To fix my old Yanmar 6lp or swap in 6bta or qsb380.

[Bill Stenger]

Hello all, Kind of at a turning point here with my 6lp 315 yanmar. Debating between repairing the old yammer or deciding which Cummins to install. It has 5500 hours. Here is my list of yanmar issues or things needed currently has a rust pin hole in the bottom of the oil pan, Also has an exhaust leak either in the elbow or in the exhaust housing, Injection pump and lines are quite rusty and will definitely be an issue down the road in coming years, all the coolers have not been serviced in atleast 3-4 years so they all need done.

So this may be an ideal time to install a 6bta 370 or qsb 380 before I buy 1500$ oil pan and then attack the exhaust leak which may cost me a new riser or turbo or both. Seeking your opinions on the matter. Most people don’t proclaim many high hour Yanmars. I certainly dont want to spend 3-4k$ fixing it up only for it to die soon after. So what would you gentleman do?

Boat information for decisions between 6bta370 or qsb 380. Boat is 28′ Whitewater center console. Currently has zf63 gear and 1.5″ shaft. I Believe I can get away with a 370 and the 63 gear. But I assume the qsb 380 would require a larger gear? At what Hp would I need to increase shaft size?

Thank you guys in advance. If you want specific pictures or information please let me know.

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[Bill Stenger]

Thanks Rob, i will take a look at that as soon as i get back in there. Seems like it is in the spray pattern of the raw water pump when it failed with previous owner. That plug would be a nightmare if it started spraying 100 miles into the bahamas.

[Rob Schepis]

Easiest install you could get for doing the timing belt. Based on the rust you are describing, when you’re in there do check the oil galley plug behind the injection pump that is known to rust.

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Bill Stenger

[Bill Stenger]

I have attached some pictures of the layout and fitment. Exhaust elbow is currently off, pulling the oil pan now.

Interior console dimensions at smallest spot.
41” width x 52” length. There is endless room below deck height.

Trying to fix the Yanmar up for now to try and catch the end of the calm seas here. While im shopping for an engine and planning the swap.

[Bill Stenger]

Tony, I don’t mean to frustrate you by any means! This boat does not have sealed deck hatches any where. There is 8 hatches they all have gutters but serious rain will make its way through the bilge. None of them are water tight. So yes it is a wet bilge. The boat was kept in the water for 4 years before I purchased it. There is always a 1/2″ – 1″ of water in the bilge below the pump. On the trailer is no different I jack the bow up and the drain plug is always out on the trailer. It does however always have some rain water in the bilge in front of the shaft log and under the engine.

[Tony Athens]

Wet or not?

You have water in the bilge when you leave the boat for a day, a week , or ???..

You are thinking of putting $30K+ in there, by the time the dust settles?

I won’t comment any further as it would not go over very well…

[Bill Stenger]

Rob.

I don’t really know If it would be considered wet or not. The yanmar oil pan bottom is about 8″ above the bilge at the deepest spot. Seems most of the rust damage is where a raw water pump was leaking in the past. And the bottom of the oil pan near the drain plug and dipstick. There is always some water in the bilge between rain and or seeping.

[Bill Stenger]

Tony.
1. These boats were offered from the factory with 6Bta. So I am sure they fit I have seen one installation that seemed to have decent room for service. As far as qsb is concerned that may be a shoe horn with the larger coolers and expansion tank location. I will get exact interior console measurements today. It is definitely not the driest environment in there. Yanmar oil pan is about 8″ above the bilge at most. I will update with some pictures of engine fitment and layout as well.

2. I am happy to hear you approve of the use of a 63 gear with both engines. That will make mounting easier as I likely will not have to move the gear mounts. Or buy a new coupler. I agree that 1.5 ratio seems best suited.

3. Boat is currently running a 19×22 prop with 1.5″ shaft. I may be able to step up to a 20″ but I will have to take some measurements to verify. It weighs around 8000 Lbs loaded heavy. I would really like to see 25 + Kts.

For example my last boat was a 28′ Seavee with a 250 6Bta and Vf63 @ 1.5-1 with 18×22 prop. That boat has nearly identical running surface, hull, and weight. It cruised 22Kts. @ 2300 and Wot 26-27 Kts. @ 2700.

Q1. I know I will need a larger exhaust to be fiber glassed in. Currently only has 4″ wet pipe from shower head back. Will I need 5″ or 6″?

[Rob Schepis]

If engine room is “wet” stay away from the QSB or you’ll just be adding electrical gremlins to your future issues.

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Bill Stenger, Tony Athens

[Tony Athens]

#1————————-Do you have the room to install the 6BTA or QSB5.9–Shoe-horn fits are not something you want to end up with especially in an engine room that sounds “WET”..

2) Since the engine is measurably larger is all dimensions and has a completely differ power/RPM range, you are going to be changing transmissions regardless.. If set up right in a light weight easy to “plane boat” the ZF63A has been a long term stellar performer on the back of the 370 Diamond even though it is not rated for it. I personally would have an issue using it on a QSB either, but again, you have to prop the engine light and the boat needs to be easy to plane…………………………….Your 6LP cruises in the 3000-3400 RPM rage.. The Cummins does its job in the 2200-2700 RPM range… if 2:1 now, then the Cummins would be 1.5 :1 R

3) Shaft size depends on what prop & shaft size you have now vs. what prop you will end up with to get the speed you need or expect.. Boat weight will go up at least 400 lbs

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Bill Stenger

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