Trojan Boat Forum

I have reciently purchased a 1977 F25 with 318 chrysler engine in it. It has electronic ignition. The boat has a velvet drive on it.

1) what is the top speed this boat should do
2) what size and pitch prop is the RIGHT prop for this boat.
3) What is the best ignition system for this motor
4) would trim tabs help this boat.

thanks for any help. i am at a loss. The boat doesnt seem to want to get above 10 knots. in addition, there is a definate hesitation to the engine when you go from idle to full exceleration. At this point i dont know the condtion of the bottom or if this is the original screw. Frankly if i had this boat new and it behaved like it does i would be wondering.

thanks in advance

dave

Tim tabs can help level the boat when cruising and they can also help in fuel consuption. By using the trim tabs you might be able to hear the engines run smoother. We did on one boat. We could trim the boat to where we actually save about 3 gallons per our and picked up about 2 knots.
We have them on our 11 meter Trojan and we haven't seen much change with them. We will have to do more running to be sure.

1) what is the top speed this boat should do ? I've heard numbers around 22-25 knots for F25's & 26's. I get my 1975 F26 with a 318 re-built this season up around 17.-18.5 knots at 3900-4,000 rpm depending on the number of people aboard, amount of fuel in the tank etc. [I run a little slower than many becasue I put an oversized rudder and a 6" keel extension on the boat to improve tracking stability.]
2) what size and pitch prop is the RIGHT prop for this boat? I'm running a 14 dia x 10 pitch with no cup on my F26. I had the prop reconditioned to class 1 tolerances. Some people say that cupping makes a big difference. I don't think thats your issue. Maybe some F25 owners will chime in on the right prop size.
3) What is the best ignition system for this motor? Check the chrysler disucssion board at http://www.marineengine.com/discus/ when they come back on line. They've been down for about a week as of 10/31/05, but should hopefully be back on-line soon.
4) would trim tabs help this boat? They probably will help, but not enough to gain you 5 to 10 knots.

There are a lot of factors that affect top speed. The simplest thing to check is the fuel filter/water separator. Check that first if you haven't already. You didn't mention what max RPM you are able to get from the engine under load. The 318 should max out around 3,800 - 4,000 rpm. Depending on the prop, load, etc. If you aren't getting close to that, then start by looking at the ignition timing. You should be able to see the spark advance about 20-25 degrees when you rev the throttle (to about 2500 rpm) with no load. If the spark timing isn't advancing, that will limit your power and prevent the RPM from going much over 2600 rpm under load. The springs on the centrifugal weights that control spark advance inside the distributor are prone to corrosion and can be replaced by an ignition shop.

There are many other contributors to lack of power if you can't get the RPM up. Low compression, carburetor issues, ignition problems. You will need to troubleshoot systematically. It took me most of the summer to get my rebuild running right, but eventually I got there. Good Luck!
Chuck

Well Chucka has provided you with good advice here. Perhaps I could just add a couple comments. I have a 25' Trojan Sea Raider "Grannyknot" with the 318 engine. My prop is a 14x11 cupped but I don't know just what prop your F25 would require. I easily jump up on the step and can attain 22kts. @ about 3000 rpm. and still have throttle left over depending on the load on board. I have never gone beyond 3000 rpm.as I normally run my boat at trawler speeds. --- Much slower. I use trim tabs and wouldn't be without them. I must agree with Chucka about the timing, and would suggest a general tune up and also take off your flame arrestor and clean it with solvent and blow it out carefully.

You mentioned that you feel a hesitation when going from idle to full throttle. Sounds like air or fuel starvation to me, clean that flame arrestor, and your fuel filters. that just might do the trick. Good luck. --- Ray

you dont know the condtion of the bottom ? bet a haul up and clean the bottom /runing gear will fix it
Paul