props

chietib · Post by **chietib** » Wed Jul 30, 2008 8:38 pm

:?: Hello everyone, I have recently aquired a 1974 Trojan F-32. The boat has Chrysler 225 horsepower 318's. Can anyone tell me what props should be on this boat? Friends have told me that this boat should run much faster than the 17 mph that it runs at wide open (around 3000rpms on the port engine and 3800 rpms on the starboard engine). I'm almost sure the props that are on the boat now are two different sizes because the rumor at the marina is that the guy that had it before me was rather frugal and put whatever was the best deal on the boat. Thanks for any info you can help me with.

prowlersfish · Post by **prowlersfish** » Wed Jul 30, 2008 10:01 pm

I'm sure one of the f32 owns will chine it . is the bottom clean ? and are the tachs correct ?

some of the F32 owners are running 16X16 but thats with chevy engines (more HP ) not sure if the gearing is the same .

jddens · Post by **jddens** » Thu Jul 31, 2008 12:13 am

3000 & 3800 WOT sounds alittle slow........not real familar with the cyrslers but WOT should be closer to 4000-4500 i think.....and that would give you more speed...................

Don Lumber · Post by **Don Lumber** » Thu Jul 31, 2008 6:24 am

Actually I was reading through some literature on my Mercruiser 233s and the WOT rpm was supposed to be between 3800 and 4200.

chietib · Post by **chietib** » Thu Jul 31, 2008 7:58 am

Thanks for the comments, The hull was very clean when the boat was put in the water in May but it was quite rough from many coats of paint.
I've noticed that if I back off the starboard engine the port engine will rev as high as 3700 rpms, but as the speed of the boat increases the rpms of this engine decreases. If the port engine rpms are increased the starboard engine rpms fall off dramatically. I did some web research last night and it seems like the boat should have 15 x 15's with a light cup. The gear ratio is 1.5 : 1 (from what I can tell). Does anyone know if this sounds reasonable? PS: I LOVE THIS BOAT!!!

g36 · Post by **g36** » Thu Jul 31, 2008 8:25 am

my f32 78 has the same chrysler engines and i am running 16X15 props. transmission 1.52:1, i can cruise easily 19.5-21 mph. at 3000rpm both engines. 3000 should not be wide open throttle.

randyp · Post by **randyp** » Thu Jul 31, 2008 10:19 am

Chrysler 318s should be 4000 - 4200 rpm at WOT, that is when max hp (225) is reached. They recommend no more than 80% of max rpm for top speed. My single can get the F-26 up to 25mph (GPS) when tuned up and half loaded with fuel and water with no others on the boat. That is within specs. You need to get those babies tuned up, at least take a look at new plugs and adjusting carbs. There is an engine manual available for sale at marinepartssource.com. I just got one and it's worth the price of a marina tune up!

chietib · Post by **chietib** » Thu Jul 31, 2008 10:55 am

Thanks again for the info. I will order a shop manual. I've recently installed new plugs, caps, rotors, plug wires, electronic ignition module (marine specific conversion type by petronix), coil, checked and lubricated the advance mechanism in the distributor, new voltage regulator etc., etc. for a seperate problem that I'm having. Maybe someone has an idea of what this could be. The symptom is simple. When the starboard engine is run for the first 20 minutes ( almost exactly every time) the rpms cannot be brought above 2000 without the engine coughing and backfiring through the carb. After the 20 minutes, the engine runs fine the rest of the day. I've changed all the fuel filters, water fuel seperator filters, fuel lines, checked the choke, installed fuel additives (lead substitute and sea-foam), reset the ignition timing (although not with an advance timimg light) and still the same condition. The only thing that seemed to help for a short time was the sea-foam additive. Any Ideas?

jav · Post by **jav** » Thu Jul 31, 2008 11:11 am

I have a 1974 F-32 that had chrysler 318's (1.5:1) gears when I got it. I researched props pretty heavily then and found the factory spec'd 16x16 super cup 3 blades when new.

The consensus was that these performed real well when the boat was new and very light. As folks added weight, and the painted bottom became less than ideal, the 16" pitch was just too much. Also, as the boats became heavier, the 16" diameter 3 blades are very boarderline as far as blade area goes, which puts the blades at or near cavitation levels.

When I repowered to diesels, I went to 17x14 prop scanned 3 blades and performance improved quite a bit despite having less horsepower - but this gets pricey. A good option if you can find a set, is 16" 4 blade props... very rare.

I still have a set of 16x15 3 blade props (no cup) that I used with the 318's and they produced a 17-18 knot cruise at about 3000 RPM and topped out around 23 knots at around 3600-3800 RPM. They were tuned (not prop scanned) and placed in boxes as spares... if your interested, I'd let em go cheap.

Lastly- you need to be sure your engines are healthy. Unless your props are really mismatched, both engines should turn the same RPM (give or take 100 RPM). On the 318's, you really need to check the ignition system very well. Distributer advance mechanisms, firing order, and points can all heavily impact performance. Check and then DOUBLE CHECK FIRING ORDER...this can get confusing on counter-rotating engines. Also- check fuel tenk vents as well as the pick up tube being absolutly clear. Make sure your choke mechanism is working smoothly and that the carburetor doesn't have a clogged fuel inlet screen.

Good Luck

randyp · Post by **randyp** » Thu Jul 31, 2008 11:48 am

And let's not forget my favorite (one that I am very familiar with). RUSTING INSIDE THE GALVANIZED TANKS. Check the fuel filter very closely for brownish deposits after a run. If the tanks are aluminum or plastic then never mind......

wowzer52 · Post by **wowzer52** » Fri Aug 01, 2008 9:02 pm

I have a 75 F-32 w/255hp, 351's, 15x15 lightly cupped props and run maxed out at 4200 rpm 28 knots.. A friend of mine has a 84 F-32 with chevy 350's, 15x15 props also. If Jav will part with his 16x15's no cup thats a good starting place. Pull the boat out and find out what you have or go diving. Sounds like you are headed in the right direction. also, look through the threads and you'll find a lot of conversation on this subject. Let us know what you come up with.

AuxiliaryComms · Post by **AuxiliaryComms** » Fri Aug 01, 2008 9:28 pm

I don't why it took me this long to make the link but my Sea Raider has the same engine, granted I've only got a single screw and my gear ratio be different but I could take a look at my prop and let you know what I've got.

Someone else here could tell us whether it'd be helpful, I'm new to this whole thing.

prowlersfish · Post by **prowlersfish** » Fri Aug 01, 2008 10:25 pm

You said when one eng slows down the other speeds up ? and the rpm decress as the boat speed incresses ?

Do you have a engine syncronzer ? if you do ,disconect it if its shorted it could causing these proplems (been there)

Any chance both engines are getting fuel from a single pick up ? one eng could starve the other .

when setting the time rember one engines timming marks should the oppset the other . if the marks are the same on bothe engines you could be setting the timming at ATDC instead of BTDC I have run into this on chrysler marine many times

you could have more then one proplem

chietib · Post by **chietib** » Sat Aug 02, 2008 12:33 pm

Thanks for all the great comments! I went diving ... not so bad if you can keep the guy on top from pluging the end on your snorkel hose ... on purpose! What I think I have is a 16 x 15 prop port side, and a 16 x 16 prop starboard side. No syncronizer but I should add that the engine rpm drop on the port engine is a new symptom. The port engine was running flawlessly until last weekend. The Chrysler timing marks are incorrect on the starboard engine but I found that prior to timing the engine on the starboard side. I set it 2.5* BTC. I pulled the plugs on the starboard engine and they are ALL black. The number 8 plug was so wet that I don't believe it had any chance of firing. I replaced them all again yesterday but I haven't taken the boat out again. I'm starting to believe the carb on the starboard engine is causing the backfiring. The choke opens right on que and the engine starts quickly (Rich?) I'm purchasing a carb kit and rebuilding it ASAP. I think it's running way too rich. Any thoughts? I contacted three different prop companies (new inquiries) that were recently recommended by friends and they've all come back with 15 x 15 with a light cup. Two other companies, both in Europe, came back with - 16â€ diameter x 3 blade 0.73 DAR High Thrust propellers, cast in Ni-Al-Bronze to class 1(I have no clue what that means) and - 16 x 16 3 blade propellers with a super cup.

I'm leaning towards the 15 x 15 with a light cup. These seem to make the most sense considering the comments about the boat gaining weight over the years.

Thanks again for all the help.

wowzer52 · Post by **wowzer52** » Sat Aug 02, 2008 1:42 pm

Sounds like you are getting it nailed down, good job. Keep us posted.