Got a new boat, got a few concerns

The boat is a 220DA Searay (24' LOA). The engine is a 5.0L mercruiser with an alpha one gen 2. We took it out yesterday and I guess I feel like it took a while to plane. That said, I'm also trying to get used to the trim tabs. Our last boat was a 16' open bow, so there's a lot of adapting to do. I don't have any sort of GPS yet so I cant say for sure the speed, but the highest I could get the RPMs was about 4200. Before I bought the boat I did a lot of research, and it seems with a 5.7L the RPMs should hit around 4800 full throttle. I have the 5.0, maybe 4200 is normal?

Another thing, this 5.0 is not the original engine, but the alpha 1 is. If the original engine was a 5.7, are the gear ratios in the outdrive kosher with a 5.0? Wrong prop? I think maybe.

For now the only other issue is some sort of hot start issue. It will fire up quickly most of the time, but twice yesterday after we sat for say 30 minutes, it was just turning over for a good 20-30 seconds before it finally started firing a little and then fired up. I haven't looked into it yet, but I'm going to check the fuel lines and makes sure fuel is staying in the carb, and check the spark plugs.

Re: Got a new boat, got a few concerns

A 5.0 is not enough engine for that boat . . . So, you may have to change out the prop to get a better match to the engine. Check the compression on the engine first, just to eliminate any engine issues.

as for the starting, I would check the ignition system for loose wires, bad connections, etc. Have a multimeter with you, and when it does not want to start, check the voltage at the coil, etc.

Re: Got a new boat, got a few concerns

Compression is good, Ill check the ignition system today when I go to the boat.

If my source is correct the 5.0 came with 1.62 ratio, and the 5.7 with 1.47. How much of a factor is this and can I swap out the prop to compensate?

Re: Got a new boat, got a few concerns

Hot starts on a carbureted engine requires that you apply neutral throttle (open the throttle). I'm betting you are not doing that.

Re: Got a new boat, got a few concerns

Nope, I'm not doing that. 95% of the time it fires up without doing that. Are we talking open it like 10%?

Re: Got a new boat, got a few concerns

Bumperlt12 said:

Nope, I'm not doing that. 95% of the time it fires up without doing that. Are we talking open it like 10%?

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Try it and see what works best for you. It's a carb, and they can be a little different on every engine.

You also need to use the trim tabs, and the drive trim both to get best results.

Drive all the way down until the bow starts coming back down, then trim up to keep the bow at the proper angle. Again, it's trial and error until you learn what works best on your boat.

Re: Got a new boat, got a few concerns

Yea I'm still trying to figure the trim tabs out, they're a lot of work when people start moving around in the boat.

I'm reading a lot of conflicting information about gear ratios between 5.0 and 5.7. Some say its the same, some say its different. I'm going to the boat tomorrow and I'll take a close look at the prop and see if i can get some marking on it, as well as the out drive.

Here is a fact, the max RPM i could reach was 4200. Assuming the engine is operating properly, what do I need to do with the prop to get the RPMs up to where they are suppose to be?

Re: Got a new boat, got a few concerns

Even underpowered a little, the trim tabs should help you get up on plane quite a bit. Keep them down when you first "punch it" and only start to bring them up when you're on plane.

Re: Got a new boat, got a few concerns

What does your boats dry weight?

I have a 2700 lb dry weight boat with a 32 gallon fuel tank, I had a 5.0 with 1.62 alpha 1 ratio. had a 19p prop ran great for 5+ ppl or 21 3-4 and tube or skier. I changed it to a 5.7(beefed up) 355ci(.30over) regeared the alpha 1 to 1.47 and had great luck with 21p prop, but I was had high rpms so i went to a 23p prop and still have a little trouble if I have a load, but 1-3 people usually isnt to much of a prob. my best luck was with a 4 blade 21p prop, great out of the hole shot, and was able to stay on plain at lower rpms but lost top end speeds. also your starting issue may be in the fuel system, mech fuel pump? bleed off?

Re: Got a new boat, got a few concerns

If you're turning the same prop with the lesser hp/torque engine then lower rpm's would appear logical. Which leads to the next subject. It appears the engine could be tuned for a lower pitch prop. It is working harder to maintain the previous performance of the 5.7? You are feeding it more than it can burn. It could be overworked and flooding out???Is it fuel injected? If so, I would go with a lower pitched prop., if not, I would adjust the carb(s) and lean them out a bit.

Re: Got a new boat, got a few concerns

Ok, I took some pictures of the number on the outdrive and the numbers on the prop. Niether of which are easy to read.

Prop says something like 48 18...... Thats all I can make out



Outdrive says .....7759

Re: Got a new boat, got a few concerns

Bumperlt12 said:

Ok, I took some pictures of the number on the outdrive and the numbers on the prop. Niether of which are easy to read.

Prop says something like 48 18...... Thats all I can make out

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That looks like a 19 Pitch prop. Probably too much for the weight. I would try a 17p or even a 15P. The 5.0 is going to be working overtime for a 24' boat. The PO cheaped out by not putting a 5.7 back in the boat.

Re: Got a new boat, got a few concerns

What is the Mercruiser serial number of both your engine and your drive?

The 5.0L engines used both gear ratios, just depends on the boat.

Re: Got a new boat, got a few concerns

If you have the boat up on plane with the tabs retracted and the drive raised a bit that's where you will get the highest rpms. If its only 4200 you do want a lower pitch prop. I looked at the pic, it's absolutely a 19. I'd go down to a 15 pitch which ought to get your rpms up to 4500 or 4600.