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Volvo penta AQ120B270

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sierrah

Member
hello hows things?. iam new to

hello hows things?. iam new to this place and have looked around for other answered questions.

i know about boats and engines but only as much as ive learnt myself and common sence (which really dont help you guys lol) i tens to use my knowledge of car engines and apply to a boat within reason

to cut a long story short my engine isnt running properly.heres the problem

it seams to me - when the engines fired up and warmed up it will tickover like normal. when i rev it there is a slight delay but im guessing its because its got a carb and not an injected engine. but ither way it will rev nicely and all the way. the problem begins when you drop it into gear. it seams when the engine is under load it wants to die and when it does eventually go its like there is fuel starvation. the max the boat will run is upto 2500rpm area. the boat is quite old i think its 1971.

imagine driving a car and just before you run out of petrol it pulls back alot and the tone of the engine goes deap. (but it will idle ok) this is my boat lol.

i have changed the points (dont know about timing ect as im not to clever with it)
i have changed the plugs and leads
ive changed the dizzy cap and rota arm
ive changed the inline fuel filter (the big one lol)

i have taken off and looked at the fuel pump. its a mecanical one and ill seams ok

have changed the standard alternator which was 30aph and brought a new 70aph which now keeps the batterys nice.

have replaced 2 x 110amp batterys / now new

changed the fan belt
think thats it off the top of my head.
couls really do with someone looking at it that knows.(marine engineers are really expensive)
please ask and ill try answer what i can.

have owned the boat for a couple of years. brought it off a south african guy down brighton marina. he did alot of the work himself on it (which was even worse than my attepts lol) to say the least even i would say it was bad.

anyway sorry to bore you with a long post. hope i have given as much info as possible and i hope to speak with you all soon

:eek:)
 
"Hi Brian, Seems you have chan

"Hi Brian, Seems you have changed a few items on your engine. Was this because you were having the problem you mention or did the problem start after the changes? Was the engine running properly recently? How long ago? Did this problem start abruptly or did it come on gradually, over a period of weeks/months?

You should get hold of a compression tester, do the compression test then post your results here. We'll go on from there."
 
started slowly having the prob

started slowly having the problem so changed the tings i did bit by bit.

the engine used to run ok last year. even then it still maxed out at 3000rpm.pulled back like fuel starved. but other than that ran ok

problem started gradually couldnt say how long

will look for compression testers. any tester im guessing?
will get it and test it and get back to you

thankyou
 
try checking the carb i had th

try checking the carb i had the same problem with bad gas that had been in the carb for a while also check the point gap jets on the carb might be clogged due to bad gas or not completly clogged just enough to get that starving sound. good luck hope it doesn't cost to much to fix
 
yea i did think about that. so

yea i did think about that. so heres what i did.

i took the carb off and cleaned the metal mesh air filter thing as best i could. i then took the whole carb apart being very careful. i then took it to the local garage and used the airline to try and blow the jets out. then put everything back together "with no screws or anything left" lol
all back on the engine...and its a little worse lmao

does anyone live near bournemouth or poole
 
Hi if you have only ever been

Hi if you have only ever been able to get about 3000 rpm it might be that you are over proped what size prop do you have on? Also check your timing.I would recomend doing away with the points a fitting a contactless ignition system. i bought on of ebay for £25.00 deliverd.
 
hiya. the engine revs over 300

hiya. the engine revs over 3000. would prob rev all the way around. but not once its in gear

the prop was brought from a volvo penta dealer so im sure that its the right size.

thanks for that link gonna go have a look and knowin me buy lol.

will still keep you informed with the compression test :eek:)
 
"By right size, did not mean p

"By right size, did not mean proper fit. Props for boats have two "measurements" Diameter and Pitch. Diameter, is obvious, Pitch, less so. Pitch is the number of inches that a prop would advance in one revolution if it was turning in a media that did not allow any slippage. I don't see where you mention the size and type of your boat. If either the diameter or pitch are incorrect, they can cause the motor to not reach maximum proper RPMs ( or exceed allowed maximum). By and large, Pitch is a greater factor. For every boat size, hull configuration, boat weight, engine horse power and drive reduction ratio there is only ONE correct prop size and possibly one other that will work "OK"."
 
ill get the information on tha

ill get the information on that just to check. volvo penta supplied me the prop based on engine and boat
 
"Did the engine ever top 3000

"Did the engine ever top 3000 rpm while in gear since you have had the boat? If so, what was the max? Can you see numbers stamped on the prop, something like "15 x 15" for example? If you can see them, what are they? Finally, what make of boat do you have and how long is it?"
 
"no the max ive ever had the e

"no the max ive ever had the engine was 3000 rpm.
cant see the numbers if any on the prop as its under water and the engine lift dont lift that high,

the boat is a 21ft waveryder. will try get pics if i can put them on here"
 
"these were taken by the old o

"these were taken by the old owner when he was advertising.
please note that the picture taken of the engine "was not" taken by me but the "old" owner.
i wonder who will comment first lol
218221.jpg

volvo penta AQ120B/270 outdrive
218222.jpg
"
 
"AQ120B are supposed to be abl

"AQ120B are supposed to be able to rev up to 5000 RPM at WOT with the correct prop. Unless the Volvo dealer really screwed up, the prop that he gave you should at least come close to what the optimim prop should be plus or minus one pitch size. This "range of error" does not account for 2500 (or even 3000) RPM vs. 5000.

As to checking things, a couple of things tht don't require tools... I noticed that you changed the "dizzy" and the cap. When you changed the "dizzy" did you check that the spark advance mechanism worked? (You should be able to turn the dizzy by hand in one direction only a few degrees and when let go, it should spring pack.

Also check and double check that the firing order is correct, i.e., that the spark plugs are connected correctly at the distributor cap. Very critical on 4 cyln engines. Find a manual and check against the manual, not just that you put it back the way it was....

http://www.volvo.com/volvopenta/na/en-us/marine_leisure_engines"
 
i changed the plastic cap and

i changed the plastic cap and rota arm i didn't change the bottom part that goes into the engine.
there is a bolt bixing the dizzy in place and when you loosen it you are able to turn the hole unit. have done this and its in the best position for running properly. if you understand what i mean lol

now you mention about the leads bein on the right way around lol. i had a simular prob with the car. eas all lumpy and sounded like it was fireing on 3 not 4. turned out the leads were on backward .

i will look at the manual and check it. does anyone have a picture i could copy the lead pattern from.
 
"What I was specifically refer

"What I was specifically referring to is rotating the rotor arm itself. There is a mechanism, operated by centrifugal force that moves the rotor arm itself relative to the shaft that the rotor arm is mounted on. If this is frozen in place or sticky, engine will not run well at all. With the cap off you should be able to twist the rotor arm itself in one direction about 10 degrees or so and have it snap back when you let go."
 
"While there are probably some

"While there are probably some who are able to set the timing by ear, I don't know any. I'm a firm believer in timing lights and compression gauges and not necessarily the expensive types. You will get a lot of use out of them maintaining and analyzing problems with your older engine.

From what you say it sounds like your engine is over-propped but that would not account for the recent deterioration in its rpm performance. However, sooner or later you are probably going to have to get at the prop and see if it is the proper diameter and pitch for your boat/engine combination. 3000 rpm is not what you want even with a good running engine under load."
 
ill have ago at rotating the r

ill have ago at rotating the rotor arm itself.
im hoping to have a compression test tom eve so will give you results for that and go from there.
chacked the leads and they are correctly fitted.

its bugging me cos the engine (once started from cold lol) will idle nicely and it will sound nice.

anyway watch this space. :eek:)
 
"My guess looking at the pic,

"My guess looking at the pic, You will probably be lucky hitting 20 Mph. This would indicate a prop: 14x15, 15x13 and if extreme lucky 15x15. Anything else and You will be far out, My guess will be 14x15.
(Volvo). Suggest You find out what You have on the drive before messing around with the engine. If not stamped at the side of the hub, remove the prop and look at the end under the cone unless the one selling You the prop may tell what he sold!
Even if the drive does not lift the prop out of water, no problem. You just get slightly wet!"
 
"I agree you will be very luck

"I agree you will be very lucky to get 20mph in a boat that size. I would say that you are way underpowered with a 120 hp engine,I would have thought you would need twice that power to get any sort of performance in a boat that size and weight."
 
"slightly wet? in about 10ft o

"slightly wet? in about 10ft of water?. ill drown lol but i will find out

I agree you will be very lucky to get 20mph in a boat that size. I would say that you are way underpowered with a 120 hp engine,I would have thought you would need twice that power to get any sort of performance in a boat that size and weight.

this aint sounding good lol.
will get back to you asap

ps its a petrol engine"
 
"I have a AQ120B 270 on a 17 f

"I have a AQ120B 270 on a 17 foot boat. Top speed 43 km/hr with a 15X12 prop, top rpm 4300. Yes it sounds like you are underpowered."
 
underpowered with the engine y

underpowered with the engine you mean?. you think i need bigger?

and the prop NEEDS to be 15 x 15?

can anyone point me in the right direction for bigger engines
 
"It would be a little less exp

"It would be a little less expensive to try (borrow from a prop shop) a 14 x 15 or a 15 x 15 prop for a test run than it would be to run out and buy a bigger engine.
wink.gif
"
 
"That's a good question. U

"That's a good question. Usually the best places are VP marine shops (most of them have boneyards of some sort), marinas, and prop shops. Don't know what is available in your area, you you will have to do your own research."
 
"right i found the prop size &

"right i found the prop size "without" getting the slightest bit wet! ""wow how? i hear you ask"" lol
i found the recipt. how clever am i? lol

prop size is 15 x 17.

the propeller-rh 15x17 361top product code 814616 price £171,96"
 
"If You add 200rpm for every 1

"If You add 200rpm for every 1" pitch reduction, and add 100 rpm dor any 1" dia reduction You might end up something like this.
Min max RPM 4500 -max obtained RPM 3000 ='missing' 1500RPM!!! In theory You have to reduce pitch by 7" and dia by 1"! giving a final result of 14" x 10".
I do not think You will find anything like that.
Volvo has 14 x 13 and 15 x 11 in the assortment. I would have tried a 15 x 11."
 
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