Mercruiser greatly overpropped, need advice

[alldodge]

BTW is your 19P a 3 or 4 blade prop?

 

[Steelguitarman]

BTW is your 19P a 3 or 4 blade prop?

3 blade aluminum

 

[alldodge]

Thanks, then you need to reduce pitch.
With compression gauge being accurate, there is some kind of liquid in the cylinders (gas, oil, water or carbon build up)

 

[Steelguitarman]

Thanks, then you need to reduce pitch.
With compression gauge being accurate, there is some kind of liquid in the cylinders (gas, oil, water or carbon build up)

Could very well be a mixture. I could smell gas when I opened a few holes, and the engine have ran with a stuck open thermostat before I got it. Plugs were dark from being rich. I couldn't get it past 125 running under a load untill I changed the thermostat. A few of the plugs had flacks of carbon that just popped off, probably is some carbon from running cold for so long. I've only put about 4 hrs on the engine

 

[Steelguitarman]

Hello, wanted to give an update for anyone following this and so the information is posted.

I ended up getting a 15 pitch black max to replace the current 19 pitch black max.

What happened? I ended up gaining 2 more mph at wot, and brought the rpm up to 4400 when calm. I had over half a tank of fuel and 2 people on board. Allitle lower rpm than I was hopping but well in the range. It started getting windy headed back, still reach 4200 easily and then creeper up to 4300. Not ideal I supposed, but much better.

I definetly have the wrong gears put in it. Some marinas told me I needed a whole new outdrive, lol. They scoffed at me when I ask about doing a loaner prop to try one out. I'm happy with the outcome, 15% slip at cruising speeds(3050rpm at 25mph). I'm sure my fuel compsumption will improve as well. From what research I've done, 37 mph at wot is quite good for a larger boat with a 5.0

Thanks everyone for the advice and suggestions
Jordan

 

[QBhoy]

Hello, wanted to give an update for anyone following this and so the information is posted.

I ended up getting a 15 pitch black max to replace the current 19 pitch black max.

What happened? I ended up gaining 2 more mph at wot, and brought the rpm up to 4400 when calm. I had over half a tank of fuel and 2 people on board. Allitle lower rpm than I was hopping but well in the range. It started getting windy headed back, still reach 4200 easily and then creeper up to 4300. Not ideal I supposed, but much better.

I definetly have the wrong gears put in it. Some marinas told me I needed a whole new outdrive, lol. They scoffed at me when I ask about doing a loaner prop to try one out. I'm happy with the outcome, 15% slip at cruising speeds(3050rpm at 25mph). I'm sure my fuel compsumption will improve as well. From what research I've done, 37 mph at wot is quite good for a larger boat with a 5.0

Thanks everyone for the advice and suggestions
Jordan

I’d say that sounds a great result for you, all things considered. Excellent. Was fairly confident this would be the cause of it all.

 

[velociraptorfarmer]

Hello, wanted to give an update for anyone following this and so the information is posted.

I ended up getting a 15 pitch black max to replace the current 19 pitch black max.

What happened? I ended up gaining 2 more mph at wot, and brought the rpm up to 4400 when calm. I had over half a tank of fuel and 2 people on board. Allitle lower rpm than I was hopping but well in the range. It started getting windy headed back, still reach 4200 easily and then creeper up to 4300. Not ideal I supposed, but much better.

I definetly have the wrong gears put in it. Some marinas told me I needed a whole new outdrive, lol. They scoffed at me when I ask about doing a loaner prop to try one out. I'm happy with the outcome, 15% slip at cruising speeds(3050rpm at 25mph). I'm sure my fuel compsumption will improve as well. From what research I've done, 37 mph at wot is quite good for a larger boat with a 5.0

Thanks everyone for the advice and suggestions
Jordan

Given the load you had on board and being smack dab in the middle, I'd say you're probably good to go.