Welcome!

Does your motor have a plate on top that mentions typical WOT RPM? I'm not familiar with the 3.0 so I'm curious what it's supposed to achieve.

My 7.4's have a plate, circled below, with some interesting detail including expected WOT RPM.

 

Yes it does. It says 4200-4600. That's why I suspected I might be bumping up against the limiter, but I didn't think I was quite there. Also, the tach starts to jump around quite a bit above 4k, so it's hard (impossible) to tell what's really going on.

 

Yeah, the tachs are hard to trust. Mine are also all over the place.

Your top speed definitely looks a bit low (but I've never had a 170). I'd grab the size/pitch off your prop and see if there is a 170 specific thread here? I bet there are some owners here that can comment on top speed and which prop you should be running (if the one you have now is incorrect).

I'm curious - did the boat jump out of the water, get on plane super quick/easy?

 

First of all, thank you for the quick replies! I really appreciate it.

Yes, it seems to pull nicely right off the bottom. I played with the trim and was able to make improvements. In the end I trimmed up until it started to porpoise and then backed off a bit for best results. It just seems to start to run poorly (limiter?) and top out sooner than it should. I'll get the numbers of the prop later this morning.

Thanks again!

 

The prop number is kind of hard to read, but it looks like: 48 832830A45 19P. I suspect the 19P is the important number. Looks like that's the factory pitch for my model.

 

Thank you Pirate Lady. I learned a lot reading that post.

 

Check out the basic things , like timing. Check the cap and rotor ,and sparklers. See how all that looks. Just looking at the doesn't cost any money

 

Wasn't meaning anything derogatorily, only wanting to not confuse our new friend.

Twerth, were it me (new boat acquisition and all) beyond changing the oil and filters, I would start by confirming the timing is where it should be, throw some new plugs in it and hope for an improvement. If you are handy enough to do it yourself, I would additionally rebuild the carburetor if for no other reasons than current gas is crap, you don't know how long it sat, and to have a baseline on the calendar.

I believe the odds are with you if it had been cared for as it looks. Non use, time, and crap gas are not friendly parameters to an otherwise cared for boat.

 

Something else I generally do with a new acquisition is collect whatever documentation I can find.

If you go to Sear Ray's Website you may find Owners and Parts Manuals for your boat (or close).
Scroll down to RESOURCES near the bottom of this page:

Sea Ray Manuals

Here is the MerCrusier Service Manual for your engine:

 

I had already ordered plugs, fuel and oil filters and a carb kit. The carb doesn't look any too clean, and it felt like a fueling issue to me, so that's where I had intended to start as well. I had also pulled the plugs, and they looked good but they were gapped at .050". I believe spec is .035" so I reset that. I haven't tried to start it since then so the jury's out on whether that made a difference.

In the small bit of web surfing I've done to date, I've heard mention of a "special system" to set timing, but I haven't stumbled across any details. I don't see it in my owner's manual or the MerCruiser manual that came with the boat. I have a timing light and I know what the setting is supposed to be. Is it more complicated than turning the distributor?

 

The one I had was as simple as that, but it was likely ten years older than what you have, so I can't answer that question without referring to that same manual I just posted.
In any case, my bet is on the carb / fuel system.

You might drain the bowl just for shit and giggles and see if you get any water out of it. I had one years ago that would run fine as long you babied it, but trying to go balls out it would cough, spit, and sputter. Drain the bowl and it would fun fine for a couple months. That's when I learned to love ethanol; NOT !

Welcome to CSR! Good luck, sounds like you have everything well in hand.

 

Thanks for posting the service manual. It's A LOT more detailed than the little paperback brochure that came with the boat. And flipping through it, I may have stumbled onto something. In the troubleshooting section, one of the potential causes of bad high speed performance is an overfull crankcase. My oil appears to be ~1 quart overfull. I noticed that before I took it out last weekend, but I didn't have suction pump yet so I ran it as is. I'll be changing the oil probably tomorrow, and I'll measure how much I take out.

I won't be able to test that theory until next season, and I'll have messed around with several other things by then. The culprit might be hard to pin down but if she runs like she should I'll be happy.

Thanks again to everyone for helping me out!

 

For sure you don't want to run it that overfull. If you go through with your plan and accomplish all that before next spring, it will matter little what the direct cause was if it runs like it should. If it does not, you'll have a huge head start and the ability to diagnose the remainder.

Establishing a known baseline with time and hours markers is almost worth the effort all by itself.

Should have said earlier . . . Congratulations, that's a nice looking boat!

 

Where do you live

 

No rev limiter.

Check fuel quality - pump some out from the bottom of the tank by removing the fuel sender and put it into a clear jar.

Remove, inspect and clean the flame arrestor.

Let's eliminate some easy variables before you start buying too many parts. But a dirty carb is always on the list

 

Thanks LD. The guy I bought the boat from (short term PO, not the original owner) told me he had been running 87 octane fuel. In this area, that means ethanol. I ran it down to about 1/4 tank and then filled with 91 ethanol free and added marine stabilizer.

I got most of the way through winterization today. replaced the fuel filter, changed engine oil and filter, new spark plugs, drained water, filled with antifreeze and lubed everything inside the boat (I think). I cleaned the spark arrestor after I fogged, and it needed it. It wasn't plugged but fairly dirty.

Also, false alarm on the engine oil being overfull. I just hadn't wiped the dipstick when I checked it last time.

I'm going to be lazy here because I haven't done a search yet. I don't have a manual for the AlphaOne, so I wanted to know where/how to lube a few things. In particular, engine coupler/u-joint shaft splines (supposed to be a grease zirk?), tilt lock mechanism and gimbal bearing. Can I get to those things with the lower end installed?

Thanks

 

Even with it cutting out I would think 4000,rpm would be faster than 23mph. Should be in the 30 mph plus range, unless something is up with the prop, he's 7 to 800 rpm short that boat should do close to 40 mph

 

Yes, I agree. Definitley higher at 4K RPM's. Top end on this boat is mid to upper 30's. See what happens next year.

Coupler - keep bumping the engine over (flip the kill switch) till you see the zerk. Yes, space is tight.

Gimbal bearing - on the outside of the boat, on the stbd side of the piece that is actually attached to the boat (transom plate) there will be a zerk.

Tilt/lock - this is the easiest one There is no such thing on a stern drive - that's an O/B thing.

Pull the prop off and grease the shaft.

Did you use the antifreeze that has propylene glycol in it (and not ethyl alcohol)?

 

I can get to my coupler bearing. Gimble Is a sealed bearing so no grease there

 

Both kinds are pink - just mentioning that again, for clarification. But if you actually saw propylene on the label, good.

Yer welcome!

 

Yup. I checked the label. It's propylene.

 

The couple is a tight fit. I reach down though the access hatch and get it on the fitting. Then pump the gun

 

I'm an idiot. Still can't find a zirk for the coupler splines. Are you getting to this from inside the boat or outside? And where's the access hatch you mentioned? I'm not finding anything in the manual (or on Youtube) to point me in the right direction.

One more question (I promise). My trim gauge on the dash is a bit flakey. Trimmed all the way down, it reads zero (first hatch mark on the left). If it trim up, the gauge moves up but then drops back to zero. Does this sound like a bad position sensor or is it more likely the gauge?

 

No, not at all!

It's inside the boat - you won't have an access hatch - that's for a different boat than yours so that doesn't apply. You just have to keep bumping the engine till you see it.

99% it's the sender. You can try cleaning the connections on the gauge, but it sounds like the sender has a dead spot. They're constantly in water so they only last so long.

 

The coupler is on the back of engine, where the flywheel is. Zerk (B) fitting just stick out of the bell housing where the drive unit slides in (A).

 

I'm sorry it's inside the boat, straight down the back middle of the engine. The a few inches back towards the outdrive, like said above you may have to bump the engine. Bit pull the lanyard for the kill switch so it won't start

 

Thanks guys. I was in the right area but couldn't spot the zirk(s). I might have to do this by the brail method.

I have a remote start button so I can bump the motor with no danger of it starting. I had made several revolutions yesterday with a flashlight in the general area, but no success. I'll try again tonight.

 

It's between the back of the engine and the back of the boat in that section somewhere maybe a few up to 6 in behind the motor but it's definitely there or should be there