WOT

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Away
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WOT

Post by Away » Wed Oct 09, 2019 7:52 pm

Been on this site a while. Have had my boat for 6 years, not a lot of use. In theory engine were rebuilt with about 10 hrs on them when we purchased. Engines are 318s Have never pushed the boat. WHAT should it be capable of running at. Took it out today and ran 3800 rpm for 2 minutes, never been above 3000 before. Did not try WOT. I am not mechanically included. Good a wood work. It looks pretty good, but need to have a better understanding of what is safe performance wise.
F32 Fly 1975

rickalan35
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Re: WOT

Post by rickalan35 » Thu Oct 10, 2019 6:37 am

Away!

Are you my twin? I'm 70, live in Ontario, am good with wood and like you I tend to never open up my throttles.

Don't know about you but I don't seem to suffer many mechanical failures nor run over things either and I think my slowpoke style is part of that :)

But I have had to run from a storm a couple of times and I do realize that these engines need to be run faster on occasion.

All this talk and I don't have an answer for you except to say that fast for me was 3000 rpm. It'll go faster but I didn't go there.

Others on here will be able to provide answers for the performance of your 318's.

Season's winding down. Your boat still in the water?

Rick
Trojan 1994 370 Express, 502 Bluewaters

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prowlersfish
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Re: WOT

Post by prowlersfish » Thu Oct 10, 2019 6:47 am

A wide open 4000 rpm is what you want . 3800 and not at WOT sounds good would be nice to know what it is at wot to make sure you not goinh a lot over . 3000 is a good cruise rpm . I am not sure what speeds you should get , seen a lot of different numbers from a lot of people .
TROJAN F36 Conv.
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Life is to short for a ugly boat :D
2009 TROJAN RENDEZVOUS
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Away
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Re: WOT

Post by Away » Thu Oct 10, 2019 9:05 am

Thanks guys. Is 3000 for a half hour safe. Everything sounds great through to range of 500 to 3000 with no hesitation, never past 3000 before all I can say is at 3800 it was loud.

Rick, I'm only 5'7" lol

Boat being pulled around Oct 15.
F32 Fly 1975

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Re: WOT

Post by WayWeGo » Thu Oct 10, 2019 11:43 am

You should be able to cruise at 3,000 rpm all day.
1975 F-36 Convertible
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Away
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Re: WOT

Post by Away » Thu Oct 10, 2019 2:57 pm

Think my issue stems from, I can drive my little 2 liter car down I75 all the way to Florida at 80 miles an hour for 22 hrs stopping only for gas, bathroom and food and the tach only reads 2100 rpm.
Never felt comfortable with such high RPMs on the boat, did not want to break things. Consensus seems to suggest built for it. Feel a little more comfortable now.

Thanks guys!
F32 Fly 1975

mikeandanne
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Re: WOT

Post by mikeandanne » Thu Oct 10, 2019 5:17 pm

Old engines do not like high loads and rpm as there are only so many cycles in a set of connecting rods. Regardless of rebuild , unless they put new connecting rods in there as part of the rebuild ( I seriously doubt that ), If you are happy to run your boat as you already are, don't push it, IMO , there is no need to get max rpm unless you got brand new engines. That is my two cents worth.

Your road car has a new style engine, and the load on it at 70mph is nothing like what a boat experiences even at 1500rpm. Consider your drive all the way down I 75 if it were up a steep hill all the way.
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Away
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Re: WOT

Post by Away » Thu Oct 10, 2019 5:30 pm

Ok. now I'm not so comfortable, get up on plane and leave it here. Works for me, basically where I was comfortable.

Thanks.
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prowlersfish
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Re: WOT

Post by prowlersfish » Thu Oct 10, 2019 6:58 pm

Seeing what she will do wide open , give you a idea of how your propped . if you can hit or get near 4000 , then you know your good and the engines have a easy life running at 3000 . And if your only getting say 3000 at wide open then you could be pushing the engines hard even at 2500-2800 .



You could turn 3800 and likely more , your engines should have no issues running 3000 as long as you want .
TROJAN F36 Conv.
6BTA Cummins diesels
Life is to short for a ugly boat :D
2009 TROJAN RENDEZVOUS
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Away
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Re: WOT

Post by Away » Thu Oct 10, 2019 7:09 pm

It really is concerning. The alternatives our expensive, inconvenient and scary if this is where you live for the summer. On the hard for a month or three.

Again thanks guys.
Last edited by Away on Thu Oct 10, 2019 7:11 pm, edited 2 times in total.
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captainmaniac
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Re: WOT

Post by captainmaniac » Thu Oct 10, 2019 7:09 pm

I have 360s instead of 318s, so don't know how similar a speed curve you will see. Posting this anyways just in case it helps.

This is what I get - speeds are averages at that RPM over the past 20 years I have owned the boat (yes, I keep a Log, call me old school). The + / - show the Max / Min speeds I have seen at that RPM. Obviously things vary based on load, wind direction and strength, and sea conditions. Engines are probably a bit more tired today than they were in 2000 but not a huge difference in performance.

1500RPM is a good speed for me for displacement cruising. Around 8 knots.

The next sweet spot is 2800-3200 RPM. The boat is well up on plane, leveled out (with assist from the trim tabs), and the secondaries on the carbs haven't opened up yet so a lot less thirsty for fuel. I can cruse in this range (conditions permitting of course), for hours. I have done Hamilton to Cobourg, following shoreline and not just straight line route, in this RPM range multiple times - 5 hours+.

I have pushed it to 4000 / 4100 RPM but no more than 3-4 times since owning the boat, and for no more than a couple of minutes, just to see what it would do. Usually if I am running over 3200 RPM, its a case of "I really don't want to miss this bridge lift or we have to deal with this slop for another half hour", or trying to out run a storm.

Where you see the more 'flat' spots in the chart are the least efficient speeds... for me 1600 - 2000 RPM I am just burning more fuel and putting more strain on things, not going any faster. The range between 1200 - 1400 also doesn't really do much for me.

To your point re the car engine only revving at 2100 RPM -- that's called GEARS. Whether automatic or manual, car transmissions have gears. Boat transmissions typically don't. Our old V8s can handle the strain - they are actually made out of cast iron, and not just aluminum and plastic :D :D

Speed Curve F32 with 360s.PNG
Speed Curve F32 with 360s.PNG (89.61 KiB) Viewed 1266 times
Last edited by captainmaniac on Thu Oct 10, 2019 7:55 pm, edited 1 time in total.

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Away
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Re: WOT

Post by Away » Thu Oct 10, 2019 7:20 pm

Are 360 equivalent to 340's or 383's.

Thanks for your reply.
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captainmaniac
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Re: WOT

Post by captainmaniac » Thu Oct 10, 2019 7:59 pm

Definitely not an expert, but think the 318 /340 / 360 are all 'short block' engines https://en.wikipedia.org/wiki/Chrysler_LA_engine while the 383 and above are 'long block' https://en.wikipedia.org/wiki/Chrysler_B_engine

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Re: WOT

Post by WayWeGo » Fri Oct 11, 2019 12:20 am

I think captainmainiac meant to say small block (318/340/360) and big block (383/400/440) engines...

My last boat was 25 years old and had a big block GM engine: we normally ran at 3,000 to 3,200 rpm and on rare occasions would run at 3,600 rpm for limited times. Redline was at 4,200-4,600 rpm, which we only did rarely to make sure we were propped correctly and the engine was running well.

Our F-36 has 440 big blocks and redline is at 4,000 rpm. We normally cruise at less than 1,500 rpm to conserve fuel and relax, but I have no worries running at 3,000-3,200 rpm for extended times (other than my wife's comments at the fuel dock).

We are really talking about some different scenarios:

1) Running at WOT briefly to determine if the boat is working correctly.
2) Cruising on plane at a speed comfortable for the engines.
3) Cruising at hull speed to conserve fuel and relax.

If you are cruising at hull speed all the time, I think you need to get on plane for some time just to let the engines run at the speed they are intended to. It lets them warm up completely and burn off any carbon that might accumulate from extended running at low rpms.
1975 F-36 Convertible
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Away
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Re: WOT

Post by Away » Fri Oct 11, 2019 2:38 am

And I am loaded with carbon due to excessive cruising at 1500. Looking at using Sea Foam in another post.

Sea Foam Any experience with this product for heavey carbon removal. Either added to the fuel supply or added to the crank case. Good, bad or better alternatives.
Last edited by Away on Fri Oct 11, 2019 7:09 am, edited 2 times in total.
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