Wiring 1979 Chrysler 100hp to Yamaha Tach?

[Frank Acampora]

That is a Hydro-Foil. The best known brand name is "Doel Fin." Some people swear by them , some swear at them. The opinions are like a88 holes. everyone has one.

It is basically used to get an underpowered boat on plane quicker. Some brands claim better fuel mileage. Some people think they are best thing since sliced bread.

My advice is this: It is only held on with four bolts. Try the boat and see performance with and without it. Then decide for yourself if you want to keep it on

 

[JoshJK]

Good enough. Thabks

 

[NYBo]

Yes, what Frank said. The skeg is the vertical "fin" at the bottom of the gearcase. Sorry for the confusion.

 

[JoshJK]

Ordered a 13 1/2 X 15pitch prop tonight from iboats.com. As long as it gets here on Friday I will be taking a few tools along to the lake with me this weekend so I can try the 15 and the 17 on the same day and report back the rpms for each prop. Wish me luck. I did get to ski behind the boat this last weekend with the 17 pitch prop. There was only one person in the boat and it took a little effort to get up. Hopefully the 15 prop will wake the boat up a little more and make it that much more fun, especially with a few more people in the boat.l

 

[MickLovin]

As far as the Hydrofoil is concerned, I had one on my 100hp 1979 Chrysler and it helped a little with hole shot. Personally I would be leaving your prop as a 17" unless you ski behind your boat then maybe the 15" but I left my 21" S/S on as I found it the best for overall speed, I tried the 17" S/S I had and lost about 3-4MPH.
With my 21" I had it at around 5k rpm at 43mph with the 17" around 5.5krpm at 39mph.

 

[MickLovin]

What size is your boat and what mph are you getting now, I had a 17" Carribean half cabin with the same motor on it achieving 44mph but that was one person only.

 

[JoshJK]

I have a 16' crestliner C160 fish/ski. Last week my speed was toping around 25-27 with two people in the boat. This was with an in dash speedo and the hull mounted speedo shown in the earlier posted picture. Hasn't been confirmed via GPS yet.

 

[JoshJK]

This is the actual boat

 

[MickLovin]

No Title

Sorry I don't understand how you aren't getting more from that motor, I would expect at least 35mph with your boat, what is your compression on it, mine was 150 - 155+psi on all cylinders.

 

[MickLovin]

Nice boat BTW

 

[JoshJK]

Using a very cheap auto parts store compression tester I got right at 120 on all cylinders. I believe the boat weighs right at 1080lbs from the catalog from that year. Then add about 25gl of fuel and a couple lbs for skis, ropes, misc gear and two mean that weigh appr. 160lbs each.

 

[JoshJK]

Speed is hard to verify right now sinc that is only read by the Yamaha speedo in the dash wish an add on sensor mounted to the hull. The speedometer line was hooked to the Yamaha outboard before but now that I had to put on this Chrysler I bought one of the sensor from a boat shop and added it to the hull to hook the vacuum line to.

 

[NYBo]

You are definitely way down on speed if your readings are anywhere close to right. I get 35-36 MPH with mine at 5K RPM, 17" prop.

 

[JoshJK]

I will have to tty to check speed via GPS on my phone this weekend

 

[JoshJK]

Yesterdays results from the lake were this 13 1/2X15 prop yielded a wot rpm of 3600 at 27 mph. Mph was with GPS. I do have a tach that I can hold on the end of the crankshaft and read actually rpm just to verify the tach mounted in the dash. Not sure why I would only be getting to 3600 rpm? This was done with only two people in the boat.

 

[NYBo]

The motor clearly isn't running right. Are you sure all cylinders are firing under load? Is the timing correct at WOT?

 

[NYBo]

Another thought: Are the carbs and throttle cable set up properly so you are really getting WOT?

 

[JoshJK]

I have checked the carbs with the engine off and the throttle blades are all the way open when the lever is pushed ahead. I don't know how to make sure that all cylinders are firing under load. also have not checked timing.

I didn't know which cable was for the direction gear shift and which was for the throttle when I installed this engine and control box. I pulled the button out on the control so that you could move the lever without shifting gears and that is how I set it up?

 

[JoshJK]

I watched Franks video on adjusting carbs and checking timing. What should timing be at WOT? My flywheel is marked to TDC and around 32 degrees. Still not sure how to check spark at WOT. I checked for spark on the wires a couple weeks ago, but was doing it by myself so I didn't get to see spark on the 3rd cylinder since I couldn't get the spark plug to lay where I could see it while cranking the engine.

 

[MickLovin]

The button is for neutral lock, you probably should have left it in. When you do the lever full throttle are your carbie butterflies horizontal.
I suspect your Tach maybe out, you can buy a cheap handheld which you can use to verify your Faria, that's what I did when I bought a digital tacho and had to set it up.
32 degrees is correct for this motor, you can go 30 but I went by my sticker, I believe you should get spark on #1 if you have it set at 32 degrees on the flywheel with it @ WOT, otherwise you don't have it set at 32deg. By adjusting the nut and screw assembly on the dizzy you should get it to 32deg. By turning the flywheel back and forth slightly with it set around 32deg. you should have spark at #1 at WOT. You can also have the flywheel set at the 32deg mark and be able to push the dizzy belt and produce a spark that way, the belt should only deflect 1/4" with a 0.08 feeler gauge. I have the 100hp manual if I can help.