1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Another query: Like I said, everything seemed to run quite nicely. A few things I noticed:

1. Was able to plane out with a nice top speed, with a maximum RMP of about 3800. Does that seem a bit low for this motor?
2. Shifting into gear, a BIG CLUNK. Shifting into neutral, smooth...
3. Idle (neutral) rpm ran at about 1200, while my lowest RPM once in gear was 1000. Not sure if that matters. Also noticed that when shifting out of gear to neutral the motor almost stalls out.
4. Slowest speed in gear is too fast for trolling:grumpy:! Any way to adjust, or time for a trolling motor?

 

[bonzoscott]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

1. Look up your engine & RPMs here Boatinfo - The library, containing manuals, brochures and other technical documents from the last hundred years!
Both Idle and Max. I think idle should be 650-700. Verify max in link I provided, but I think 3800 is a bit low.
2. Your idle is too high and that's why you here a BIG CLUNK. A "clunk" is normal but not BIG.
3. Idle covered above. Not sure about almost stalls out when shifting to neutral. Maybe shift interrupter. Make sure you shift somewhat swiftly and don't drag slowly.
4. Again, find your motor in the link I provided - set timing and idle by procedure.
Good luck!
My first boat was a '74 Crestliner 15 footer. I still miss that thing!

 

[fishrdan]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

3800 WOT RPM is low, should be 4200-4600. What elevation are you boating at and what is the prop pitch?

Idle should be 650-700RPM, with a warmed up engine, idling in gear, while on the water, need to adjust the carb's idle speed and idle mixture screws (3), or possibly rebuild the carb if it can't be adjusted low enough.

Coming out of gear and the engine stalling a bit is normal, as long as the shift interrupt switch is not completely killing the engine.

How fast do you want to troll, 1MPH, 2-3MPH? I have a Troll-a-Matic plate on my 140HP and it slows the boat to a crawl, below 1mph. There are other options too, buckets, bags, trolling motor, kicker motor.

[edit, looks like bonzoscott beat me to it...]

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

3800 WOT RPM is low, should be 4200-4600. What elevation are you boating at and what is the prop pitch?

Idle should be 650-700RPM, with a warmed up engine, idling in gear, while on the water, need to adjust the carb's idle speed and idle mixture screws (3), or possibly rebuild the carb if it can't be adjusted low enough.

Coming out of gear and the engine stalling a bit is normal, as long as the shift interrupt switch is not completely killing the engine.

How fast do you want to troll, 1MPH, 2-3MPH? I have a Troll-a-Matic plate on my 140HP and it slows the boat to a crawl, below 1mph. There are other options too, buckets, bags, trolling motor, kicker motor.

[edit, looks like bonzoscott beat me to it...]

Elevation varies, but where I was at yesterday would be about 3800 feet. The previous owner lived at about 2800 ft, but I have no idea where he operated it. I haven't adjusted anything on the carb yet, so perhaps once I solve the not starting issue, I'll get this thing plugged into a snorkel and play with the carb a bit.

I'm new to the I/O world, not familiar with the Troll-a-matic. I'll check it out. That was the nice thing about my outboard... could set it just about to any speed! I did see a REALLY cool electric trolling motor setup made by Marinetech. I believe it was called the Navi-gator. Very cool. Expensive.

Oh, prop pitch is 19.

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

I have a Troll-a-Matic plate on my 140HP and it slows the boat to a crawl, below 1mph.

This?

Trol-A-Matic Trolling Plate

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Fixed the not starting issue! So incredibly simple... loose screw connection on my ignition switch.:stupid:

Also, adjusted the idle and got it down to around 700-800. I can get it lower... but I swear it will stall out if I do. As it is the motor seems to idle a bit rougher. BUT - WOT appears now to be around 4600. I almost wonder if it just runs lower in the water??? Or... perhaps my prop pitch is a bit off.

Thoughts?

 

[fishrdan]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Elevation varies, but where I was at yesterday would be about 3800 feet. The previous owner lived at about 2800 ft

Oh, prop pitch is 19.

If the PO is available, I'd ask him where he boated/fished, to find the lake elevations. I boat anywhere from 1000' to 9000', elevation is a killer on performance. 3800' shouldn't be too bad, about 10% down on power.

19P prop "could be" appropriate, but the engine still needs to hit it's WOT RPM range, I'd shoot for the top end of 4600RPM for best performance. I have several different pitched props for different elevations (18P 4 blade, 16P 4 blade and a 15P 3 blade) so the boat runs well at elevation. If I were going to 4000', I'd bolt on my 16P 4 blade and watch the RPM's.

This?

Trol-A-Matic Trolling Plate

Yup

Also, adjusted the idle and got it down to around 700-800. I can get it lower... but I swear it will stall out if I do. As it is the motor seems to idle a bit rougher.

Gm 4cyl's idle a bit rough. With the engine warmed up, idling in the water and in gear, play with the idle mixture screws,,, and then the idle speed screw. As idle smooths with the mixture screws, you can drop RPM with the idle speed screw,,, but dropping RPM with the isle speed screw will put more demand on the idle screws and you'll probably have to readjust the mixture screws a "bit". If the carb is dirty inside (internally), getting decent idle at low RPM might be impossible. The ignition system also needs to be in good shape; plugs, wires, cap rotor and most important, points and condenser.

BUT - WOT appears now to be around 4600. I almost wonder if it just runs lower in the water??? Or... perhaps my prop pitch is a bit off.

When did you see the engine at 4600RPM? Out of the water and on the muffs.......? (if so, don't do that, not good for the engine/drive) WOT RPM is checked on the water, with a normal load (gear and people) in the boat.

The prop could be causing your low RPM issues, maybe tune-up stuff too. Exactly what prop do you have, part number (to figure out diameter and pitch)? I went from a 15.5x19P 3 blade prop (came on boat) to a 14.5x18P 4 blade prop and it was like a new boat, better in every aspect, holeshot, planing speed, top end. Not saying you need a 18P prop, but a different prop might be needed.

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

When did you see the engine at 4600RPM? Out of the water and on the muffs.......? (if so, don't do that, not good for the engine/drive) WOT RPM is checked on the water, with a normal load (gear and people) in the boat.

Doing that tomorrow. I figured everything would probably change on the water.

Carb very clean looking into it...

PO swore that all the basics had been done before he sold it to me. Cap, etc look to be in good shape. I'll give it another shakedown this weekend and see what happens.

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Did notice something else I forgot to mention... running at idle on the muffs last night I notice a "rattle" in the drive unit. I did have the drive trimmed up at first. I think it still did it while trimmed down.

Thoughts?

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Pardon the crude drawing... along with other things I need to figure out, at higher speeds, the boat does this while still going straight:



When I throttle down it levels back out.

Trim adjustment? Thoughts? I was pretty well balanced.

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Here's a good one! Been having some real issues keeping this thing running. Experienced an issue last week where I just suddenly lost power and wouldn't restart. May have found the reason?

Under the distributor cap:



Goop covering everything!



Chewed up wire, which I can't believe I didn't notice:



And the best, inside of the distributor itself, what appears to basically be powderized metal:



Any thoughts on where that may have come from? I haven't had a chance to replace all this yet, but my guess is that this is the source of my current starting problem...

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Ok, here's a good one. Expert advice would be appreciated. First, some back story:

Took the boat out Sunday. Ran well most of day. End of day, running at about 3k rpm, suddenly engine shut down. Could not restart. Engine turns, no start.

I figured I wasn't getting spark, discovered the above issues, fixed and verified spark.

I tried to start again today to no avail. I can give it a squirt of starting fluid, it runs for a split sec. Stops.

I seem to be getting fuel to the carburetor. I noticed, however, my gas wasn't very gas smelling. As a matter of fact, it seems to be very watered down, even at the fuel filter.

Aside from some jerk playing a poor joke with my parked boat, is there any way for a large amount of water to enter my system? How to proceed? If the vapor release were to drop below the water line, could it suck in water?

Thoughts?

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Self serving BUMP!

See above.

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

And... could the fact that our gas locally has 10% ethanol have any bearing on this?

 

[fishrdan]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Yeesh, not many replies here...

The powdered film inside the dizzy, no idea where it would come from, though I'd go looking for something worn. Looks like it needs points, condenser, cap, rotor, wires, plugs.

Water could get into the fuel tank from a bad vent and splashed water. Dump some fuel into a a glass jar to see if water separates from it. Probably a good idea to add a water separating fuel filter, $30 or so. If the fuel is contaminated, it's best to pump the tank dry, clean it out and fill with fresh fuel. If you have an outboard tank, you can hook that up to the engine's fuel pump and run the boat off the remote tank, to see if the boat's fuel tank or fuel has issues.

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Yeesh, not many replies here...

I've noticed.

Ordered a tuneup kit today. (Good value on iboats.com compared to locally!)

The splashed water thought occurred to me almost immediately. On the last trip out the boat was leaning very heavily towards the vent side of my boat. Could easily have submerged the vent. (Didn't get an answer to that yet either...)

I have a tank for an outboard. I found a pump in town that doesn't have ethanol. Gonna give it a shot! I'll let you know.

Thanks Dan!

 

[bonzoscott]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Can't imagine what caused the metal shavings in the distributor. Bushing is far below. Shaft doesn't wobble, does it? Listing of the boat at cruise: are you sure it's balanced? if water was entering the vent, should still be centered. But sounds like you have water in fuel by boat shutting down. I would have thought the water in fuel would have caused problems well before the end of the day. Just can't tell all of the circumstances from description.

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Can't imagine what caused the metal shavings in the distributor. Bushing is far below. Shaft doesn't wobble, does it? Listing of the boat at cruise: are you sure it's balanced? if water was entering the vent, should still be centered. But sounds like you have water in fuel by boat shutting down. I would have thought the water in fuel would have caused problems well before the end of the day. Just can't tell all of the circumstances from description.

The shaft does not wobble. Solid. I don't really see anything that could have been ground up like that, so I have no idea. There is some evidence that the PO had some work done on the oil pan and possibly the CAM in the past. Maybe he ground something down on the CAM itself and the shavings got pulled up into the distributor and he was unaware? In either case, the distributor seems to be functioning well. Just needs some tune up!

As it sits the boat is unbalanced portside due to the fact that the gas tank sits here. On my first trip out this wasn't an issue. Only had myself and one other person. This last trip I had myself and four others on board. Probably a bit unbalanced.

I think the water happened throughout the day as we were listing port side at higher speed. The tank vent is also located on this side. I'm thinking that when we were dropping to that side, water could have been getting into the vent.

Who knows? I still have to drain the tank, etc to see how much is in there!

 

[avpaulb]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Is there a resource for determining actual part numbers for this motor? I'd like to order the appropriate fuel filter, cap, rotor etc. The Service manual isn't helpful in this matter.

 

[fishrdan]

Re: 1975 Crestliner Trihull w/ 3.0L Mercruiser - New Project

Water shouldn't (shouldn't) enter through the vent if everything is run properly. Does the vent line run from the hull fitting, then upwards, then back down to the tank? It might have an upward loop in it. It needs the upward bend so water drains back out, instead of running into the tank. (Or it needs a newer style P-trap vent, if the vent line goes downward from the thru-hull fitting.)

Look up parts at Crowley marine with your serial number, they can be cross referenced back here or on the net. Those parts should be pretty standard and easy to look up.

I wouldn't be too concerned with using ethanol fuel, lots of people here use it without issue, me too. Though, if you got water in the tank or if it sat for a looong time it could separate. I would be concerned when it comes time for winter storage though, Stabil it.