Finally pulled my head..top cylinder ate a ring

[scout-j-m]

I was able to take it for another spin yesterday evening. I verified that the carb butterfly was perfectly horizontal. I also set the timing dynamically to exactly 30 degrees. I tried all of the my tests mentioned above: totally disconnected the rectifier/regulator, disconnected the tiny tach from the plug wire, and swapped the black/yellow leads on the switchbox to the wiring harness kill switch wire. None of those made any difference in performance except I think the timing may gave given me a slight boost in rpms. I also tried pumping the primer ball (was still hard) and also squirting a little carb cleaner in the throat at WOT to make sure there wasn't any kind of fuel delivery problem, which there wasn't.

Performance-wise, this time I was able to hit 36mph and 4500 rpms at WOT. The boat seemed to get up and ride on plane better than the first trip, even at lower rpms. It still idle pretty well and ran nice and smooth at high rpms's. It does seem to occasionally have a miss or two while accelerating hard but I still haven't fine tuned the low speed idle mixture screw like I need to. I guess at this point I will try to get through the break-in and see if my wot rpms go up over that time before considering a re-prop.

BTW, anyone know the LU gear ratio of my motor? I'd like to know to use it in some prop calculations. I seem to remember it was somewhere around 1.7 to 1.8:1.

 

[pnwboat]

Good to hear that all went reasonably well. Clymer lists the gear ratio in the 70HP and 75HP motors as 1.64:1.

 

[scout-j-m]

I used a prop calculator to input my various rpms and corresponding speeds to get an estimate of prop slip. Came out to about 16% give or take. I don't know much about this so I don't know if that is a reasonable number or not.

Sunday afternoon I drained my onboard 18 gal tank and swished around some denatured alcohol and filled it up with ethanol-free 87 gas and oil (don't worry, still using 25:1 ratio). I installed a new fuel water separator filter just in case. Then yesterday I was able to go cruise around for a couple of hours. Same results as the last run...in the WOT bursts I would occasionally hit 4500 rpms but mostly stayed around 4300-400 and topped out around 34, sometimes 35 mph. Again though it ran pretty nice and smooth at WOT. I still noticed the misses I mentioned earlier although it seems they are also happening very sporadically even just under WOT.

Before even discussing things to check, I did notice that the flywheel and stator are getting very warm if not hot. I noticed it when I pulled the cover to run it to verify that the filter was staying full and make sure it wasn't starving for air. When I did so I touched the flywheel and compared it to the head, block, and exhaust cover which were warm whereas the flywheel and stator windings were to the point that much hotter and they would be almost unpleasant to touch. Also looked like some stuff was melting from around the windings. I ordered an IR thermometer so I can check this a little more accurately. I'm thinking about strapping on my old stator and using my timing light to verify rpms and see if it stays cooler or runs any better.

 

[scout-j-m]

Been a while so I thought I would provide an update on my motor. Currently I am at around 7 hours on the break in according to my tiny tack knockoff. The motor is still running well. I went ahead and replaced my 16P prop with a new Turning Point 14P (aluminum, 3 blade). It got me up to 4900-5000 rpms just like they predict - 200 rpm increase per inch of pitch decrease. WOT speed decreased to about 33.5 mph. I chose the turning Point brand because for a $25 fee, you can exchange a used but undamaged prop of theirs for another. I thought this was a good deal because it would allow me to drop pitch to get my rpms in the middle of the WOT range and then if I noticed any performance boost after the break in was over and I went back to 50:1 gas I could exchange it appropriately. I'm still unsure if it is reasonable to expect anything different performance-wise after the break in is complete. It still baffles me how I could run 40+ mph pre-rebuild with the old 16P prop, when I know I already had low and slightly uneven compression, yet could only top 35-36 mph with the exact same boat/gear post rebuild. I did always add a can of seafoam to my tanks when filling from near empty, and always used ethanol free gas which is only sold as midgrade or premium near the lake I fish. Through the break-in I have been using ethanol free but also go my gas at a local station and got 87 octane from there. I'm just hoping all of that idling I did in a tank to troubleshoot my ignition issues right after the rebuild didn't have any ill affects on the motor.

Anyways, hopefully I will get to 10 hours over the course of the next couple of weeks and can transition back to 50:1 gas and take some compression readings to post here.

 

[fisheymikey]

i had the same problem. it was the flywheel laminate was touchinf the trigger and crated the heat. i noticed the groves into the trigger.

removed the laminated that was touching sanded down the flywheel. and then right as rain.

here is my link hope this helps you..
http://forums.iboats.com/forum/engi...chrysler-outboards/10022468-flywheel-very-hot

 

[scout-j-m]

i had the same problem. it was the flywheel laminate was touchinf the trigger and crated the heat. i noticed the groves into the trigger.

removed the laminated that was touching sanded down the flywheel. and then right as rain.

here is my link hope this helps you..
http://forums.iboats.com/forum/engi...chrysler-outboards/10022468-flywheel-very-hot

Thanks Mikey. I think I was just being paranoid all along regarding the flywheel temperature. Before the rebuild, the charging side of my stator was shot so that probably had an impact on the heat transferred to the flywheel and kept it cooler. Now that I have a functioning charging system, it makes sense that it heats up a little more and I just wasn't expecting that. I bought the IR thermometer I mentioned but haven't had a chance to test it out though.

 

[Frank Acampora]

There is a lot of misinformation about hydro-foils. If they are not necessary, then they will do no good and possibly hinder performance. If they are necessary, they certainly will help performance.

With a very narrow transom and heavy weight at the stern, your hull may be sitting low in the water, even on plane, increasing wetted surface area and slowing it. The original hydrofoil MAY have been helping to lift the stern, allowing the hull to gain more speed.

Since you did record a higher speed with it, try installing it again and see what happens. If you don't gain anything or if the hull handles in a way you don't like you can always remove it. And, incidentally, with the hull riding higher there will be less load on the engine and RPM may increase.

Remember: Everyone on the forums has an opinion on hydro-foils, just like oil brands, ethanol gasoline etc. Most is purely anecdotal and not to be trusted. If the hull seems to need one the only step to take is to try it and see what happens.

As far as prop pitch, dropping pitch within a NARROW range can help increase engine RPM. However, dropping pitch will often result in a decrease in top speed. If the engine is capable of turning it, higher pitch is the only way to get more speed.Remember: Pitch is like rear end gears on a car. At 2.73 the car will cruise the highway at low engine RPM. 4.11 or higher ratio gears will improve acceleration, but cars with these ratios are often limited top speed unless the engine has been modified for racing with a higher RPM limit.

THUS: try the hydro-foil with your original prop and note the results. If you are completely against hydro-foils, try Smart Tabs.

 

[scout-j-m]

Thanks Frank. With the hydrofoil installed and the original prop, I didn't notice much of a difference. It may have helped get on plane a little better and possibly made me lose about 1 mph or so at WOT. It did feel like helped handle turns better but not enough to matter. Based on all of that, plus the fact it seemed to create some extra noise, I probably won't use it. I have not tried the new prop out with it removed yet though.

I do feel like the stern is "squatting" more than it should but then again, it may have rode this way prior to the rebuild and I just didn't notice it since I didn't have anything to compare it to. The boat is loaded and weight distributed just as it always has been so the only possibility there is if my foam has become waterlogged somehow...which is unlikely because I keep the boat covered.

I'll just remove the hydrofoil and continue the break-in with the new prop and go from there. At least as it stands now I am closer to the mid range of WOT rather than borderlining right at the bottom end.