Merc 5.7 help needed

[strombolichef]

1984 5.7
Today I installed new SEI Oudrive and went for a boat ride, heres what happened.
1. Rough starting, but have a rebuilt 4 bbl carb, gas is not great.
2. When it did start, would stall at idle, then be hard to start again.
3. When it was in neutral, the engine will rev up to normal rpms.
4. When it is in forward, it will go to about 1200 rpms and stay there at wot.
5. Water temp, cycling between 200 and 230
6. Oil temp cycling between 10 and 40.

Oh yes there is a knock in the engine and a bit of a miss.

Where should I start looking? I am new to the inboard engine game and learning the hard way.

Thanks for your information.

 

[Bondo]

Re: Merc 5.7 help needed

Ayuh,... The advice given to SteveOH fits your question Perfectly....

You'll find Manuals for your motor up in the Adults Only section,.... Have a Look...

 

[Don S]

Re: Merc 5.7 help needed

A rebuilt carb and bad gas is a waste of time. Especially if water in the gas.
When was the last tuneup?
When was the last time the raw water impeller was replaced?
What outdrive and engine model?
Is the boat ran in salt water? Manifold and riser condition?????
Is this a knock like a rod, or lifter rattle, pinging or?????
What ignition system do you have points? Thunderbolt?? Since you put on a SEI outdrive, I kind of assume you have a Mercruiser, but now that could be a false assumption.
Have you done a compression test?

 

[strombolichef]

Re: Merc 5.7 help needed

Mercruiser 1983 5.7 pre alpha (SEI06 1.5 ratio) with jackshaft.
Has not been tuned up.
The copmression is not tested
The raw water impeller is new the pump was leaking so i redid the gastkets and impleller.
I dont know what kind of ignition there is nor how to tell (but Im sure that will change quick).
Run in fresh water, the manifolds look like they are in great shape and have all new hoses etc. Feel normal when running.

Thanks

 

[Don S]

Re: Merc 5.7 help needed

Since you know the manifolds and risers are in good shape, do they get hot when the temp is at 200+, or do they stay cool? Could also be a thermostat.
Could also be your raw water pump housing. I've had customers with overheats that changed the impellers and put a warped melted housing back on. Of course it wouldn't cool
You need to download manual #3 for your engine. #4 for drive, trim and transom shield.
You probably have the Thunderbolt IV ignition. Easy to ID. Has 4 screws holding the cap on, no points under the cap.
Sounds like you are WAY behind on preventive maintenance. Fuel filter check for water is a MUST. Assuming you have a water seperating fuel filter.