Timing, rpm, overheating on a mercruiser 260 chevy 350

[Buck Horn Deer Farm]

Back in the day, I could set the timing on a small block chevy by advancing until pre ign ping then back off a bit. Can you do the same to a marine engine? Does it need to be at 8' for best running?
I am at 8' now and I can only get 4300 RPM at WOT and best trim. The 4bl carb is wide open and the engine runs very warm, almost to the red. (I dont like to run WOT longer than it takes to get on plane). What should cruising rpm be with out using the secondary throttle?
This is a heavy boat, 1977 24' searay weekender. It had a 288 (chevy 305) but it had problems so I put in a good 350 with 30 more horses. I thought it would power this boat with less strain on the motor. I had the carb rebuilt. Could I have a prop size problem? It is a 16x16.
By the way, thanks for all your help in the past.

 

[John_S]

Re: Timing and rpm on a mercruiser 260 chevy 350

Re: Timing and rpm on a mercruiser 260 chevy 350

Well, there is a ton of questions in there! Check up in the stickys, there is a list of issues that can cause poor boat performance. I'll try to answer the timing. 8 degrees BTDC is the standard marine SBC 350 initial timing. What you need to check is the timing at wot. It should be in 30-34 degree range BTDC. If its not, check your advance weights and springs for rust, corroasion, etc. You don't want to go any further with the total advance, especially in a big heavy boat.

 

[Don S]

Re: Timing and rpm on a mercruiser 260 chevy 350

Re: Timing and rpm on a mercruiser 260 chevy 350

I would say the first thing you need to do is get the temperature problem fixed. You should never see over 170? (even at WOT) when running. Have you checked the impeller in the raw water pump? Did you have overheat problems prior to the engine change?
What outdrive do you have?

 

[Buck Horn Deer Farm]

Re: Timing and rpm on a mercruiser 260 chevy 350

Re: Timing and rpm on a mercruiser 260 chevy 350

It is a pre-alpha and I put a new pump kit in last year. I just took off the inlet hose from the lower unit water pump and cranked it over. Water came gushing out. I will check for a restriction in the manifolds or Y pipe. How do I check the shutters?

 

[Buck Horn Deer Farm]

Re: Timing, rpm, overheating on a mercruiser 260 chevy 350

I took the hoses off at the thernostat and ran the tap water hose through one while plugging the other two and it flowed through to the lower unit. Did the same to all hoses. While I had the engine running in a tub with fresh water running in to it I noticed that more water came out off the port side outlet and the starboard side had steam and some water. What might that be?