Volvo Penta 3.0 poor idle and acceleration - can we do better?

[dweigle]

I just bought a used 1998 Glastron with a Volvo Penta 3.0 L/Cobra SX sterndrive. It has a rough idle at 700 RPM's but idles higher and a little smoother at around 1000 RPM's once warm. The whole boat shakes. It has a Hustler 14.25 x 21 3-blade prop with barely a scratch on it. The boat was hitting 4100 RPM's and 36 mph with two people at WOT half trim (as high as the prop would allow without spitting up water) when I bought it. It also had/has a very poor hole shot. Since then, I ever so slightly advanced the timing on the distributor, sprayed out the carb with a whole bottle of cleaner, changed the fuel filter by the fuel pump, changed the plugs (Autolite AP104 set to 0.045 - please let me know if this is a problem - I got the x-ref on sparkplugs.com), and added fuel injector/carb cleaner to the gas. I adjusted the idle screws but cannot get rid of the 1-2 inches back and forth shaking of the engine whether it is cold or warm. The distributor cap and wires LOOK great, and the guy I got it from said they were replaced this year and he is a mechanic. The boat always starts right up and planes in about 6 seconds without a skiier with very little lifting of the bow. I should mention it has a doelfin. The boat pulls very hard in either direction. There's that little metal fin on the back on the motor that I cannot loosen to adjust, but that is quite crooked by about an inch.<br /><br />The problem is that it cannot pull up a skier above 200 lbs and pulls me up on slalom (185lb) only after drinking half the lake 30 seconds later.<br />I read that these can cause poor acceleration while towing:<br />-exhaust clogged with flapper<br />-base timing off<br />-bad plugs<br />-advance timing off (is this setting the gap?)<br />-motor height is too low (flat plate should be 1-2 inches above bottom of hull.)<br />-clogged fuel filter (by fuel pump)<br />-clogged fuel filter (in/by carburetor) what wrenches loosen this nut?<br />-prop pitch is too high or not enough blades<br /><br />Is 37 mph and 4200 RPM's typical for this boat, or what should I be seeing? Should I focus on engine tuning/troubleshooting like the things in the list above, or is this all the power I can get and I should just get a different prop (an 18" pitch 4-blade or a 19" pitch high five)?

 

[dweigle]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

I forgot to mention that this is a 175 SE. Other posts are saying this boat when new can do about 42 MPH at 4500 PRM with a 14.5 x 21 pitch 3-blade prop.

 

[Sooner44]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

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[Sooner44]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

I have the same set-up. 175 SE with 3.0 SX drive.<br />First off, your boat should be running 4400 -4800 RPM @ 42-44 MPH WOT. Your low on Rpm, either the carb throttle linkage is not adjusted right, which I suspect, or the prop is throwing it off.<br />Standard prop on your boat is a 14.25 X 21 pitch, so I think your good on the prop. Only other adjustment is to make sure the linkage is opening up the carb all the way. Have you tried this ??<br />Once you get the RPM up to at least 4400, then start on the rough running engine. You will probably find the problem lies with your carb.<br />If the previous owner let this boat set very long with gas in the carb, you will get exactly what your describing. Same issues with my 3.0 SeaRay that I let laquer up one winter. Try this and if all fails, take it to a reputable boat shop.

 

[dweigle]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

Thanks Sooner - I hope this is the magic bullet. I forgot to add the infamous carburetor to my list. The guy I bought it from was a young mechanic who said the carb was sticking at times. It is possible that it is clogged (despite the whole bottle of carb cleaner). <br />I am unfamiliar with the correct orientation of the carburetor throttle linkage. I ordered a 1998 Volvo Penta book which might detail it, but it hasn't arrived yet. Know of any places with diagrams for a holley 2bbl? Or could you send me a picture of your carb? dweigle@comcast.net or put it here if you can post pics.<br /> <br />Thanks again for the advice -- I'll definitely have a seasoned mechanic look thoroughly at the carb. I would rather put the money into getting the engine running at peak performance, but if all else fails, I'll probably try a ronhill signature five 19 pitch.

 

[Sooner44]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

OZ,<br /><br />Just get someone to move the throttle back and forth, while you view the carb. You will see the linkage moving on the carb. There will be a small lock nut on the threaded part of the linkage where it attaches to the carb. Remove the cotter key and small washer fron the carb. post, and see if you can move the carb plate further forward.<br />If so, adjust the linkage out in the direction of more throttle, and lock the linkage down with the nut, and place back on carb, the same way you took it off. This procedure is VERY simple. Just push the throttle handle all the way forward, mark where the forward most position is on the carb, disconnect linkage and see if you can get more out of it. I'll post pic when I can. I wouldnt be so quick to replace the prop with a non factory pitch prop just yet. As I said, I have the exact same set up, and my 21 pitch will do about 4500 -4600 rpm, so yours should too.

 

[Purebreed]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

The tab that you are refering to is supposed to be off senter to help counter act tourque steer from the rotating prop. The 3.0L motors do have a tendancy to idle rough. I also agree that your rpm is low for that set up. A 19 pitch may help bring the rpm up 200 or so.

 

[whywhyzed]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

changing the pitch and bringing the rpm's up doesn't usually make a boat go faster. It makes the boat go the same speed, but at a higher engine speed.<br /><br />Increasing the prop HP via a tune up or repair is the solution.<br /><br />You may also want to make sure the boat isn't heavy due to 1000 pounds of water under the floorboards, or a waterlogged hull.<br /><br />Then tune the engine up. <br /><br />You would want to pull the plugs and do a compression test as well as inspecting the spark plugs for evidence of problems.

 

[dweigle]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

Sooner, I now know exactly where you are talking about with the carb linkage. Thanks, I am heading to the lake tomorrow to check this out. Also, I'm changing the inline filter in the carb. I really want to believe you that this boat can do 42-44 mph with a 14.25 x 21 prop. I am staying awake all night thinking about it.<br /><br />Purebreed, thanks for letting me know to keep the metal fin angled. The steering must be getting screwed up by the doelfins. If I let my hand off the wheel at WOT, the boat pulls VERY fast and hard to either the right or the left, depending on its mood. If I were to let go, the boat might roll, wahahaha.<br /><br />hystat, bilge pump is actually working and I checked for water. It is mostly dry. I will be doing a compression test tomorrow and I almost hope I find something. Don't know which is easier, that or a carb rebuild. The plugs were mostly clean with a small narrow brownish carbon ring around the middle. I think they were almost new but I replaced them three weeks ago with the autolite platinum 104's (which could be a problem but nobody seems to know for certain).<br /><br />Does anyone think this could be a gear ratio problem? For example, 1.84:1 rather than 1.97? (It is supposed to be 1.97 right?) I'll check that too this weekend.<br /><br />At lastly, anyone want to go skiing? You just need to bring the gas....hahaha

 

[Sooner44]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

Good luck OZ, report back what you find, it will help the rest of us ! Also, get rid of those aftermarket doelfins if they are affecting the steering. I dont have any, and mine steers straight as an arrow. The Glastrons are known for planing quickly, you shouldnt need them. If I was in your position, I would return the boat to 100% stock configuration.<br /><br />Sooner

 

[dweigle]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

Well, I took 'The Oz' for a spin today with three people in the boat and it actually pulled me out of the water on slalom in about ten seconds instead of 30! It also pulled up a 225 lb skier quite fast for the first time. Trouble is, I have no idea what the difference is except last weekend I cleaned the carb with a can of carb and choke cleaner, changed the fuel filter on the fuel pump, put in another prestone fuel injector cleaner additive in the gas tank, adjusted the idle mixture screw outward, and put a silica gel dessicant in the motor area by the batteries to dry things out.<br /><br />The really crazy part is while the hole shot is better (minimally acceptable), it is only going 29 mph max at 3900 RPM with a 220 lb skier on two skis. And with no load, it is still doing only 34 mph at 4100 RPM's with four people. Maybe this is normal?<br /><br />I checked the carb linkage: first I removed the cotter pin, then I checked the movement of the throttle and where it moved the hole in the cable to. Basically, when everything is connected, the throttle does not go the whole way down because cable's movement is being limited by the carburetor. When the pin on the carb plate is disconnected from the hole on the cable, the WOT position puts the cable about an inch behind the farthest place the carb plate pin will rotate to. When I move the throttle to idle, the hole and pin just about line up. Is this okay? This arrangement seems like WOT will try to force the carb past its physical limit.<br /><br />Another note about the carb - when I remove the flame arrestor, the flapper on the top is all rusty. It is positioned on about a 45 degree angle and seems to have about 1/4" of play.<br /><br />I looked at the old spark plugs again. The one is smoked black all over but the gap looked way small. Two looked almost new. The last one looked brown. All of them were rusty on the part that sticks out of the engine (put not on the connector).<br /><br />I ordered a fuel filter for the carb and it is this small porous golden metal cylinder with a cone in the center with two gaskets. WHERE DOES THIS GO? I unscrewed the fuel line from the carb and there is just dead space there, no filter or nothing. I thought that's where a filter of some sort should go...<br /><br />If I get out tomorrow again, I will try to take off the doelfins, check the check valve by fuel pump for dirt, check the fuel line screen going up from check valve, check the gear ratio, and double-check the prop's condition. I am almost thinking there was once a problem with water in the pistons the way everything is rusty. is there anything else I should try? Maybe a quick compression test is in order?

 

[dweigle]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

I almost forgot, I did advance the timing last week about 1/16" to 1/8" of a rotation counter clockwise from where the marks were etched on the distributor during its previous ownership. The engine idled about the same but added 100 RPM's on the top end last weekend. I know it's not always wise to tinker with the timing but it could have helped that hole shot.<br />And I forgot that hystat said to check compression too. Where do I get a cheap yet functional gauge? What is it called exactly?

 

[Sooner44]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

Well, all plugs should be same color. A compression test would be recommended. Rust in the carb, would suggest wet fuel, or water of some sort entering the carb. this is not good !<br />Rusty plugs are a sign of moisture also. Get a timming light and set the timming per spec's, don't guess at it. The butterfly on the carb, will settle at about a 45 deg angle when cold, after engine is started the heater in the choke assembly will heat up and fully open the butterfly, be sure and check this when engine is hot. You may have water in your gas tank ? You may have a blown intake gasket. You need to get this checked out to protect your investment. Take it to a good BOAT mechanic and pay him to diagnose all problems, then if you want to fix it, take it and fix it, or if his price is in your budget have him fix it.

 

[dweigle]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

I asked the seller about compression and he said it was great when he tested it recently this year. I don't have a compression or vacuum gauge, but I did pull the spark plug wires one at a time and it seems like the two cylinders toward the back of the boat are not really firing. I think it is getting good spark, at least I was getting zapped pretty good. I think I'll take it to the shop next spring.<br /><br />p.s. for winterizing, all I did was run three gallons of antifreeze through it when it was warmed up, stalled it out with anti-fogging oil in the carb, put in fuel stabilizer into the gas tank, and stored the stern drive almost all the way down. And I pulled the hull plug. Must I also pull other drain plugs like for getting the coolant out?<br /><br />Thanks,

 

[dweigle]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

Okay I got it back out of storage this year. She started up and ran pretty rough. I quickly noticed that gas was leaking out from the float assembly around the green gasket. I removed the float assembly (4 bolts) and tightened the bolts to squeeze the gasket. One bolt was stripped. I managed to tighten the others enough to stop the leak. I changed the emgine oil and the stern drive oil.<br />I did a compression test and each cylinder was between 170 and 180. I replaced the plugs with the exact AC Delco marine plugs specified at the 0.045 gap. I adjusted the idle speed down to 600 RPM's using mixture/idle screws and a timing light/tach and checked the timing @ 600, which was 12-14, so I set this to about 6 - 8.<br />The idle is now smooth and there is no smoke coming from the engine. I put a new Ron Hill 19 pitch 5 blade signature prop on and it now hits 4600 RPM at wide open throttle. However, the speed is still at the low end, around 36 MPH. It pulls me up on slalom much much better. However, it will not pull me any faster than about 28 - 29 mph - it is WOT to pull me at a decent speed. I'm still thinking that this boat should go at least 33 with a skier and more around 40 mph without.<br />The one thing I noticed is there was a small amount of water in the engine oil when I changed it. And afer I changed the plugs, water was shooting out from around the back plug. When I removed it, cleaned the threds, and put the plug back in, everything was okay. The two plugs toward the back of the boat were covered with black carbon soot after just 20 minutes of idle, where the two at the front were clean.<br />Any ideas?<br />Thanks,

 

[bruceb58]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

First off, I would be concerned about this water you noticed. What do you mean when you say "And afer I changed the plugs, water was shooting out from around the back plug"? <br /><br />A little water in your oil may be ok if it was cause by condensation from the storage during the winter<br /><br />Looking at your other posts from last year, I would probably look into having the carbureator rebuilt. Now when you say you had a float problem and a screw stripped, I would say definitely have the carb rebuilt because now you have a safety issue. If you have someone rebuild your carb, you need to mention the stripped screw ahead of time becase your carb body may be toast.<br /><br />Regarding setting the timing, It is very possible that you have a distributor that requires you to turn off the electronic spark advance before adjusting timing. What model number motor do you have? Your model number should be on a tag near your oil fill cap.<br /><br />The doelfin may help you plane faster but it will hurt your top speed becasue it adds some drag.<br /><br />Which manual do you have? Please don't tell me its a Clymer or a Seloc.

 

[dweigle]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

Thanks for the reply Bruce.<br /><br />SORRY I have both a seloc and clymer manual! The seloc is the wrong years so I don't use that much, but the Clymer is right and is much better. What do you suggest? What is better in the one you like?<br /><br />The biggest problem at this point is top end POWER. I get 36 MPH (no tow) with a 21 pitch 2 bladed prop at 4000 RPM or with a 19 pitch 5 blade prop at 4600 RPM. It's like I am about 15% short on the HP I ought to be getting. Would a carb cause this? Or maybe a head gasket leak?<br /><br />I mean exactly what I said about the water leak - I pulled out all the old plugs from last season and put new ones in. Once I started the engine, water was squirting out from around the threads of the back spark plug like a water fountain. Sounds insane but true.<br /><br />I have the same feeling about the carb needing a lot of work. The last guy who owned the boat said he got 40-45 mph from the boat but said the carb was always "sticking". What does this mean? <br /><br />Sorry I cannot check the model # of the engine because it's 3 hours away.<br /><br />I removed the doelfin and the nose of the boat definitely shoots up in the air now but only for about 7 seconds even when pulling a skier. I like it better without the doelfin but I can see why you might want it with a different boat.<br /><br />Still having trouble with the steering jerking way hard to the left and sometimes to the right. Maybe that is just a feature of this boat and hull design. Maybe trim tab adjustment would help but it pulls both ways so I don't know. That darn screw is practically melted on and won't budge.

 

[bruceb58]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

You want the Volvo manuals. When you look for the manuals don't do what I did and go by the year of the boat. You need the "series" number that is noted in the model number. You can read this on your valve cover.<br /><br />It will probably be an "LK" or a "BY"<br /><br />My model number looks like this 74GL PLKD<br /><br />The P designated power steering and the D designated DuoProp. The middle two letters are the engine series which is what you want in order to get your correct manuals.<br /><br />Look here for an example of engine model numbers vs year:<br /><br /> http://www.marineengine.com/manuals/volvo/ <br /><br />My boat is a 1998 boat yet has a 1997 "LK" engine.<br /><br />Have you looked at your oil since you have been running it this year?<br /><br />I see you are playing around with props. Have you ever used the Volvo prop that you boat/engine combo came with? Props like you are using are more than likely good at one thing and not another. It would be nice to have a baseline with your stock prop.<br /><br />You were mentioning you weren't sure if the throttle linkage was correct. With your engine off, put you hand control to full throttle. Look inside the carb and see what position the throttle plates are in. Are they straight up and down?<br /><br />When the engine is warmed up, is the choke plate all the way open.<br /><br />I am just mentioning a few things to look at. Obviously, there are many things I haven't even talked about like ignition, fuel filters. All those things need to be right and they need to be kept up with proper maintenance.<br /><br />Good luck.

 

[dweigle]

Re: Volvo Penta 3.0 poor idle and acceleration - can we do better?

Thanks for the website for the manual. I have a "BY" engine (1998 3.0 GS SX). I had no idea it would cost $72. Are you talking about the Workshop manual?<br /><br />I don't have the original Volvo prop because I bought used. It would be interesting to see how it would compare. I want to see the Ron hill prop in a 21 pitch but I don't have another $335. Cannot believe the RPM's changed 600 RPM going from 21 to 19 and 5 blades to 3.<br /><br />I checked the spark in each wire and each one is firing consistently. Fuel filter was changed end of last season. Not sure if there are more than two fuel filters (one by carb and one sort of canister shaped near distributor).<br />I have a vacuum gauge. Wonder what can I check with this?

 

[dweigle]

Resolved mostly: Volvo Penta 3.0 poor idle and acceleration - can we do better?

Resolved mostly: Volvo Penta 3.0 poor idle and acceleration - can we do better?

1. I thought only the prop was bent last year my second time out (late May '06) but was I ever wrong. The drive shaft was also bent - almost an inch. Dad and I straightened this out using a little car jack, a small screwdriver to rotate the shaft through the cotter pin hole, a 2 foot or so stick for measuring the wobble, and a cloth to protect the splines. We put a cloth doubled up over the prop shaft and the jack between what I think is the antiventilation plate and the prop shaft, which was positioned with the high spot facing up. Very carefully it took about 10 "spreads" to straighten the prop shaft in this way.

2. I examined the lever going from the throttle plate to the choke's fast idle cam. The level was on the top of the cam. According to the manual, the linkage lever should be under the red cam. Is this correct? Or should I have simply kinked the linkage to shorten it and kept it on top? I moved it to be underneath just because I am by the book but my Dad said it was fine where it was. Sometimes I like to be defiant like that.

3. I re-adjusted the mixture screws and idle screw, which were not too bad. I rechecked the vacuum, which is a little low at about 16.5 and perfectly steady for several seconds, then it shakes about 1 or 2 units and gets steady again. Maybe it is how I'm butting the vacuum gauge hose next to the vacuum hose, who knows.

4. I checked for vacuum leaks with an unlit propane torch. No problems obvious.

5. I checked the carb and the manifold mounting screws/bolts and nuts against the torque in the manual. Some needed tightened quite a bit, and I thought they were stripped until I tried turning with a shorter non-torque wrench. How surprising, a torque wrench gives torque. Dad always said use the right tool for the job.

6. One of the screws at the carb's accelerator pump level WAS found to be stripped last year. I found a new screw this year and it tightened up much better, but I didn't want to overdo it in case the hole threads were also stripped.

7. I poured some mystery oil and sea foam into the crankcase and the fuel (half as much as directed for each)

8. We launched the old Oz on May 27, 2007. Beautiful day except for a late thunderstorm! With 375 lbs of people in the boat, one less battery, the same straightened five blade 19 pitch prop as last year, clean but unwaxed hull, and no extra gear, she ran at about 38 mph at 4800 RPM at optimal half trim. Yes I'm dangerous with those RPM's but it was good to be out there again!

It looks like Sooner's advice about making sure the throttle plate opens fully, along with others, finally reclaimed the 10% I was looking for!

Final results:

Aug 2005: "4100" RPM's and 36 mph, on 3-blade 21 pitch Hustler
May 2006: 4600 RPM's and 36 mph after timing/tuning/cleaning, on 5-blade 19 pitch Ron hill
May 2007: 4800 RPM's and 38 mph after moving carb to fast idle cam linkage below cam so throttle plate opens fully, on 5-blade 19 pitch Ron hill

Should have listened to Sooner44 much sooner - I would have bought the right 21 pitch 5-blade prop had I taken time to tune up and inspect the boat better.
Also, Sooner44 and bruceb58 were right about being concerned about the throttle linkage, but I don't know whether moving the throttle plate to cam linkage under the fast idle cam was the thing to do. At least now the throttle place opens.