Diesel I/O Running With High Temperature

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Hugs Tug

Well-known member
May 30, 2006
Reaction score
Greenport Long Island N.Y.
The owner of the house where I dock my boat has a 2002 parker with the diesel I/O package and a Bravo 3 out drive. It is the 25' walkaround model.

Two years ago the temp was running high and he was told that there was barnacle and snail growth in the 5/8 ID hose in the drive assembly along with the hose thru the transom mount.

The engine is fresh water cooled with a raw water pump on the engine to cool the heat exchanger, exhaust manifolds and risers. well the engine is starting to run on the high side again.. :cry: :cry: :cry:

My question is. Should he install a thru hull to the raw water pump and do away with the pickup in the drive? Will this alteration void the 5 year extended warranty? Or are there additionional things that need to be done to correct the inherent problem?

I have my boat at the same dock and have a Bravo 1 drive with a 5.7 Merccruiser which is all raw water cooled and have had no problems.

Any help or advice will be greatly appreciated.

Thanks in advance.

Tom, I know that we have at least one diesel owner here as well as several I/O owners, so hopefully they will check in with some insight.

Hopefully the problem can be corrected with a generic troubleshooting of FWC systems as most of the boats Parker built over the years were OB powered. That one qualifies as a "ClassicParker" all by herself!

Has your friend considered calling the factory? We have had multiple users here who have had a very good experience talking with the factory engineers. If your friend has his HIN handy, they might even be able to pull the as-builts on her.

BTW - We have been talking about starting a project here to catalog all of the various models that Parker has built over the years. That 2510 has got to be pretty unique with diesel power.

Just as the folks over at CM, the guys here love boat porn, so post some photos of that girl! :D

Thanks for the welcome and the input.
The owner has contacted White Water Marine where he purchased the boat and was told that any modifications to the boat or the power plant could very possibly jeodardize his extended warranty.

The other issue is that there are only 2 dealerships that are factory certified to work on that specific power plant.
That is the main reason for the post. To see if anyone out there has had a similiar problem and then how it was corrected.

I should have realized that all boating forums LOVE boat porn. I will shoot some pics this weekend and post with the engine specifics.

Thanks Again
Not sure if this could be the case or not, but here is my story anyway. I had a 1976 Luhrs with a 318 in it, and the boat ran pretty hot. The risers had not been cleaned or replaced in several years and a salt build up was developing in the risers. Not enough raw water was circulating to cool the freshwater in the heat exchanger. The local mechanic pulled the plugs on the manifold and scraped some of the salt build up with a close hanger. We got better water flow and the temperature dropped back 10 degrees or so. Got us to the end of the summer and we replaced the risers and manifolds over the winter. With a newer boat I would not think this would be the case yet. But might be a shot.
I have a gas 5.7 L Volvo IO, freshwater cooled.

If the hoses had growth before, check them again. Also the pickup on the drive. And if it is always in the water, prop and outdrive antifouling paint helps.

Don't bypass the water pickup through the outdrive. It cools the drive.

There's a lot of other things to check but do that first if possible.

Verify on suction side of raw water pump are tight. Is the impeller good?

2002 taken care of shouldn't need new manifolds and risers yet.

Water pump belt needs to be tight.

If you want, can take apart power steering cooler, heat exchanger and verify passages are clean.

These are a start.

I have the Merc Diesel and have never run hot. But then again I don't leave it in the water. It could be as simple as clogged intake on the drive, clogged sea strainer, bad impellers, bad coolant pump, loose belt, clogged risers etc. etc. Post the model you have. If it is a merc I can look it up in the manuel.
Andy, Dana

Thanks for the replies.
Two years ago when the problem reared its ugly head, the drive was removed and all the pickup passages were clear. The preformed hose on the transom mount along with the hose thru the mount were the culprit with the growth. Lasr fall when putting the boat up for the winter the drive was removed and checked for the growth. There was none. In the spring all system functions were checked, belts, hoses, strainers water pump and the list goes on. What we did was to pressurize the line from the transom mount and we picked up a lot of growth debris in the strainer. This was 2 weeks ago now and the engine as back to normal.
The boat is wet slipped for the season and all the necessary precautions have been taken. I have been told to use a thru hull for the pickup and use what is called a halo on the top of the drive to cool it. Has anyone heard of or used the principle?
It is the 6 cyl Mercruiser diesel. I will get the model number and post all the info.
Thanks again for the help
D-Tronic or the straight 4.2L? Parker did not put a lot of them in their boats. I know of only one other. Your engine is more than likely an Italian VM Motori block that Merc took and marineized. VM no longer does anything for Merc and Merc diesels are now Cummins engines. Parts and a good mechanic can be hard to find but your local Cummins dealer can get whatever you need for you because they have a contract to supply parts for all prior Merc Diesels. Regular Merc guys on my side don't know anything about the engine.

I have found only one Achilles heal. The crank gear is very small for a diesel and drives quite a bit. I sheared my keyway and spun the gear, bending pushrods but no valve damage. Biggest problem was down time and the 8-hour tow. Other than that mine is still running strong.
Tom, seems to me since the hose line was blown out again that the water the boat is in is conducive to growth there.

Maybe periodically do the pressurized treatment you described.

Since it sounds like the problem is in the line closer to the outdrive and not futher up to the raw water pump you may have to something since you can't flush the drive.

I added a Perko flush kit last year so if I want I can flush fresh water through the suction line through the raw water pump, the heat exchanger, exhaust manifolds and risers, and then out back out the outdrive.

Can be used with engine mount raw water pumps and not on drives that have an impeller in the outdrive.

I don't know what you refer to as a "halo" but I've seen guys with Mercruiser drives that have added external cooling lines that help cool the drive. Is that what you mean?

Dana, Andy
Going out fishing this morning. I will ret the actual specifics on the engine and post later this afternoon.
Any and all info is helpful.
Note also that there are two onther boats at the dock with I/O's, my Mako and a Pro Line. They are both salt water cooed only and neither boat has had the problem that the Parker has in 3 years. :?: :?: :?:
Thanks again
Find out if it is a 4.2 D-Tronic Mercruiser. There is a procedure for cleaning the passages in the heat exchanger.

Also find out what type antifreeze he is running. Some antifreeze is suppose to clog the passages. What is the level that he is running the coolant? Is it full to the cap?

Has the raw water impeller been changed?

Has the drive been removed and possibly not had the seals replaced that prevent the water from being pulled up the drive. Check the strainer while running to see if there are bubbles. Maybe the pump is sucking some air due to insufficient sealing.

There is always thermostat possibility. How hot is it running? Does it shut off?
Tom, as some have mentioned you can have a long list to look at but as I said you've found issues in the same plumbing twice so I would keep after this area.

For Volvo DuoProps that have some similarity (raw water pump on front of engine), here is a general list for overheating for reference.

Restricted inlet screen. Water tube guide plugged or not sealed, debris in upper gear housing, pivot housing seal damage, debris in transom nipple or transom shield water tube, failed raw water pump or hosing, thermostat or housing damaged or not put in right, loose drive belt, ignition timing too advanced or retarded, restricted passage in stern drive from being in sand or silt, engine manifold or gasket improperly damaged, installed or plugged.

These are a lot and there are more if it had raw water cooling.

It is easy to squeeze the hosing and feel the water flow and temperature from the water.

The diesel needs more cooling.

Thanks for all the sound advice.
We have been backflushing the transom mount and drive since the last overheating event and it appears that this has solved the problem, at least for now.
Stay tuned and thanks again