Boating - June 2016 USA

Q&A

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By Michael “Mick” Hannock

Attitude Adjustment

[ Q ] Dear Doctor, I have a 2003 SportCraft

2 72 hardtop powered by a 300 hp MerCruiser

5.7L MPI that connects to a Bravo Three drive

with a jackshaft. The gear ratio is 2-to-1, and

I operate the boat with a full load most of the

time, so I run a 20-inch-pitch set of props.

Overall, this is a satisfactory setup, but during

acceleration from a stop, it feels like there’s a

f lat spot around 1,500 to 1,800 rpm. The engine

runs smoothly prior to reaching and after hitting

this rpm range. I performed a complete tuneup,

including spark plugs, wires, distributor cap,

rotor and fuel filter. This helped for a little while,

but the problem returned.

I have had several technicians check out the

engine, and they can’t find anything wrong. This

problem has existed since I bought the boat. The

engine has more than 2,700 hours on it, with

no other problems. I service it every 90 to 100

hours with oil, filters and anything else that

is required.

CAPTAIN JIM

Via email

[ A ] If the boat experiences significant bow

rise while accelerating, the problem could be

a lack of fuel until the boat planes off. Borrow a

fuel-pressure gauge and measure pressure at

the Schrader valve at the fuel rail. It should

measure a minimum of 32 psi at all times. If

the boat doesn’t

have trim tabs,

you might want

to get some and

lower them when

planing so the bow

rise isn’t as bad.

To Run or Not?

[ Q ] Mick, in the March issue (“Flush”), I was

surprised to read that the motor has to be

running to f lush the MerCruiser. I have two

Volvo Penta 5.7 motors in salt water. When

Any marine

surveyor will

have a story

about boats

sinking because

of muskrats.

Muskrats and

minks can’t resist

nesting in an

inboard’s exhaust.

This can cause

a blockage and

overheat, which

burns the hose,

or they’ll chew

through the hose

to get into the

boat itself. Either

way, a sinking

is likely. Check

your exhaust hose

and outlet for

signs of rodents,

and consider

installing guards,

like the Muskrat

Otter Exhaust

Guards at

hurleymarine

.com. — Kevin

Falvey

I’m back in my slip, I usually connect the

freshwater hose to the motor and start it

right away for five minutes, then leave the

hose connected for another 10 minutes.

I don’t know if that is correct. Could I

just leave the hose connected without

starting the motor? I bought my boat used

and never had the instructions for the

motor. Where can I get a manual for

these engines?

UDO REELITZ

Lecheria, Venezuela

[ A ] It’s always best to check the

manual for a specific make, model and

year of an engine before coming to any

generalizations. Here is a web address

where you can search for and download

Volvo Penta owners’ manuals as PDF files:

volvopenta.com/volvopenta/global/en-gb/

marine_leisure_engines/parts_service/

publication_search/Pages/publication_

search.aspx.

Restricted Exit

[ Q ] I have a 1993 Sea Ray 300 Weekender

with twin MerCruiser 5.7L Bluewater

inboards with freshwater cooling and

V-drive transmissions. I’m having a

problem with my port engine’s inboard

exhaust hose (the longer one) getting very

hot at idle. Once it gets to cruising speed,

it cools down enough to touch. The water

pump and housing on the port motor were

replaced, along with the inboard exhaust

hose. Additionally, the inboard manifold

has been replaced, and the heat exchanger

was back-f lushed in 2014. Finally, the

inboard exhaust elbow has been machined

and checked for obstructions.

KEVIN STANFIELD

Cumming, Georgia

[ A ] You did an excellent job with the

intake side of the system, but in these

situations, the restriction is often in the

elbow on the outlet side. If hot water

doesn’t get out fast enough, it will cause PHOTO: COURTESY SCHRADER INTERNATIONAL

34 BOATINGMAG.COM JUNE 2016