CPFITNESS

CPFITNESS

It had no problem starting and was idling pretty damn smooth to me but again, I'm a novice with this stuff. I am worried something happened to the cam, I know you are supposed to start it up and get her to 2000-2500 immediately for 20 minutes. They didn't do that right away, it was started and stopped several times and I admonished them for that and then we tried to do it on the hose but just not enough water flow and motor was getting hot. We finally took it to the ramp and dunked it but we got a good 20 minutes of run time then with seemingly no issues and then we were trying to sort out some other issues before we took it for another sea trial which is when this happened.

I'm stumped, can't help but feel like something gave way somewhere, I suppose it could be a vaccum leak on carb gasket as it seemed to have a slight idle hesitation when carb cleaner sprayer in one area but it was very slight. Very frustrated

Griff

Based on the valve covers, that appears to be 7.4 which is a 310hp version 454 with cast internals and peanut port heads.
The cam is a small upgrade and still smaller than 454mag cam. Nothing you are posting indicates that a lobe got wiped out.
Did the sea pump get new impeller/housing??

Why the heck would they do a JR Marine kit instead of just removing the transom assembly with the engine out??

CPFITNESS

motor was bought used. I had a different mechanic who ended up being a lying sheister install it. Didn't go through the motor or the outdrive at all like he was supposed to. By the time I figured it out he had literally packed up shop and run. Boat had a ton of other cosmetic work being done so I didn't try to use the boat after getting this motor put in. When I did finally go to try and use boat I had overheat on the dock and also discovered cracked gimbal ring. So I found this mechanic to do gimbal ring repair not knowing I had any major issues with motor. Gimbal repair was done with motor in boat and then motor blew up after.

I have tried looking everywhere for cam specs on Magnum and couldn't find them. Do you know what they are?

It's a brand new pump, impeller and housing. It's like the 4th impeller and housing because one of the many things uncovered through this process was bravoitis. Before we knew motor was bad, we kept getting hot under power. I researched bravoitis and so we installed a thru hull and strainer for cooling. Once motor blew and we took it out we confirmed bad bravoitis and we did the repair so we have excellent cooling flow through the lower unit and the thru hull. Also replaced upper and lower shift cable, throttle cable, inspected y pipe and changed that gasket. On the motor itself we also discovered a busted oil cooler so that was replaced. The only part not rebuilt or replaced on the motor is the power steering pump. We put on a new alternator and starter as well being proactive. Oh yeah, and when we bought the new seawater pump we bought a new mechanical fuel pump too.

I committed to fixing this boat right once I sold my center console last summer and realized that we may just keep and run this boat for another year or 2 until my daughter gets a little older and can more capably fish we will probably be doing more family cruising so I wanted everything like a new boat if I'm gonna be taking my family on it. Its frustrating because I should be a mechanics dream, I'm not complaining or haggling price one bit, just want it done right.

CPFITNESS

I found the mag cam specs and you are right, they are very similar so that's a bit of relief knowing it's not like I did some crazy insane upgrade. Crossing fingers that it's a random vaccum leak caused by who knows what and maybe a timing issue that will be easy to resolve. Will definitely have them check compression. Fuel has been in the boat for a year but was treated with seafoam when tank was filled. About half the tank has been run, I'll top off the tank with fresh rec90 next time out as well. With the higher compression from the domed pistons could lower octane fuel be contributing to this? Maybe top off with 93 to have octane end up at 90?

CPFITNESS

One last bit of info I forgot about. When we were idling back to the dock and temps cooked down some we noticed the thermostat housing was super cool as if the the tstat was stuck closed. They took the tstat out at the shop to test it and was functioning fine. A brand new circulation pump was also put on this boat after the rebuild and yes it was a marine circulation pump not a truck pump which I read can be problematic for some reason pertaining to the volume they pump or something of the sort

liberator221

When a engine overheats I like to replace the thermostat even if it wasn’t the cause. You just took it out of it’s normally operating range.
when an engine “diesels/runs on” they often times run backwards. This can blow off any vac lines or plugs, could also damage a gasket ( carb base /intake) Are you working on this or the mechanic?

CPFITNESS

Yes the dieseling a d runny backwards had me petrified of water going into the cylinders with this being a 454!!!! Hoping it's a carb gasket and not an intake gasket and hoping it was caused by the improper base timing. Those are 2 easy fixes. Mechanic is doing this but I'm trying to be an "educated consumer".

articfriends

iTrader: (1)

18 cc domes on pistons with peanut port 113 cc iron heads?? assuming zero deck clearance and heads resurfaced your at 10.2-1 compression with .050 duration of 218/224, hope your running 93, was carb rejetted and adjusted for new combination? you might have problems with running stock timing once its set "normal" if not runnning 93, dont forget, a motor will spark knock in a boat inaudibly over wind and exhaust noise, be careful as you go forward, Smitty

CPFITNESS

Thank you for this. Plan was to run at least rec 90 but not opposed to running 93 either, just trying to get through the rest of the tank of gas that is in it. I will definitely top off with 93 on Monday morning before we continue to mess with it. Carb was not rejetted but will look into it. Pretty sure it's a 750cfm and I was under the impression it would be fine as is. If anyone else cares to elaborate I'm all ears.