45 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
I'd say that was a major blunder on someones part.
I question as to why you only put a 60 hp on that boat ?
I feel a 60 hp is the absolute minimum for that boat, & when you put the minimum hp on a boat, you get zero performance out of it.
A 60 hp belongs on a 15 sport, not a 170 that weighs about double the 15.
That boat needs a 90 hp or better.
There's absolutly no way a 60 hp can swing a 15 x 21 prop on that boat & the dealer should have known that before they even thought about mounting it.
When ever you go backwards on a prop such as having to use a 13.50 x 12....[ pitch is less than the diameter ] you know your engine is no where near big enough for the boat.
I'm sorry to be so forward, but it really makes me shake my head in disgust when people think their saving anything by under powering their boat.
Your going to have to run that engine at or very near full throttle to even resemble anything near the lowest end of performance.
If I were you, I'd bring the boat right back to the dealer & give him a piece of my mind, then I'd have a 90 hp or whatever the maximum rating is for that boat.
When you go with the maximum hp ratinmg, you have the best of both worlds, such as great fuel economy, not having to run the hell out of it because 2/3 throttle will be just fine & your resale value will be right at the top, instead of a potential buyer saying, ...Gee, I really love the boat "BUT" it's way under powered.
Again, I'm sorry , but you made a big mistake in your choice of engines.
Sal DiMercurio posted 03-31-2004 11:35 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
I'm probably going to catch hell for the above post, but that dealer should have told you that the 60 hp will "NOT" do that boat any justic in the least way, & they absolutly should have told you which engine would give the best all around performance.
Sometimes I think they just don't care & as long as they sell a rig & get the money, thats the main thing & they care less if your happy or not.
I'm not upset with you, it's the dealers place to inform their customers of the best performance & fuel economy & the draw backs of an under powered boat.
I would certainly think they should have known a 15 x 21 prop is totally out of line on that rig, & if they didn't, they need to go back to school.
Moe posted 03-31-2004 11:52 PM ET (US)     Profile for Moe  Send Email to Moe     
Jim, the sky isn't falling.

Look at the Whaler performance results of a 60HP BigFoot pushing a 170:

versus a 150 Sport:

I don't call that "zero performance," but some might.

Yeah, I agree a 60HP isn't great for a 1450 lb 170 Montuak, but if all you want out of the boat is 20 knots (23 mph) through the chop, you're going to get that at 4,500 rpm (75% of max rpm) with the 60HP and a 14X13" prop, and the motor WON'T be overworked doing it, with 2.33:1 gearing and a 13" pitch, at about 2/3 throttle at the most. However, that is about the maximum you should run a motor for long periods.

Had you gotten the 90HP, you could've had 24 knots (27.6 mph) at 75% rpm and about 2/3 throttle... look at the Whaler performance graphs and get the info for yourself.


Sal DiMercurio posted 04-01-2004 12:24 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Moe, I can't find the specs for his engine, if possible, can you post them.
My gripe is with the dealer, not Jim Ray.
When a person spends probably $22,000 - $25,000 for a rig, you would think they could at least tell them the draw backs of minimumal power.
I'd like to think there's still time for him to go with the bigger engine, but thats his choice.
If Jim puts any type of load in that boat, he will understand why I'm stressing a bigger engine.
Sal DiMercurio posted 04-01-2004 12:32 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Moe, I got it to come up, thanks anyhow.
I doubt his boat will even plane at 3500 rpms, it's only 15 mph.
Moe posted 04-01-2004 08:49 AM ET (US)     Profile for Moe  Send Email to Moe     
Sal, I don't disagree that the boat's underpowered for most folks, and if the dealer hasn't applied for a title on the motor for Jim, he might consider swapping it out.

It'll probably plane at about 15 knots at 3700-3800 rpm with that 13" prop.

From what I've seen of this four-stroke motor, added weight doesn't seem to affect its performance much. That being said, it's probably a two-person setup by the time they bring along some gear. That may be all Jim needs.


LHG posted 04-01-2004 12:30 PM ET (US)     Profile for LHG    
Any 170 Montauk I would like to own would have a PAIR of 60's on it, on a nice little Armstrong setback bracket!
Sal DiMercurio posted 04-01-2004 03:59 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
The data sheet for Whaler says 15 mph, not 15 knots at 3800 rpms.
Any boat that must turn 3800 rpms to go 15 mph is a very, very sad setup.
Now put a couple of friends in the boat & he's lucky if it will even get on plane.
I'm certainly not trying to belittle Jim Ray, I'm hoping he will make the right decision & get a bigger engine before it's to late.
Even if he just wants to put put around, it will come back & bite him on the butt.
Remember, just because you put a bigger engine on the boat, dosen't mean you must use all it's hp.
The 90 hp will get far better fuel economy than that 60 hp working as hard as it's going to have to.
Moe posted 04-01-2004 04:14 PM ET (US)     Profile for Moe  Send Email to Moe     
Look again, Sal. It says:

3500 RPM 15.3 mph 13.3 knots
4000 RPM 19.3 mph 16.8 knots

Interpolating between 13.3 and 16.8 knots for 15 knots:

16.8-13.3=3.5 knot difference
15.0-13.3=1.7 knot difference

1.7/3.5 X 500 rpm difference = 243 rpm
difference between 13.3 and 15 knots

3500 RPM at 13.3 knots + 243 RPM = 3743 RPM at 15 knots

That's why I said between 3700-3800 for 15 knots

It runs just under 3500 rpm at 15 mph.


Salmon Tub posted 04-02-2004 05:41 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
Looking at that chart, the numbers look a little funny. For the opti to get 40 mph max with a 19" pitch is odd.

Also, despite the fact that the 60 has a lower gear ration, and a smaller pitch prop, at 600 rpm it gets a higher troll speed than the 90, what gives?

Moe posted 04-02-2004 08:55 PM ET (US)     Profile for Moe  Send Email to Moe     
Astute observation, my friend! It shows in the slip numbers:

We can probably write off the 60HP idle speed to a typo, but the whole range of 90 Opti slip numbers look wrong. Perhaps that was really a 17" pitch prop they were using. The slip numbers look more reasonable with that:


Sal DiMercurio posted 04-03-2004 10:07 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Moe, are you saying the 60 hp stats are acceptable ?
I guess we all have opinions & mine is, any time you must run an engine to 3743 rpms to get 15 knts, some one screwed up.
Now put 2 people & a full tank of fuel in that boat & it will have to turn close to 4500 rpms to get 20 - 22 mph.
I really don't see how you can condon this application.
Moe posted 04-03-2004 01:48 PM ET (US)     Profile for Moe  Send Email to Moe     
Sal, If you look at the tests on the Whaler site, you'd see they were conducted with 375 lbs of people and 2 full cans of gas (where the two 90s were tested with only 1 full can). So you don't have to say, "Now add..." They already did add.

We obviously see things differently, but then I've been overseas where they've gotten by just fine for many years with smaller displacment, lower horsepower engines running at higher rpms through lower (higher numerically) gearing than we do in the US.

Sal, no offense intended, but the difference between us is that with you, if one of your ideals isn't met, the sky is falling and disaster looms imminent. You're prone to exaggerations such as, "Now put a couple of friends in the boat & he's lucky if it will even get on plane." Hogwash! It'll plane just fine with 3 people.

Planing is a function of boat speed and weight. In fact, if you look at all the mph/rpm curves on any of the Whaler-posted graphs, you'll see a much shallower line through the transition region, where lighter motors allow the boat to plane easier because they don't get as bow-high/stern-low to the water as boats with higher stern weight from heavier motors, which actually require more horsepower to get through the transition region.

For me, if something isn't ideal (and I agree this setup isn't)... well, it just isn't ideal, but that doesn't mean it isn't workable. Obviously, Whaler thinks this setup, and the 115 4S on the 190 which performs _very_ similarly, is workable for some people, or they wouldn't sell it.

In this case, it means Jim Ray cruises a little slower, or runs a little more rpm at cruise, or compromises and does some of both.

If Jim's dealer is on the ball, he got the title applications for the boat and motor in the mail within a day or two of the sale, and the motor instantly became a used, rather than new one. There's no need to make him feel bad about his boat.

LHG posted 04-03-2004 02:53 PM ET (US)     Profile for LHG    
Looking at those performance graphs, the 90 2-stroke is missing. What they probably don't want you to know, probably means you should buy it, for less money too.

Also shattered is the myth that most conventional four strokes are quiet running at speed. Verados excepted, of course.

Bigshot posted 04-05-2004 03:00 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
They screwed something up. Aint o way ANY outboard is gonna hit 108 120 you can go deaf.

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