Poor engine performance when cold

bigriver 74

New Member
Jul 10, 2015
5
NW Wisconsin
Boat Info
1998 Sea Ray 190 with 5.0 L engine that was replaced 2009 with rebuilt engine
Engines
5.0 L Mercruiser Alpha 1 engine
I have a 1998 sea ray 190 bowrlder with a 5.0L mercrusier engine rebuilt in 2009. Pulled it out of winter storage and launched it. New gas in tank and new water separator filter installed. Started right up. All pressures good. Reved the engine out of gear, ran well. Placed in gear and gave it full throttle. Could not get above 2500 rpm and engine sounded like it was not getting any fuel. Backed off on throttle and idled for about 10 minutes. Engine temp came up to 170. Gave it full throttle. Higher rpms this time, then some surging and finally reached higher rpm to place boat on plane. Ran boat for about 60 minutes...never missed a beat. WOT was 4200 rpm and 46 MPH. Slowed down to idle speed and gave it the gas. Came right up on plane and ran well.
The following day went through the same routine and had same results, no rpm or output until reaching 170 temp. Then a surging and then good performance. Question: what is going on. This has not been a problem until this year. Originally thought of water in gas that is why I changed the water separator filter. Any insight anyone can provide would be great.
Thanks,
 
Carb or fuel injected? Could be a sticky choke if it’s carbed, that eventually pops once it gets hot enough.
 
I'd suggest it's normal for a motor to be sluggish if you don't give it time to get up to operating temp??? Perhaps that's a silly suggestion. But I don't know many folks that would willingly rip WOT on a cold motor....
 
Carbureted motor......choke may need adjustment

Fuel injected motor......check the coolant temperature sensor values.
 
I'd suggest it's normal for a motor to be sluggish if you don't give it time to get up to operating temp??? Perhaps that's a silly suggestion. But I don't know many folks that would willingly rip WOT on a cold motor....
Always let motor idle for at least 5 min so not really cold so not ripping the throttle as you assume. Thanks I think...
 
Always let motor idle for at least 5 min so not really cold so not ripping the throttle as you assume. Thanks I think...

5 minutes isn't enough to achieve operating temp in most boats I've been around. You also stated you had to troll for 10 minutes to get it up to temp...."cold" and "operating temp" are worlds apart I think?

I'm not a mechanic. That's why I use words like "suggest" and "perhaps". Your mileage may vary. Best of luck.
 
Could be loose or dirty wire connection. EFI engines are sensitive to a steady supply of correct voltage and the ground path is equally important as well. Check your alternator output and load test the battery.

As mentioned check what your CTS is doing. This problem has nothing to do with the warm up time. The ECM is made to compensate fuel and timing for a cold and hot engine.
 
Could be loose or dirty wire connection. EFI engines are sensitive to a steady supply of correct voltage and the ground path is equally important as well. Check your alternator output and load test the battery.

As mentioned check what your CTS is doing. This problem has nothing to do with the warm up time. The ECM is made to compensate fuel and timing for a cold and hot engine.

Ok help me out here...what is CTS and ECM? Have an idea but if you could define for me that would be wonderful.
 
CTS = coolant temperature sensor. A 2 wire sensor on the thermostat housing.

ECM = engine (or electronic) control module. The metal thing bolted to the inboard side of the port exhaust riser with several wire harness connectors attached to it.
 

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