Am I damaging my engine?

M

markrolf

Cadet
Joined
Mar 11, 2006
Messages
15
Hi,

We have a volvo/gm 4.3v6 carb (431A) which we use on the rivers in the UK. However, because of the low speed limit (7knots) the engine rarely breaks idle speed. In fact, if I remember correctly, we've only exceeded 1200 rpm once!

Anyway, is this doing any harm to the engine / electronics? Should the batteries charge?

The reason I ask is that we're considering repowering to a Volvo 3.0 4 cylinder.

Thanks,

Mark
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Am I damaging my engine?

It's not great to idle ALL the time, you might think about underpropping your engine so you have to run at 1200 to 1500 rpm to get to your 7kts speed. Even with a 3.0L engine, you don't want to idle all the time.
You would also get better charging at those rpms. You are charging very little (if any) at idle.
 
D

DHPMARINE

Captain
Joined
Dec 16, 2003
Messages
3,688
Re: Am I damaging my engine?

Were I to pick an engine to just idle it would be the 3.0L. A great work horse.

But you need more rpm's to battery charge.

I would follow Don's suggestion about under-propping,with either engine.

I am definetly not up to speed on Volvos,but Don can also advise you on changing gear ratios if you decide to change motors

DHP
 
M

markrolf

Cadet
Joined
Mar 11, 2006
Messages
15
Re: Am I damaging my engine?

Thanks guys, that's pretty much what I thought. I'm getting prices on a 3.0 this week, so dependant on how much it is, will most likely go that route.

Mark
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Am I damaging my engine?

Didn't even think about it before, but you better reconsider using the 3.0L engine. It was never used on the 290 style drive and transom shield. So you aren't going to find any parts available to adapt it. Such as exhaust system, raw water pump, engine bellhousing with intermediate bearings and shaft to attach drive to etc.
 
M

markrolf

Cadet
Joined
Mar 11, 2006
Messages
15
Re: Am I damaging my engine?

Hi Don,

I've been talking with my local volvo dealer who would install a brand new engine and drive. The transon shield is smaller than the 4.3, so they would also install an adaptor plate.

They reckon 30 hours as it includes brand new wiring loom too.

Just got to pay for it!
 
V

vipzach

Lieutenant
Joined
Feb 15, 2005
Messages
1,283
Re: Am I damaging my engine?

What is the reason you want the 3.0? You will spend thousands of dollars going to the smaller motor. If you just under prop your 4.3, is the gas savings going really justify the large amount spent to get the smaller engine? Or is there another reason for the change?
 
V

vipzach

Lieutenant
Joined
Feb 15, 2005
Messages
1,283
Re: Am I damaging my engine?

bjcsc said:
$5000 repower vs. $500 prop? I don't get it...
Click to expand...


I bet he spends more than that for the repower and not that much on a prop! But that is exactly my point in my other post.
 
C

calwldlif

Petty Officer 1st Class
Joined
Aug 16, 2002
Messages
348
Re: Am I damaging my engine?

Would a sea anchor do anything
good?
I agree the propping to allow
higher revs is the way I would go,
hell i do that know.

Sounds like a beautiful area to boat,
cruise.

No planing areas?
 
tommays

tommays

Admiral
Joined
Jul 4, 2004
Messages
6,768
Re: Am I damaging my engine?

Dont forget he is laying out 7 dollars a gallon for gas :^

i would just do a prop BUT a 3.0 would save a LOT of fuel money just kicking down a canal at 7 kt


Tommays
 
M

markrolf

Cadet
Joined
Mar 11, 2006
Messages
15
Re: Am I damaging my engine?

We really need to change the engine. Fuel has gone mad in the UK, and can cost the equivalent of nearly $10 a gallon.

Anyway, we're having a lot of problems with starting, overheating, electrics etc etc, and to be honest, it just seems the sensible thing to replace the lot!
 
QC

QC

Supreme Mariner
Joined
Mar 22, 2005
Messages
22,783
Re: Am I damaging my engine?

I agree with hystat although I'd put a small diesel OB on it. You could actually get a payback on a smaller purchase like that . . . How many hours do you run the boat per year?
 
bjcsc

bjcsc

Lieutenant Commander
Joined
Jun 1, 2006
Messages
1,805
Re: Am I damaging my engine?

markrolf said:
We really need to change the engine. Fuel has gone mad in the UK, and can cost the equivalent of nearly $10 a gallon.

Anyway, we're having a lot of problems with starting, overheating, electrics etc etc, and to be honest, it just seems the sensible thing to replace the lot!
Click to expand...

Wow! Didn't know about the current engine problems but in consideration of them, the repower is probably the way to go given only the two choices. I would be checking out whether or not a diesel repower could be accomplished. All this depends on how much you like your current vessel (don't know what it is). Me, I'd be looking at fixing what I had, disclosing what I couldn't fix and selling, and then buying something with a diesel, probably a sailboat or a powerboat with a diesel outboard.
 
R

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Am I damaging my engine?

they als make a device called a back troller that is designed to work similar to a sea anchor at low speeds and flip out of the way at high speeds, you will not find a lot of speed difference at 650-1500 RPM between the 2 engines.
 
C

calwldlif

Petty Officer 1st Class
Joined
Aug 16, 2002
Messages
348
Re: Am I damaging my engine?

Do you attribute the problems
to low rpms?

10 dollars a gallon? Gulp:%

6 Cyl to 4 cyl hum

4.3 to 3.0
that is a reduction.
You will still have to gear and prop to
run a respectable rpm.
I don't know if there available and (usually
reduce not increase)or whether you can fab
them but it is different size pulleys.
There are under size pulleys for some performance
engines that will reduce horsepower loss and
reduce rpms that pumps, alternators, ect. spin
The same technique could be used to increase
rpms of pumps, pulleys ect.
I am trying to state that an engine swap
by itself will not fix the idle speed issues your
having.
I feel you need to get the rpms up on whatever
motor you go with.
how much is Diesel going for?
 
P

paulie0735

Chief Petty Officer
Joined
Dec 6, 2005
Messages
463
Re: Am I damaging my engine?

OMG! Your gunna throw away a perfectly good engine just because it’s a bit fouled up from running rich all its life and the cooling system needs a service. Are you serious?? Get it tuned and serviced and a smaller alternator pulley fitted, take it for a run on a lake somewhere and clear its throat, get it up to proper operating temp and work it. Than get the smaller prop so it’s pulling a free and easy 1200 - 1400 rpm, the same engine in a car spends 80% of its life below 2000. Take this advice and you just saved yourself enough cash to run the thing for the next 5 years............... or sell the thing and buy something with a small 4 stroke outboard.
 
You must log in or register to reply here.
Top