No power out of ideas

[Tahoe540]

Sorry long post
So I have a pretty stout 555 bbc. I had this engine in my 30 ft offshore boat and the motor pushed it to over 60mph in lake Tahoe (6200 elevation). When I sold it I kept the motor to put in my jet boat. I bought a new dart block because my old one had a crack. I used all the parts from the old block. I did use new rings with the new block and used the gap they suggested on the card. The motor sounds good idling on the hose. It is kinda hard to start at times. When I got it on the water it had no power when throttle is applied. It just won't pull and struggles to push the boat to the speed of the old stock 454. I have put a new carb, new distributor that didn't change anything. So I tore it back apart and I didn't see any issues. I have degreed the cam and it is half a degree off the cam card (LC is 113.5 instead of 114). I have the timing set at 10 initial and 24 comes in at 3000rpm.
I have it out of the boat again and cannot find anything wrong and all the valvetrain is good.

I am at a total loss

[superpursuit]

Is this boat running a heat exchanger for the engine cooling? If not, if the engine is fed directly from the cold water that you run in you may not have enough piston to bore clearance. With a heat exchanger you can run similar clearances as a car, but without it you need to increase the piston clearance. Cold block hot piston scenario. If you did not deliberately open up the clearance then this is most likely your problem especially as you say "it is kinda hard to start at times".

I hope this helps.
Allan.

[rustbucket79]

Driveline or jet bound up?
Impeller too course for the new engine?

[Tahoe540]

The pistons are Icon with the skirt coating. I will pull some pistons and recheck clearance. It does not have a heat exchanger. Only preheat is through the log exhaust so it is not lake temperature.

I checked the jet and nothing clogging it. I can turn the shaft by hand. I was hoping it would be that easy

[GARY C]

Cam icl seems very retarded from what I am use to? I am guessing it is a 114 lsa installed straight up?

Does it have a roller with a stamped steel cover? if so look at it to see if the cam is bulging it out under load, if the cam walks forward the power drops drastically.

[rustbucket79]

A dyno session might be the cheapest detective work you can do

[Tahoe540]

The pistons are Icon with the skirt coating. I will pull some pistons and recheck clearance. It does not have a heat exchanger. Only preheat is through the log exhaust so it is not lake temperature.

I checked the jet and nothing clogging it. I can turn the shaft by hand. I was hoping it would be that easy

[MadBill]

Did you check out the coil and ensure full voltage (13.5+) to it? I've rebuilt more than one carb trying to 'fix' a bad coil.

[JoePorting]

Why is the ignition timing so conservative? Shouldn't it be more like 22 degrees initial, 36 degrees total? Especially at 6200 feet. What's the compression? What's the cam size? I think your timing was just too retarded.

[Geoff2]

Higher elevation needs more timing.

[travis]

Log exhaust? That throws up a red flag to me...

[Dave Koehler]

I'm thinking based on the sluggish comment that bad coil, coil wire, etc are in play here.

[rebelrouser]

Not sure of your ignition system, but if it is triggered by a magnetic pickup type distributor, could you have reversed the polarity of the wiring when changing engines? With the polarity reversed the engine will still run just not well. I work on a few jet boats they run in the local rivers, and maybe just a coincidence but I had two boats act like yours and that was what it was both times. MSD has a technical bulletin about pickup coil polarity. Working at a GM dealership back in the 70's and we had a rash of cars with pickup coils wound the wrong polarity from the manufacturer. AS the bulletin mentions it is easy to verify with a timing light.

https://documents.holley.com/techlibrary_pickups.pdf

[mag2555]

So are you running the same Cam in this 555 cid motor as in the 454?

[Tahoe540]

I thought about the log exhaust as well but I have seen many blown engines with them. It lays over from the time you put a load on it. You would think it would start to lay over when you were getting more rpm? But yes it could be an issue.

I am running the same cam I have always had in the 555. I have switched no parts from the 454 except for the exhaust. The cam is a marine hydrualic roller with .632 lift

I have run 2 distributors with 3 different coils on 2 different caps. One coil was the stock one that came on my cheap proform hei. I then purchase a Davis Unified Ignition HEI and it did not change anything. I also had a spare DUI cap and coil that I used on both distributors.

I have tried as much as 16-20 initial. I thought it was too retarded too but hasn't had any kind of impact.

The elevation I run at with my jet boat is a lake around 4000 ft elevation.

I am going to make some changes to my fuel system. One thing I overlooked is the fuel water separator I have in line. I am going to bypass that and see if that makes a difference. I did not have this on my offshore boat.

I really appreciate the ideas on fixing this. There is some expertise on this forum.